<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ef00b-5df3-74ec-9ad1-c6ed87369fc2,g:9218ebff-a3d6-4d57-9fef-3301cfcaa97d-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="https://xbrl.org/2023/arcrole/summation-item" xlink:type="simple" xlink:href="https://www.xbrl.org/2023/calculation-1.1.xsd#summation-item"/>
  <link:roleRef roleURI="http://powersint.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="psix-20260630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:calculationLink xlink:role="http://powersint.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef00b-5f68-7aef-8f18-fb0258b6e35c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef00b-5f68-7aef-8f18-fb0258b6e35c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019ef00b-5f68-7f3d-aec4-2421b557b24a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_RestrictedCashCurrent_019ef00b-5f68-7f3d-aec4-2421b557b24a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019ef00b-5f68-709b-8bac-d7c0471d3f56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019ef00b-5f68-709b-8bac-d7c0471d3f56" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivable_019ef00b-5f68-7d34-bb22-988fc8877f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxesReceivable"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_IncomeTaxesReceivable_019ef00b-5f68-7d34-bb22-988fc8877f0d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019ef00b-5f68-7dc1-bcea-eb7395a63ef5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_InventoryNet_019ef00b-5f68-7dc1-bcea-eb7395a63ef5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_019ef00b-5f68-7dde-ab06-b1a201e16a3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_019ef00b-5f68-7dde-ab06-b1a201e16a3e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ef00b-5f68-713f-838c-18fd9a56849d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ef00b-5f68-713f-838c-18fd9a56849d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_019ef00b-5f68-7f8a-8ea4-631280e21b60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7199-aa27-70a00236b997" xlink:to="loc_us-gaap_OtherAssetsCurrent_019ef00b-5f68-7f8a-8ea4-631280e21b60" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef00b-5f68-7e2f-945a-8857e55b6865" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019ef00b-5f68-7dfb-8091-b8ecc98121e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef00b-5f68-7e2f-945a-8857e55b6865" xlink:to="loc_us-gaap_Liabilities_019ef00b-5f68-7dfb-8091-b8ecc98121e6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ef00b-5f68-78f5-a203-3b0f5274e362" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef00b-5f68-7e2f-945a-8857e55b6865" xlink:to="loc_us-gaap_StockholdersEquity_019ef00b-5f68-78f5-a203-3b0f5274e362" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019ef00b-5f68-7b82-b737-9093f77a9f72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019ef00b-5f68-7e2f-945a-8857e55b6865" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019ef00b-5f68-7b82-b737-9093f77a9f72" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7d82-8be3-d6f34ff6063f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_AssetsCurrent_019ef00b-5f68-7d82-8be3-d6f34ff6063f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019ef00b-5f68-7175-b765-a12759c17a81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019ef00b-5f68-7175-b765-a12759c17a81" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019ef00b-5f68-776a-a2db-5f1585750197" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019ef00b-5f68-776a-a2db-5f1585750197" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019ef00b-5f68-7226-bbfc-274dfdcd1e26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019ef00b-5f68-7226-bbfc-274dfdcd1e26" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019ef00b-5f68-7de7-8041-bbdba172b0fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_Goodwill_019ef00b-5f68-7de7-8041-bbdba172b0fb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019ef00b-5f68-73d1-a89e-8042bb681d86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019ef00b-5f68-73d1-a89e-8042bb681d86" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019ef00b-5f68-74a0-aa0e-f2a44e4136af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019ef00b-5f68-74a0-aa0e-f2a44e4136af" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsAssetsNoncurrent_019ef00b-5f68-7abc-a42e-26c9b91b3cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepositsAssetsNoncurrent"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019ef00b-5f68-7fb4-a495-f483be5475d0" xlink:to="loc_us-gaap_DepositsAssetsNoncurrent_019ef00b-5f68-7abc-a42e-26c9b91b3cf7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019ef00b-5f68-7d36-87e9-7a173200815a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019ef00b-5f68-7d36-87e9-7a173200815a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019ef00b-5f68-7a78-b400-91f09c3f87cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019ef00b-5f68-7a78-b400-91f09c3f87cd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019ef00b-5f68-7778-9755-b244983c4459" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019ef00b-5f68-7778-9755-b244983c4459" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019ef00b-5f68-72d9-b2d5-9cd0615bd80d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019ef00b-5f68-72d9-b2d5-9cd0615bd80d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_019ef00b-5f68-759f-bbd2-4475d00226e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_019ef00b-5f68-759f-bbd2-4475d00226e9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-7bcc-90d7-d1684aee07bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-7bcc-90d7-d1684aee07bb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermLineOfCredit_019ef00b-5f68-78ee-8f5a-76b8e59bfa8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermLineOfCredit"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019ef00b-5f68-7256-a0fe-87261b38ad57" xlink:to="loc_us-gaap_LongTermLineOfCredit_019ef00b-5f68-78ee-8f5a-76b8e59bfa8e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_019ef00b-5f68-7b47-ba7b-0b58cda867c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_AccountsPayableCurrent_019ef00b-5f68-7b47-ba7b-0b58cda867c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_IEEPATariffRefundLiabilityCurrent_019ef00b-5f68-7bcd-a774-0fc576ffb1e9" xlink:href="psix-20260630.xsd#psix_IEEPATariffRefundLiabilityCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_psix_IEEPATariffRefundLiabilityCurrent_019ef00b-5f68-7bcd-a774-0fc576ffb1e9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019ef00b-5f68-7dff-9552-c29abe52a99c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_LongTermDebtCurrent_019ef00b-5f68-7dff-9552-c29abe52a99c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityCurrent_019ef00b-5f68-7f7c-b564-85a0941c3022" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_FinanceLeaseLiabilityCurrent_019ef00b-5f68-7f7c-b564-85a0941c3022" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019ef00b-5f68-7847-ba33-ccedebe72205" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019ef00b-5f68-7847-ba33-ccedebe72205" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermBorrowings_019f7e0b-689e-74db-b269-a6794805eee4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherShortTermBorrowings"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_OtherShortTermBorrowings_019f7e0b-689e-74db-b269-a6794805eee4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019fd10f-347b-7cfb-afff-96deebf6ca01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_019ef00b-5f68-79eb-8e7d-57e1e8c2d7ed" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019fd10f-347b-7cfb-afff-96deebf6ca01" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ef00b-5f68-7d81-8e98-8ecf59969195" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019ef00b-5f68-709f-b7cd-b1631de89ed1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef00b-5f68-7d81-8e98-8ecf59969195" xlink:to="loc_us-gaap_CommonStockValue_019ef00b-5f68-709f-b7cd-b1631de89ed1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019ef00b-5f68-74fb-b321-97bfea013991" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef00b-5f68-7d81-8e98-8ecf59969195" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019ef00b-5f68-74fb-b321-97bfea013991" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef00b-5f68-7a2b-a33d-d744659a58b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef00b-5f68-7d81-8e98-8ecf59969195" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019ef00b-5f68-7a2b-a33d-d744659a58b2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_019ef00b-5f68-74e4-8826-0e9fb3d01f1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019ef00b-5f68-7d81-8e98-8ecf59969195" xlink:to="loc_us-gaap_TreasuryStockCommonValue_019ef00b-5f68-74e4-8826-0e9fb3d01f1b" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMEUNAUDITED" xlink:type="simple" xlink:href="psix-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMEUNAUDITED"/>
  <link:calculationLink xlink:role="http://powersint.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMEUNAUDITED" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019ef00b-5f68-7cd2-808f-a97a7fc0a400" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019ef00b-5f68-7e49-ba3a-c4308c159283" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019ef00b-5f68-7cd2-808f-a97a7fc0a400" xlink:to="loc_us-gaap_GrossProfit_019ef00b-5f68-7e49-ba3a-c4308c159283" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7479-9b67-0222760550b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_019ef00b-5f68-7cd2-808f-a97a7fc0a400" xlink:to="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7479-9b67-0222760550b0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ef00b-5f68-7411-abc9-10ea632e9cde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ef00b-5f68-7f1b-a0ee-783006664d5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019ef00b-5f68-7411-abc9-10ea632e9cde" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ef00b-5f68-7f1b-a0ee-783006664d5a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019ef00b-5f68-742f-b0c9-3a63cc50e580" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019ef00b-5f68-7411-abc9-10ea632e9cde" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019ef00b-5f68-742f-b0c9-3a63cc50e580" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7c78-a220-3db787e31a46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019ef00b-5f68-7f62-9651-e9cca9a0e369" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7c78-a220-3db787e31a46" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019ef00b-5f68-7f62-9651-e9cca9a0e369" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ef00b-5f68-7a0f-a19a-bf86e6af16ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7c78-a220-3db787e31a46" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ef00b-5f68-7a0f-a19a-bf86e6af16ce" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019ef00b-5f68-7d76-81fe-14384e77da4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingExpenses_019ef00b-5f68-7c78-a220-3db787e31a46" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019ef00b-5f68-7d76-81fe-14384e77da4a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019ef00b-5f68-777c-b233-ce54bea78049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ef00b-5f68-7458-abaa-06fb8a65df38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019ef00b-5f68-777c-b233-ce54bea78049" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ef00b-5f68-7458-abaa-06fb8a65df38" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019ef00b-5f68-7788-84f9-a78a8d6d1ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_GrossProfit_019ef00b-5f68-777c-b233-ce54bea78049" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019ef00b-5f68-7788-84f9-a78a8d6d1ad4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019ef00b-5f68-76ee-96bb-babc619ea168" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019ef00b-5f68-7318-9b7f-30ec444ebcda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_019ef00b-5f68-76ee-96bb-babc619ea168" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019ef00b-5f68-7318-9b7f-30ec444ebcda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019ef00b-5f68-7603-ad1b-49ddb036a95f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_019ef00b-5f68-76ee-96bb-babc619ea168" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019ef00b-5f68-7603-ad1b-49ddb036a95f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ef00b-5f68-73ed-857c-b7208f0e7d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019ef00b-5f68-71d4-835a-b90973958fff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ef00b-5f68-73ed-857c-b7208f0e7d0a" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_019ef00b-5f68-71d4-835a-b90973958fff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019ef00b-5f68-7d47-b946-c3b86e519cea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ef00b-5f68-73ed-857c-b7208f0e7d0a" xlink:to="loc_us-gaap_OperatingIncomeLoss_019ef00b-5f68-7d47-b946-c3b86e519cea" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSUNAUDITED" xlink:type="simple" xlink:href="psix-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSUNAUDITED"/>
  <link:calculationLink xlink:role="http://powersint.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSUNAUDITED" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-714e-9a8f-d2eb45595869" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities_019ef00b-5f68-7e68-bbef-347995b29a79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-714e-9a8f-d2eb45595869" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities_019ef00b-5f68-7e68-bbef-347995b29a79" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfShortTermDebt_019ef00b-5f68-7676-86a1-308d2ea548b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfShortTermDebt"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-714e-9a8f-d2eb45595869" xlink:to="loc_us-gaap_RepaymentsOfShortTermDebt_019ef00b-5f68-7676-86a1-308d2ea548b6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019ef00b-5f68-725a-b8fa-d8492449e422" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-714e-9a8f-d2eb45595869" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_019ef00b-5f68-725a-b8fa-d8492449e422" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019ef00b-5f68-7410-be44-82051cc02a42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-714e-9a8f-d2eb45595869" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019ef00b-5f68-7410-be44-82051cc02a42" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_019ef00b-5f68-748c-a985-eb323dc20ed3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherOperatingActivitiesCashFlowStatement"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_019ef00b-5f68-748c-a985-eb323dc20ed3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_019ef00b-5f68-7c17-a146-918f21d9e447" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_019ef00b-5f68-7c17-a146-918f21d9e447" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019ef00b-5f68-7d6c-9eac-ae6830d57fd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019ef00b-5f68-7d6c-9eac-ae6830d57fd8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_IncreaseDecreaseInAllowanceForObsolescence_019ef00b-5f68-7958-8513-d472e7416296" xlink:href="psix-20260630.xsd#psix_IncreaseDecreaseInAllowanceForObsolescence"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_psix_IncreaseDecreaseInAllowanceForObsolescence_019ef00b-5f68-7958-8513-d472e7416296" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_019ef00b-5f68-7a95-b196-ff38dc271555" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_019ef00b-5f68-7a95-b196-ff38dc271555" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_019ef00b-5f68-703b-b3f4-d01cea804f0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_019ef00b-5f68-703b-b3f4-d01cea804f0f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_019ef00b-5f68-798c-ab80-56b3c3b307ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_019ef00b-5f68-798c-ab80-56b3c3b307ae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable_019ef00b-5f68-7227-b85d-8e506877adb3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInIncomeTaxesPayableNetOfIncomeTaxesReceivable_019ef00b-5f68-7227-b85d-8e506877adb3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_019ef00b-5f68-7dc0-94b4-ae7b2e51d087" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_019ef00b-5f68-7dc0-94b4-ae7b2e51d087" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ef00b-5f68-739c-b3b9-f8a311835f15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_NetIncomeLoss_019ef00b-5f68-739c-b3b9-f8a311835f15" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_019ef00b-5f68-77e8-b380-b1f64c677733" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_019ef00b-5f68-77e8-b380-b1f64c677733" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019ef00b-5f68-7d37-9b82-ff062e5320d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_DeferredIncomeTaxesAndTaxCredits_019ef00b-5f68-7d37-9b82-ff062e5320d4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019ef00b-5f68-7a62-afd7-594af49b2226" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019ef00b-5f68-7a62-afd7-594af49b2226" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019ef00b-5f68-7d46-b266-e69bf91ba27e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:calculationArc order="14" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019ef00b-5f68-7d46-b266-e69bf91ba27e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_019ef00b-5f68-79db-8237-25f4344d6f0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Depreciation"/>
    <link:calculationArc order="15" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_Depreciation_019ef00b-5f68-79db-8237-25f4344d6f0f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_019ef00b-5f68-7b54-9f59-7e65184caac2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPrepaidExpense"/>
    <link:calculationArc order="16" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_019ef00b-5f68-7b54-9f59-7e65184caac2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019ef00b-5f68-7633-be5c-7094b3e6f3b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:calculationArc order="17" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_019ef00b-5f68-7633-be5c-7094b3e6f3b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019ef00b-5f68-74c0-8907-f4e1b3041a69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="18" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019ef00b-5f68-74c0-8907-f4e1b3041a69" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019ef00b-5f68-716a-8f73-ef1694a6e777" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="19" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_us-gaap_ShareBasedCompensation_019ef00b-5f68-716a-8f73-ef1694a6e777" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_IncreaseDecreaseInIEEPATariffRefundLiability_019fd112-e78f-72c3-ab37-8770f0008972" xlink:href="psix-20260630.xsd#psix_IncreaseDecreaseInIEEPATariffRefundLiability"/>
    <link:calculationArc order="20" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-727a-9cd9-c9b06c10c049" xlink:to="loc_psix_IncreaseDecreaseInIEEPATariffRefundLiability_019fd112-e78f-72c3-ab37-8770f0008972" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019ef00b-5f68-75f3-b436-80e4b85cdd35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-768b-a88d-b4945cebf6f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019ef00b-5f68-75f3-b436-80e4b85cdd35" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019ef00b-5f68-768b-a88d-b4945cebf6f7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-716a-a17e-1228fbe89fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019ef00b-5f68-75f3-b436-80e4b85cdd35" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-716a-a17e-1228fbe89fe7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-7f96-8bc7-e90de2cc64a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019ef00b-5f68-75f3-b436-80e4b85cdd35" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019ef00b-5f68-7f96-8bc7-e90de2cc64a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-7add-befe-680f4802252b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForCapitalImprovements_019ef00b-5f68-7a19-a948-1e4aedf3e734" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForCapitalImprovements"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-7add-befe-680f4802252b" xlink:to="loc_us-gaap_PaymentsForCapitalImprovements_019ef00b-5f68-7a19-a948-1e4aedf3e734" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_019ef00b-5f68-7154-ae78-f4fc7102f5be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfProductiveAssets"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-7add-befe-680f4802252b" xlink:to="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_019ef00b-5f68-7154-ae78-f4fc7102f5be" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019f6434-ca44-7fb3-972a-4329175f930a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019ef00b-5f68-7add-befe-680f4802252b" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019f6434-ca44-7fb3-972a-4329175f930a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef00b-5f68-734f-b480-13d9ab84bc8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef00b-5f68-7cc1-8ce8-b2f93394c906" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef00b-5f68-734f-b480-13d9ab84bc8b" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019ef00b-5f68-7cc1-8ce8-b2f93394c906" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_019ef00b-5f68-7e4c-b62a-12b6edc2037a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019ef00b-5f68-734f-b480-13d9ab84bc8b" xlink:to="loc_us-gaap_RestrictedCashCurrent_019ef00b-5f68-7e4c-b62a-12b6edc2037a" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofInventoryandActivityinInventoryAllowanceDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofInventoryandActivityinInventoryAllowanceDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofInventoryandActivityinInventoryAllowanceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_019ef00b-5f68-77d3-8a13-924b3fce23a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryGross"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRawMaterials_019ef00b-5f68-724b-bacc-c2fc2eeb62b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryRawMaterials"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryGross_019ef00b-5f68-77d3-8a13-924b3fce23a0" xlink:to="loc_us-gaap_InventoryRawMaterials_019ef00b-5f68-724b-bacc-c2fc2eeb62b6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWorkInProcess_019ef00b-5f68-78c3-bae3-9bdb8bee5bac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryWorkInProcess"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryGross_019ef00b-5f68-77d3-8a13-924b3fce23a0" xlink:to="loc_us-gaap_InventoryWorkInProcess_019ef00b-5f68-78c3-bae3-9bdb8bee5bac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoods_019ef00b-5f68-736d-ae6b-96e2917f46f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryFinishedGoods"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryGross_019ef00b-5f68-77d3-8a13-924b3fce23a0" xlink:to="loc_us-gaap_InventoryFinishedGoods_019ef00b-5f68-736d-ae6b-96e2917f46f6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_019ef00b-5f68-7c24-9061-ec1354786093" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_019ef00b-5f68-7956-a054-66c27d4c260e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_019ef00b-5f68-7c24-9061-ec1354786093" xlink:to="loc_us-gaap_InventoryGross_019ef00b-5f68-7956-a054-66c27d4c260e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryValuationReserves_019ef00b-5f68-7250-8ec6-e83899d7cd9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InventoryValuationReserves"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_019ef00b-5f68-7c24-9061-ec1354786093" xlink:to="loc_us-gaap_InventoryValuationReserves_019ef00b-5f68-7250-8ec6-e83899d7cd9e" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofOtherAccruedLiabilitiesDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofOtherAccruedLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofOtherAccruedLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandardProductWarrantyAccrualCurrent_019ef00b-5f68-7395-bbfc-f6a3bad2c64e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StandardProductWarrantyAccrualCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_StandardProductWarrantyAccrualCurrent_019ef00b-5f68-7395-bbfc-f6a3bad2c64e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserveCurrent_019ef00b-5f68-75f7-9fc1-9191f501e459" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserveCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_LitigationReserveCurrent_019ef00b-5f68-75f7-9fc1-9191f501e459" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ef00b-5f68-78b7-9aee-71bea23bd2d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ef00b-5f68-78b7-9aee-71bea23bd2d4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedEmployeeBenefitsCurrent_019ef00b-5f68-7bec-8077-697759c488f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedEmployeeBenefitsCurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_AccruedEmployeeBenefitsCurrent_019ef00b-5f68-7bec-8077-697759c488f7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrent_019ef00b-5f68-775f-b3cb-9fbcc51e9031" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPayableCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_InterestPayableCurrent_019ef00b-5f68-775f-b3cb-9fbcc51e9031" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherEmployeeRelatedLiabilitiesCurrent_019ef00b-5f68-713f-b8c0-4bc0ee241941" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherEmployeeRelatedLiabilitiesCurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_OtherEmployeeRelatedLiabilitiesCurrent_019ef00b-5f68-713f-b8c0-4bc0ee241941" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableCurrent_019ef00b-5f68-7d1d-912a-fb93e8e759f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayableCurrent"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_NotesPayableCurrent_019ef00b-5f68-7d1d-912a-fb93e8e759f2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_CustomsAccrualCurrent_019ef00b-5f68-7a6e-98b4-bbc51f83ccc3" xlink:href="psix-20260630.xsd#psix_CustomsAccrualCurrent"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_psix_CustomsAccrualCurrent_019ef00b-5f68-7a6e-98b4-bbc51f83ccc3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxesPayableCurrent_019ef00b-5f68-7ef3-a561-b60558999cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TaxesPayableCurrent"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_TaxesPayableCurrent_019ef00b-5f68-7ef3-a561-b60558999cd9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherSundryLiabilitiesCurrent_019ef00b-5f68-7231-aafb-fcd296ed1c83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherSundryLiabilitiesCurrent"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherAccruedLiabilitiesCurrent_019ef00b-5f68-7698-9a68-7078c735d422" xlink:to="loc_us-gaap_OtherSundryLiabilitiesCurrent_019ef00b-5f68-7231-aafb-fcd296ed1c83" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofAccruedProductWarrantyActivitiesDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofAccruedProductWarrantyActivitiesDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/SummaryofSignificantAccountingPoliciesandOtherInformationScheduleofAccruedProductWarrantyActivitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandardProductWarrantyAccrual_019ef00b-5f68-77bd-80ab-8e4dbc17435b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StandardProductWarrantyAccrual"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandardProductWarrantyAccrualNoncurrent_019ef00b-5f68-7873-baa4-2c46a8ec3d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StandardProductWarrantyAccrualNoncurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StandardProductWarrantyAccrual_019ef00b-5f68-77bd-80ab-8e4dbc17435b" xlink:to="loc_us-gaap_StandardProductWarrantyAccrualNoncurrent_019ef00b-5f68-7873-baa4-2c46a8ec3d8e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandardProductWarrantyAccrualCurrent_019ef00b-5f68-71b9-8229-f9829a52aeff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StandardProductWarrantyAccrualCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StandardProductWarrantyAccrual_019ef00b-5f68-77bd-80ab-8e4dbc17435b" xlink:to="loc_us-gaap_StandardProductWarrantyAccrualCurrent_019ef00b-5f68-71b9-8229-f9829a52aeff" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/BusinessCombinationScheduleofPreliminaryPurchasePriceDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#BusinessCombinationScheduleofPreliminaryPurchasePriceDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/BusinessCombinationScheduleofPreliminaryPurchasePriceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_psix_BusinessCombinationAggregateConsiderationTransferred_019ef00b-5f68-7ebe-b21a-bb8812c54aa6" xlink:href="psix-20260630.xsd#psix_BusinessCombinationAggregateConsiderationTransferred"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019ef00b-5f68-7a34-b0a1-21e5f9365e9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_BusinessCombinationAggregateConsiderationTransferred_019ef00b-5f68-7ebe-b21a-bb8812c54aa6" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019ef00b-5f68-7a34-b0a1-21e5f9365e9f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_019ef00b-5f68-7825-a7ef-713af340dcf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_BusinessCombinationAggregateConsiderationTransferred_019ef00b-5f68-7ebe-b21a-bb8812c54aa6" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_019ef00b-5f68-7825-a7ef-713af340dcf4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_BusinessCombinationConsiderationTransferredWorkingCapitalAndOtherAdjustments_019ef00b-5f68-7ce6-b102-fda540179c02" xlink:href="psix-20260630.xsd#psix_BusinessCombinationConsiderationTransferredWorkingCapitalAndOtherAdjustments"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_BusinessCombinationAggregateConsiderationTransferred_019ef00b-5f68-7ebe-b21a-bb8812c54aa6" xlink:to="loc_psix_BusinessCombinationConsiderationTransferredWorkingCapitalAndOtherAdjustments_019ef00b-5f68-7ce6-b102-fda540179c02" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/BusinessCombinationScheduleofComponentsofPreliminaryPurchasePriceDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#BusinessCombinationScheduleofComponentsofPreliminaryPurchasePriceDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/BusinessCombinationScheduleofComponentsofPreliminaryPurchasePriceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ef00b-5f68-7b77-99fe-2383272aec12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-72de-b5c9-b20e331541b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ef00b-5f68-7b77-99fe-2383272aec12" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-72de-b5c9-b20e331541b0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019ef00b-5f68-7858-93b9-32f68c67d5a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019ef00b-5f68-7b77-99fe-2383272aec12" xlink:to="loc_us-gaap_Goodwill_019ef00b-5f68-7858-93b9-32f68c67d5a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019ef00b-5f68-77ae-bd0a-bb3b59d8d3e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019ef00b-5f68-77ae-bd0a-bb3b59d8d3e4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019ef00b-5f68-7711-9df2-1fd83883b23e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_019ef00b-5f68-7711-9df2-1fd83883b23e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019ef00b-5f68-7d62-b964-861acb63ffda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019ef00b-5f68-7d62-b964-861acb63ffda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019ef00b-5f68-735e-b0a6-e6c1bd0236dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019ef00b-5f68-735e-b0a6-e6c1bd0236dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_BusinessCombinationRecognizedAssetAcquiredOperatingLeaseRightOfUseAsset_019ef00b-5f68-7bf4-847d-06481bd03053" xlink:href="psix-20260630.xsd#psix_BusinessCombinationRecognizedAssetAcquiredOperatingLeaseRightOfUseAsset"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_psix_BusinessCombinationRecognizedAssetAcquiredOperatingLeaseRightOfUseAsset_019ef00b-5f68-7bf4-847d-06481bd03053" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019ef00b-5f68-769c-b1ff-86bcec4002c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019ef00b-5f68-769c-b1ff-86bcec4002c7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_BusinessCombinationRecognizedLiabilityAssumedAccountsPayableAndOtherAccruedLiabilitiesCurrent_019ef00b-5f68-7c51-ac31-8d4da8e49c1b" xlink:href="psix-20260630.xsd#psix_BusinessCombinationRecognizedLiabilityAssumedAccountsPayableAndOtherAccruedLiabilitiesCurrent"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_psix_BusinessCombinationRecognizedLiabilityAssumedAccountsPayableAndOtherAccruedLiabilitiesCurrent_019ef00b-5f68-7c51-ac31-8d4da8e49c1b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019ef00b-5f68-7d20-b897-c515e12f275e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019ef00b-5f68-7d20-b897-c515e12f275e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiability_019ef00b-5f68-7b74-baf3-57a5ad500089" xlink:href="psix-20260630.xsd#psix_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiability"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019ef00b-5f68-7e97-ad23-100427c239a7" xlink:to="loc_psix_BusinessCombinationRecognizedLiabilityAssumedOperatingLeaseLiability_019ef00b-5f68-7b74-baf3-57a5ad500089" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/RevenueScheduleofContractBalancesDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#RevenueScheduleofContractBalancesDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/RevenueScheduleofContractBalancesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_psix_ContractWithCustomerAssetLiability_019ef00b-5f68-7b1b-b885-76f7df188377" xlink:href="psix-20260630.xsd#psix_ContractWithCustomerAssetLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ef00b-5f68-70f9-830f-bdda83d6649f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_ContractWithCustomerAssetLiability_019ef00b-5f68-7b1b-b885-76f7df188377" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_019ef00b-5f68-70f9-830f-bdda83d6649f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ef00b-5f68-7004-b6f6-a26324afbaaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_ContractWithCustomerAssetLiability_019ef00b-5f68-7b1b-b885-76f7df188377" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019ef00b-5f68-7004-b6f6-a26324afbaaa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_019ef00b-5f68-7ecf-9a85-b0e33449de3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_psix_ContractWithCustomerAssetLiability_019ef00b-5f68-7b1b-b885-76f7df188377" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_019ef00b-5f68-7ecf-9a85-b0e33449de3e" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/PropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#PropertyPlantandEquipmentDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/PropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019ef00b-5f68-72bd-bc0f-f4bf5a1a4880" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019ef00b-5f68-7450-b0ef-d7e47c9b09d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019ef00b-5f68-72bd-bc0f-f4bf5a1a4880" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019ef00b-5f68-7450-b0ef-d7e47c9b09d7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019ef00b-5f68-79e1-8636-dd73d8dc9614" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019ef00b-5f68-72bd-bc0f-f4bf5a1a4880" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019ef00b-5f68-79e1-8636-dd73d8dc9614" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/GoodwillandOtherIntangiblesScheduleofComponentsofIntangibleAssetsDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#GoodwillandOtherIntangiblesScheduleofComponentsofIntangibleAssetsDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/GoodwillandOtherIntangiblesScheduleofComponentsofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019ef00b-5f68-728a-96cb-2ee82626d4d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019ef00b-5f68-7b75-97db-6ae0c9ea66d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019ef00b-5f68-728a-96cb-2ee82626d4d5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019ef00b-5f68-7b75-97db-6ae0c9ea66d3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019ef00b-5f68-7480-964d-728847542207" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019ef00b-5f68-728a-96cb-2ee82626d4d5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019ef00b-5f68-7480-964d-728847542207" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/DebtScheduleofOutstandingDebtDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#DebtScheduleofOutstandingDebtDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/DebtScheduleofOutstandingDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-77fa-a51f-a48772d38e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_019ef00b-5f69-727a-b007-77a6002fa472" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-77fa-a51f-a48772d38e5b" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_019ef00b-5f69-727a-b007-77a6002fa472" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_LongTermDebtExcludingNotesPayable_019ef00b-5f69-7b0d-8d39-ada753ec1612" xlink:href="psix-20260630.xsd#psix_LongTermDebtExcludingNotesPayable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-77fa-a51f-a48772d38e5b" xlink:to="loc_psix_LongTermDebtExcludingNotesPayable_019ef00b-5f69-7b0d-8d39-ada753ec1612" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/DebtScheduleofOutstandingDebtDetails_1" xlink:type="simple" xlink:href="psix-20260630.xsd#DebtScheduleofOutstandingDebtDetails_1"/>
  <link:calculationLink xlink:role="http://powersint.com/role/DebtScheduleofOutstandingDebtDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-72ab-9305-11f0896a7827" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_FinanceLeaseLiabilityAndOtherLongTermDebt_019ef00b-5f69-7ac8-a13a-15bc58eab1ff" xlink:href="psix-20260630.xsd#psix_FinanceLeaseLiabilityAndOtherLongTermDebt"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-72ab-9305-11f0896a7827" xlink:to="loc_psix_FinanceLeaseLiabilityAndOtherLongTermDebt_019ef00b-5f69-7ac8-a13a-15bc58eab1ff" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ef00b-5f69-7472-a336-3561e9b4109c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019ef00b-5f69-72ab-9305-11f0896a7827" xlink:to="loc_us-gaap_LongTermDebt_019ef00b-5f69-7472-a336-3561e9b4109c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/OtherNonCurrentLiabilitiesScheduleofNotePayableDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#OtherNonCurrentLiabilitiesScheduleofNotePayableDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/OtherNonCurrentLiabilitiesScheduleofNotePayableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ef00b-5f69-755a-b920-f2b87b28fc67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-7ce1-839e-aff7ffe7b389" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019ef00b-5f69-755a-b920-f2b87b28fc67" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-7ce1-839e-aff7ffe7b389" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7580-93c3-2e117ccb8f71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_019ef00b-5f69-755a-b920-f2b87b28fc67" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7580-93c3-2e117ccb8f71" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/OtherNonCurrentLiabilitiesScheduleofRemainingMaturitiesofLongTermDebtDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#OtherNonCurrentLiabilitiesScheduleofRemainingMaturitiesofLongTermDebtDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/OtherNonCurrentLiabilitiesScheduleofRemainingMaturitiesofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-750c-9671-c73679879901" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019ef00b-5f69-7811-8144-129b2a93425b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-750c-9671-c73679879901" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_019ef00b-5f69-7811-8144-129b2a93425b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019ef00b-5f69-7ad3-9493-7a88037bf774" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-750c-9671-c73679879901" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_019ef00b-5f69-7ad3-9493-7a88037bf774" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019ef00b-5f69-78a3-87ef-56f95a952b0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentCarryingAmount_019ef00b-5f69-750c-9671-c73679879901" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_019ef00b-5f69-78a3-87ef-56f95a952b0a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7f93-9c35-18a3e0ef108a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_AmortizationOfDebtDiscountPremiumYearTwo_019ef00b-5f69-7398-8471-d30651341849" xlink:href="psix-20260630.xsd#psix_AmortizationOfDebtDiscountPremiumYearTwo"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7f93-9c35-18a3e0ef108a" xlink:to="loc_psix_AmortizationOfDebtDiscountPremiumYearTwo_019ef00b-5f69-7398-8471-d30651341849" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_AmortizationOfDebtDiscountPremiumYearOne_019ef00b-5f69-7deb-9861-f463f98e9dc7" xlink:href="psix-20260630.xsd#psix_AmortizationOfDebtDiscountPremiumYearOne"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7f93-9c35-18a3e0ef108a" xlink:to="loc_psix_AmortizationOfDebtDiscountPremiumYearOne_019ef00b-5f69-7deb-9861-f463f98e9dc7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_psix_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear_019ef00b-5f69-7cd1-bd87-d5284c4b717f" xlink:href="psix-20260630.xsd#psix_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019ef00b-5f69-7f93-9c35-18a3e0ef108a" xlink:to="loc_psix_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear_019ef00b-5f69-7cd1-bd87-d5284c4b717f" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/LeasesScheduleofComponentsofLeaseExpenseDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#LeasesScheduleofComponentsofLeaseExpenseDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/LeasesScheduleofComponentsofLeaseExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LeaseCost"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019ef00b-5f69-797f-876a-17c5f19f8ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:to="loc_us-gaap_OperatingLeaseCost_019ef00b-5f69-797f-876a-17c5f19f8ca6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019ef00b-5f69-7c2a-8fe4-cae1de521831" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseRightOfUseAssetAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetAmortization_019ef00b-5f69-7c2a-8fe4-cae1de521831" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseInterestExpense_019ef00b-5f69-7216-a2a6-d5f65f88f138" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseInterestExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:to="loc_us-gaap_FinanceLeaseInterestExpense_019ef00b-5f69-7216-a2a6-d5f65f88f138" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermLeaseCost_019ef00b-5f69-7e04-9ae6-9f146c8e7c08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermLeaseCost"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:to="loc_us-gaap_ShortTermLeaseCost_019ef00b-5f69-7e04-9ae6-9f146c8e7c08" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableLeaseCost_019ef00b-5f69-731f-a118-1976122eae8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableLeaseCost"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LeaseCost_019ef00b-5f69-7a8d-85c3-3a7681fd3983" xlink:to="loc_us-gaap_VariableLeaseCost_019ef00b-5f69-731f-a118-1976122eae8b" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/LeasesScheduleofSupplementalBalanceSheetInformationRelatedtoLeasesDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#LeasesScheduleofSupplementalBalanceSheetInformationRelatedtoLeasesDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/LeasesScheduleofSupplementalBalanceSheetInformationRelatedtoLeasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019ef00b-5f69-776c-919f-2bf39b384e6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019ef00b-5f69-7ec9-9fb1-4fdf8d9b811e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeaseLiability_019ef00b-5f69-776c-919f-2bf39b384e6c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019ef00b-5f69-7ec9-9fb1-4fdf8d9b811e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019ef00b-5f69-7fe2-a69b-5a8350f96709" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeaseLiability_019ef00b-5f69-776c-919f-2bf39b384e6c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019ef00b-5f69-7fe2-a69b-5a8350f96709" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_019ef00b-5f69-77ad-9cbb-09cf90b671aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityCurrent_019ef00b-5f69-7f64-b250-1e73d540bb18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiability_019ef00b-5f69-77ad-9cbb-09cf90b671aa" xlink:to="loc_us-gaap_FinanceLeaseLiabilityCurrent_019ef00b-5f69-7f64-b250-1e73d540bb18" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019ef00b-5f69-7a1c-ac8c-47814b125f1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityNoncurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiability_019ef00b-5f69-77ad-9cbb-09cf90b671aa" xlink:to="loc_us-gaap_FinanceLeaseLiabilityNoncurrent_019ef00b-5f69-7a1c-ac8c-47814b125f1e" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019ef00b-601e-7333-a81c-725257a4c416" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_019ef00b-601e-7333-a81c-725257a4c416" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019ef00b-601e-71e8-8f80-18d02eaf86e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_019ef00b-601e-71e8-8f80-18d02eaf86e4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019ef00b-601e-7dfe-99f5-172f73e0b290" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_019ef00b-601e-7dfe-99f5-172f73e0b290" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019ef00b-601e-7e30-afab-abe1f46a401c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_019ef00b-601e-7e30-afab-abe1f46a401c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019ef00b-601e-7271-b8e4-5bd89d5ffd4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_019ef00b-601e-7271-b8e4-5bd89d5ffd4f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019ef00b-601e-7952-addd-abd2f4c01cd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_019ef00b-601e-7952-addd-abd2f4c01cd7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019ef00b-601e-78c5-a78c-508d7729a623" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7422-b526-74be8a97f8f4" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_019ef00b-601e-78c5-a78c-508d7729a623" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7bf0-bf47-c611df72a0e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_019ef00b-601e-709b-be42-a84b4eee7477" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7bf0-bf47-c611df72a0e3" xlink:to="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_019ef00b-601e-709b-be42-a84b4eee7477" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_019ef00b-601e-740f-b3c9-9edd0c6f7c40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7bf0-bf47-c611df72a0e3" xlink:to="loc_us-gaap_FinanceLeaseLiability_019ef00b-601e-740f-b3c9-9edd0c6f7c40" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails_1" xlink:type="simple" xlink:href="psix-20260630.xsd#LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails_1"/>
  <link:calculationLink xlink:role="http://powersint.com/role/LeasesScheduleofMaturityAnalysisofLeaseLiabilitiesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7b26-bfcf-08430b817a6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019ef00b-601e-72fb-b3ee-2e35903acb07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7b26-bfcf-08430b817a6d" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_019ef00b-601e-72fb-b3ee-2e35903acb07" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019ef00b-601e-7fe2-a3fc-276b0c7036ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_019ef00b-601e-7b26-bfcf-08430b817a6d" xlink:to="loc_us-gaap_OperatingLeaseLiability_019ef00b-601e-7fe2-a3fc-276b0c7036ad" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_019ef00b-601e-7898-87ae-91444326fdd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear_019ef00b-601e-7898-87ae-91444326fdd9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_019ef00b-601e-7df0-b6d2-89409637fcd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_019ef00b-601e-7df0-b6d2-89409637fcd9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019ef00b-601e-71bd-b3b6-dee3c668a9dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_019ef00b-601e-71bd-b3b6-dee3c668a9dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_019ef00b-601e-70e9-915d-27b09ff00c94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_019ef00b-601e-70e9-915d-27b09ff00c94" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019ef00b-601e-7c02-8a8f-38bd2124cfd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_019ef00b-601e-7c02-8a8f-38bd2124cfd0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019ef00b-601e-7448-9bfe-64f2c57d7798" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_019ef00b-601e-7448-9bfe-64f2c57d7798" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019ef00b-601e-7538-af97-bf72a647dbe2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_019ef00b-601e-7730-8db1-ce861c76beaf" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_019ef00b-601e-7538-af97-bf72a647dbe2" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/EarningsPerShareScheduleofComputationofBasicandDilutedEarningsPerShareDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#EarningsPerShareScheduleofComputationofBasicandDilutedEarningsPerShareDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/EarningsPerShareScheduleofComputationofBasicandDilutedEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019ef00b-601e-7a11-a0bd-e18413d4ef90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019ef00b-601e-7b21-a7ea-d894744ae6d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019ef00b-601e-7a11-a0bd-e18413d4ef90" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019ef00b-601e-7b21-a7ea-d894744ae6d3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019ef00b-601e-706f-bdb7-59f8b923adc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019ef00b-601e-7a11-a0bd-e18413d4ef90" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_019ef00b-601e-706f-bdb7-59f8b923adc0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://powersint.com/role/RelatedPartyTransactionsScheduleofAnnualMinimumRequirementsDetails" xlink:type="simple" xlink:href="psix-20260630.xsd#RelatedPartyTransactionsScheduleofAnnualMinimumRequirementsDetails"/>
  <link:calculationLink xlink:role="http://powersint.com/role/RelatedPartyTransactionsScheduleofAnnualMinimumRequirementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligation_019ef00b-601e-72e7-81eb-190f49092c2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligation"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInThirdYear_019ef00b-601e-7bc0-8cdc-e321b72479d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInThirdYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019ef00b-601e-72e7-81eb-190f49092c2c" xlink:to="loc_us-gaap_PurchaseObligationDueInThirdYear_019ef00b-601e-7bc0-8cdc-e321b72479d4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInSecondYear_019ef00b-601e-7b07-9c37-75204fb8ce1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInSecondYear"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019ef00b-601e-72e7-81eb-190f49092c2c" xlink:to="loc_us-gaap_PurchaseObligationDueInSecondYear_019ef00b-601e-7b07-9c37-75204fb8ce1a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_019ef00b-601e-77a6-9082-975d904b9759" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationDueInNextTwelveMonths"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019ef00b-601e-72e7-81eb-190f49092c2c" xlink:to="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_019ef00b-601e-77a6-9082-975d904b9759" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_019ef00b-601e-713f-bfa4-76c623d6f291" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PurchaseObligation_019ef00b-601e-72e7-81eb-190f49092c2c" xlink:to="loc_us-gaap_PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear_019ef00b-601e-713f-bfa4-76c623d6f291" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
