Knock con­trol of mod­ern en­gines

Car (South Africa) - - TECH -

Knock sen­sors are ac­celerom­e­ters mounted on the block of an en­gine to “lis­ten” for the on­set of knock (or auto-ig­ni­tion). If de­tected, the ECU re­tards the ig­ni­tion tim­ing to pro­tect the en­gine, im­pact­ing per­for­mance. Most mod­ern en­gines are cal­i­brated to run on 95 un­leaded petrol to pro­duce the claimed max­i­mum power out­puts and will re­tard the tim­ing only when a lower-oc­tane fuel is used. There are, how­ever, ad­vanced knock-con­trol sys­tems able to ad­vance the tim­ing un­til the on­set of knock. The re­sult is a higher power out­put than claimed at the stan­dard of 95 oc­tane.

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