Wort des Tages
7 March 2026
knock
nounKfz-Technik
Preignition, a type of abnormal combustion occurring in spark ignition engines caused by self-ignition; also, the characteristic knocking sound associated with it.
Warum dieses Wort
Named straight from the sound, though the sound is not metal hitting metal: it is pressure waves from a second, uncontrolled flame front ringing through the block. Purists also split preignition from detonation, since one lights before the plug and the other after.
In use
It only knocks under load going uphill, so back the timing off and see if the knock clears before you go pulling the head.
Written by our editors to show how the term is used, not a recorded quotation.