Here’s a crystal-clear look at engine knock and pre-ignition in a beautifully done digital animation.

This jewel of a video—courtesy of Niterra, maker of NGK spark plugs—provides a rare and useful glimpse of two events in engines that we usually never get to see and sometimes only hear: knock and pre-ignition. Knock is pretty much a fact in modern internal combustion engines, since they’re designed to run in incipient knock aka silent knock. That is, the specs and calibrations are chosen to run the engines right up to the edge of significant knock to squeeze out the last bit of power and efficiency.

While the two terms are easy to confuse, knock (also known as detonation) and pre-ignition are two different phenomena, but this digital animation clearly illustrates the difference, and also how the two are causally related. There are more terms in circulation related to knock these days including super knock and low-speed pre-ignition (LSPI), but with the knowledge in this video, those terms can easily be understood as well.

Along with the useful theory, the video also provides some valuable info for hands-on mechanics, for an improperly installed spark plug can induce pre-ignition by altering its heat range. If the plug is under-torqued, its gasket or conical seat can’t fully transfer heat into the cylinder head, obviously. But when a plug is over-torqued the metal shell can be slightly distorted, repositioning the porcelain in the shell and inhibiting its ability to transfer heat. This is all good stuff to know, and the accompanying text is brief and gets right to the point. Video below.