Re: Knock sensors

[Glen Powell/SMC <Glen.Powell@smc.com>]

AHA! I think you may have hit on the technical difference/relationship between 
preignition and detonation. Preignition is when spontaneous combustion takes 
place prior to firing the plug, due to cylinder/head/piston hostspots, too high 
compression ratio and/or too high mixture temp. Detonation can result from 
preignition -or- from the plug firing when the pistion is too far away from TDC 
and/or compression is too high and/or mixture temp is too high. Closed-loop 
knock detection ignition systems can only prevent detonation due to firing the 
plug too soon, they cannot prevent preignition. However, the boost control 
system on the newer Audis *can* help to stop/reduce preignition due to too high 
compression and/or mixture temps by reducing boost pressure via CPU control of 
the WG. So, while ur-Qs cannot control either of these conditions, the 
knock-sensing systems with boost control can control both.

-bob