Originally Posted by Savington
Jason, J_Man mentioned you guys are going to try a non-OEM wheel to make the OEM cam sensor work - is that just for fun or does full advance on the VVT make the sensors lose sync?
The 96+ crank sensor wheel won't make the AEM lose sync over the VVT range.
My interest was a higher resolution crank trigger wheel. The AEM cannot time off of all crank teeth if they are irregularly spaced - so it has to "throw away" 2 teeth and time off of 2. Some say that this lack of resolution can cause timing errors during transients, such as during rapid engine deceleration. During rapid engine deceleration in theory the next spark could be a bit too advanced because RPM is now significantly lower than the previous cycle.
This is probably worst at low RPM because the effective sampling is slowest. The one situation I can think of of low RPM rapid deceleration is when you abruptly get on the gas at low RPM and the drivetrain windup oscillates (you know, where the RPM goes boyoyoing, for lack of a better term
At higher RPMs and loads one detonation event may in theory cause a slight deceleration, and misfire would be the worst. I have seen arguments regarding this but not actual numbers (i.e. experimental results).
Regarding the AEM, the highest resolution crank trigger wheel it can handle is 12 teeth. Because of how the AEM syncs, and because the VVT range is 47*, the AEM needs to use a 12-1 trigger wheel to work with VVT. The missing tooth is so that the AEM can tell which of the 12 "teeth" is TDC. With such a wheel, the missing tooth needs to always fall between cam pulse edges regardless of VVT position.