I just learned the other day that the Delphi system has used variable ignition timing which reads "spark knock" via plugs and wires. It's called something like ion spark ignition; I used to be a Benz tech, and Benz used the same system. I never did get a clear explanation of exactly how this worked, despite asking about it during technical training at the Mercedes Benz training center (Benz seems to treat some tech info like top secret info, even from their tech instructors and dealer technicians), but what I gather is that the system somehow measures the current required to fire the plugs in order to determine whether or not detonation or preignition is occuring and adjusts accordingly. I assume that all of these systems operate on the same principle (which of course, I don't fully understand; what I just stated is the extent of my sketchy understanding based on the vague explanations I got from the instructors as well as what I surmised). This is why I asked about the plugs being compatible. I did not know the HD engine management system had this capability until I was talking with someone about dyno tuning my bike the other day. If anyone out there knows more about this function in the HD fuel management system and has a clear understanding I would love to hear it.

I just about had my mind made up to get rid of the stock ECM in favor of S&S's VFI system, in lage part because of the variable igniton timing afforded by the knock sensor. However, it was pointed out to me that because of the nature of knock sensors, other things could cause it to pick up false readings, including a loose primary chain slapping around in the primary case as well as some other factors. This shouldn't be an issue for me since I have the automatic primary chain adjuster, but nevertheless it seems that the stock system is more sophisticated than I thought it was, and since it has adjustable ignition timing via the ion sensing ignition this seems like an invalid reason to replace it with something else. This guy pretty much sold me on using the TTS (without giving me a hard sales pitch), though for now I'm going to stick with my Power Commander for budget reasons. But either way the stock ECM retains the ion sensing system, provided the correct (or compatible) plugs are used.

Can anyone shed more light on this ion sensing ignition system and either confirm or correct what I think I know?

 

My dyno tuner told me the same thing. If you change plugs or wires from the stock ones the ion sensing won't work. I can't explain how or why but That's why I stayed with the stock plugs.