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Engine Ignition Timing

Bill-93XJ

NAXJA Forum User
Location
Gotha, FL
Hey fellas, my knowledge of the electonics on the engine controls is pretty weak. If I wanted to tweak the ignition timing (advance it) a degree or two, how would I do that on my 93 Country? Slot the CPS holes and rock the unit to one side? I was toying with the idea of tryin the mod on MADXJ where the guy adjusts the MAP sensor to control the mixture. The plan is to lean it out a little and then if it pings to advance the timing a degree or two. Whatcha think?? Do-able?? Anybody done this type of tweak?

TIA........... Bill-93XJ
 
Matthew Currie said:
If it pings you'll have to retard the timing, not advance it.

i agree, you advance it until it pings and retard 2 to 3 degrees, at least this is how i time my harly.
 
You can slot the bolt holes in the CPS to advance or retard the base timing, but it cannot be adjusted beyond that because it's programmed into the engine computer.
 
If you choose to pursue this, you have to make the slots very precise, because the clearance between the tip of the CPS and the nubs on the flywheel (flex plate) is only a few thousandths of an inch. If it gets too close, it'll self-destruct, and if it gets too far away it won't generate any signal.

You're free to try this, but I don't recommend it. Jeep sold a high-altitude CPS with advanced timing for the non-HO models, and discontinued it when the HO came out because the ECU was programmed to do all the adjusting necessary. The ECU is also programmed to provide the optimum air-fuel mix, so in essence what you want to do is set up your engine to use a less than optimum fuel mix, the try to compensate by running less than optimum timing.

Somehow this does not seem like a great idea.
 
Amplifying what Eagle says, I note that my 95 is always on the verge of knocking when it isn't already knocking, and others have complained of the same thing. I doubt there would be much latitude for a timing advance even if the mixture remained the same, and none at all if you leaned it out. One of the reasons it was possible to offer a high-altitude CPS on the pre-91 models is that they have a knock sensor which retards the timing as needed. It also had EGR, which helps control knock. An 87-90 4.0 would make a better platform for timing experiments. My 87 never knocked no matter how dirty the engine was, or what kind of low-priced piss was in the tank. Hmmm...I wouldn't mind a source for some of that cheap Georgia gas right about now.
 
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