Batman & Mach...Preparing for S/C

[SLOWBRAEATER]

It seems like the 3.4 gets much better results than the 3.8 with the msd dis4. I recall someone saying they tested the dis4 on a 3.8 and it didnt make a bit of difference, i also remember some people saying the 3.8 has a sufficient ignition system as it is.

[nocutt]

<blockquote>quote:</font><hr>Originally posted by SLOWBRAEATER:
It seems like the 3.4 gets much better results than the 3.8 with the msd dis4. I recall someone saying they tested the dis4 on a 3.8 and it didnt make a bit of difference, i also remember some people saying the 3.8 has a sufficient ignition system as it is.<hr></blockquote>

I concor!! I do not know how the 3.4s are setup, although I do know many fiero owners employ aftermarket igntion boxes when using the F-bod 3.4s. So that makes me think the ignition system can easily be overtasked especially when FI is added to the picture.

Arctc Wolf,
I cannot speak for the 3.4 but in principle it is better to retard timing when FI is added unto an engine that didn't employ this mod before. On the 3800S2, I noticed when I run the car without boost...I have no KR (remembering that we have this module stock) even with 1psi of boost, if I do not remove spark timing or better put delay spark timing I will get KR. I remember running as much as 100 octane and 5 psi of boost...O2 were about .093-.096 @ WOT! Guess what? I was getting as much as 14 degrees of KR and then this will drop significantly when there was less load on the engine say about 4800-5600RPMs, @ 5700RPMs I was seeing about 7 degree of KR! When I started tunning out KR, I simply retarded timing 2 degrees for every pound of boost. The car changed in performance...The PCM was giving me as much as 26 degrees of timing advance @ full throttle with 7psi of boost. Now for those who don't understand, that is a lot even for the street...and even @ 11 psi I was still getting as much as 22 degree of timing advance...Thank goodness for 100 octane! My point? Retarding timing in this scenario is only telling the PCM to delay an event that hasn't happened yet, with FI you are filling the Cyl at a very fast rate. Igniting the mixtures sooner than optimal leads to colliding flame fronts...so a delay is needed. And fortunately for the 3800S2, the knock sensors can "see" the problem before you hear it...misfires is a secondary issue compared to retarding timing for optimal combustion!

[ June 13, 2003: Message edited by: nocutt ]</p>