General Help Tuning?

[steveo]

I've heard that 12.5:1 is usually ideal for making power

that totally depends.

max power on many engines is closer to 13:1, and some engines like more fuel in some regions, that's why dyno tuning results in best power gain rather than widebanders simply trying to hit a particular AFR.

also despite the base fuel map being close, intended target is often different from actual achieved target... even if you get all your trims perfect, power enrichment might still not be what you expect.

a major mfr like gm usually aims for somewhere between 11:1 and 12:1 on stock calibrations to prolong engine life during abuse at the expense of a minimal power loss, and also as a safety threshold to keep the engine alive in event of mechanical problem, sensor inaccuracy, inconsistent fuel quality, engine production differences, etc.

[90Vette]

That makes sense, thanks. Without access to a dyno or a WB O2, what AFR in PE would you suggest I aim for?

[steveo]

i'd suggest 12:1 but matter of opinion. you can slowly remove a bit of fuel later and see if the effect is positive.

[90Vette]

First off, I'm ecstatic to say my car just passed smog with flying colors! I'm not sure how much having a new cat played into that, but I was surprised that with a bigger cam and homebrewed tune I passed so easily. Thank you to everyone that helped me!

Now that it's smogged, I have a driveability issue to work out - once hot, the engine randomly dies - but after that I'll be right back to playing with PE. I think I'll add in 2-3° of PE timing and drop the PE AFR to 11.75:1 to start, then slowly work my way up in AFR and down in timing until I find the sweet spot. Does that sound good?

[steveo]

you need to figure out if it's spark or fuel or both you're losing. there's a good chance the ICM is flunky

[90Vette]

Actually, ICM is at the top of my list! Glad you confirmed that.
I also am considering the ignition switch, but the cut-outs seem to correlate more with a long run-time than with bumpy roads.

Do you have any preferred replacements? I'm considering replacing the coil too if I can find one that doesn't hit on my hood.

[Eds]

I had a similar problem. The dielectric grease dried out and the ICM would over heat. I cleaned things up, re-installed the ICM with new grease and the problem went away.