Mods: If this belongs in another forum, my apologies, I figured it should go in the LT1 forum.

Okay, car was on the dyno recently:



I think I have at least 5-10rwhp more by leaning the A/F out to around 13.0 or so.

Here are three graphs...

First is a reproduction that is slightly enhanced version of the A/F vs RPM Graph.


This is the PE vs RPM table. (Power Enrichment) This is the % of fuel that is added or removed under PE mode (flooring it) depending on RPM


This is the PE vs Temp table. This is the % of fuel that is added or removed depending on temperature.


I've never done these kind of changes but I am sure someone here has. I'm just not sure how much to change the PE vs RPM table for a given amount of A/F points. Say I need to add 0.8 A/F across the board, anybody got any suggestions as to what that translates to in %?

Also, I have access to a Wideband O2 sensor, but I haven't put the O2S bung into my exhaust yet to test it with. I also have Datamaster on my laptop and can do logging. Can anyone with experience give me a little guidance?

EDIT: By the way, the current tune was done by Ion Soltan (MADZ28) some months ago and is an OBD1 conversion PCM. The BIN file was downloaded with TunerCats.

 

I just remembered to add that my Long Term Fuel Trims both hover around the 115-117 range. They're never farther than 1 digit apart, which is good. I just wasn't sure of the possibility of having a small header leak making me run too rich. But < 128 is taking out fuel, isn't it?

 

Honestly - unless you're after "just a number" on the dyno, I'd say it's pretty dang close. 13:1 on the dyno will give good numbers, but when you hit the street, it'll be lean (the dyno AFR actually leans out some once you start truly loading the car on the street). So your AFR on the street would be closer to 12.5: or 12.6: right now. If you're going to try to tweak it further, I'd shoot for 12.5:1 or so on the dyno. That should yield about 13:1 on the street.

As for "how much" to change... you'll just have to play with that.

Now, as for the LTrims. 115-117 with no split is good, in my book. As long as you're not hitting 108, and you're staying below 128, that's the zone of where you want to be.

Below 128 is the PCM pulling out fuel, but it's a good thing for WOT fueling. When you go to WOT, if your LTrims are below 128, they will jump to 128, and give you consistent AFR every time. If your LTrims are above 128, and you go to WOT, your fueling will be based on whatever LTrim setting you have. This gets worse if you have a split... For example, 125 Left 140 Right. At WOT, your left side gets fueled as an LTrim of 128, your right side as a 140. You'd see different injector pulsewidths and different O2 readings in this case... one side of the motor is getting more fuel than the other.

 

Well like I said, I'm just after a few more HP but I don't want just a dyno number. I have access to a wideband so I can always make sure I'm right at 13.0 driving around, I just have no idea of how much these numbers in the PCM change the A/F ratio.