What delta are you guys seeing between commanded and actual AFR?

[johnsZ06]

I tuned a car's WOT AFR the other day on a dynojet with wide band and I had to set the PE vs RPM to 11.8 to get 12.8 on the wideband. What are you guys seeing?

[dc_justin]

I tuned a car's WOT AFR the other day on a dynojet with wide band and I had to set the PE vs RPM to 11.8 to get 12.8 on the wideband. What are you guys seeing?

I command 12.8 to get 12.8.

What I think you will find is that most here will "fix" the underlying table(s) that cause a disparity in commanded vs actual, rather than modify the PE table to get it where you want it. With it that far off, (11.8 to get 12.8), then I can only assume that after a bit of driving, the trims are going to trend positive, which will likely carry over into PE mode and richen it up a bit more, bringing it closer to 11.8 when all is said and done...

Another thing to be aware of is if you're having to command more fuel to get your target, then everything will be off on the tune. Spark reference, torque calculation (for automatic transmission cars), etc.

[johnsZ06]

Well, the thing is I was kind of rushed to get the AFR within target because of limited pulls so I had to do what I had to do. The one thing that worried me was the car was getting around 8 degrees of KR which I couldn't explain unless it was bad gas. The car was using the basic spark map with about 22 degrees on top and was still pinging like crazy. The whole thing made me very tense but at least he won't detonate due to being lean.

I scanned the parameters of each pull and I couldn't see why he would be running any leaner vs. commanded. Of course, that's taking into consideration the wideband was working properly.

One thing I did note was the car had 122k miles on the clock and might of had a a lot of carbon buildup which might explain the KR.

[dc_justin]

Well, the thing is I was kind of rushed to get the AFR within target because of limited pulls so I had to do what I had to do. The one thing that worried me was the car was getting around 8 degrees of KR which I couldn't explain unless it was bad gas. The car was using the basic spark map with about 22 degrees on top and was still pinging like crazy. The whole thing made me very tense but at least he won't detonate due to being lean.

I scanned the parameters of each pull and I couldn't see why he would be running any leaner vs. commanded. Of course, that's taking into consideration the wideband was working properly.

One thing I did note was the car had 122k miles on the clock and might of had a a lot of carbon buildup which might explain the KR.

So on the spark map it showed about 22* up top or you saw about 22* in the EFILive scanner?

[johnsZ06]

I saw 22.5*.

[johnsZ06]

Here's the last pull. When I opened the tune tool it showed 24* commanded.

[SSpdDmon]

That to me looks like 30* commanded (22.5+7.5).

[johnsZ06]

That to me looks like 30* commanded (22.5+7.5).

I know what you are saying but when I opened up the tune tool it was showing 24. So I'm a little confused as well.

[dc_justin]

I know what you are saying but when I opened up the tune tool it was showing 24. So I'm a little confused as well.

What PID are you using to display airmass (g/cyl)?

[dfe1]

I see a few things that are potential problems. The knock is long and repetitive indicating low quality gas or an excessive amount of oil in the combustion chamber. With 122,000 miles the rings, valve seals or both may be passing a lot of oil. What was engine coolant temp during the dyno runs? If it was 190+, that could be a contributing factor. I assume the PLX wide band was not connected since it's showing 16.8:1. Have you checked to make sure you don't have some spark being added through one of the coolant temp adjust tables? As SSpdDmon has pointed out, something is calling for 30 degrees of spark.