Underdrive Pulleys Installed - Dyno'd Before/After

[fdjizm]

The first run, oil temp was probably still colder. I've seen cars dyno slightly rich, the second run perfect, third run perfect, fourth run perfect, etc.

It looks like the first run was 12.3-12.4, and the second run was 12.6-12.7. That's only going to account for 3-4 RWHP. So if he gained 10 altogether (to make it easy), you can say he picked up 6-7RWHP from the UDP's. Something along those lines.

We could lean it out about 1% total, and maybe see another 3-4RWHP maximum. I'm happy with 12.7 if he is. (unless this wasn't before the cats, and it was taken from the tailpipe, then I'd like to pull out maybe 2-3% instead of 1%)

Usually how much is the difference between the a/f read from behind the cats? I did a recent dyno pull and my a/f were from 12.39 to 13.39 from the tailpipe on all three, so is before the cat (actual?) a/f leaner or richer than that? btw your tune was on point

 

[AMChrisRose]

Usually how much is the difference between the a/f read from behind the cats? I did a recent dyno pull and my a/f were from 12.39 to 13.39 from the tailpipe on all three, so is before the cat (actual?) a/f leaner or richer than that? btw your tune was on point

Thanks Bud, we did alot of testing in order to make our VCT, spark, MAF and drive-by-wire calibrations repeatable!

Since you have aftermarket cats, I expect it to be about .25 more on the rich side of things. If you're seeing 13, I expect it to be closer to 12.75, etc.

Stock cats, reading from the rear o2, I've seen about .5-.7 difference using 4 widebands and trying this on a few different cars.

 

[fdjizm]

Good to know that, thanks bro!

 

[AMChrisRose]

Not a problem!