Before I put the LTs w/ catted Y on the car it put down 333/344 several pulls w/ about a 13.1-13.3 air/fuel ratio on the stock tune. I logged the runs with EFI live which my O2 sensors showed this to be about .872- .905 on the runs w/ some KR (1.7avg not exceding 2.5) to no KR on the .900 run.

After headers I never felt like it was really pulling that well. I had the MAFT set to 5% base which puts the LTFTs just slightly negative (-1 to -3 or so). I know I have this dialed in as best as possible with the MAFT.

I never really got WOT set well and it was only set to 2% lean which I figured the car was still running pretty rich.

I did a "street log" running from about 3000RPM up in 2nd gear (i guess this is a good measure) and found the O2s to be reading at about .925 at WOT. This seems to be quite a bit richer than where the stock tune had it before headers where it ran really strong.

First question is how rich is this? And how much would this affect power?
On the dyno the avg timing advance was 23 or so before and it is now at about 25 degrees avg.

I worked the MAFT up to a 8% lean setting (6% more than I was running) and the O2s are now at .900 with 0KR until 5000+ where it is only about .1 or so. I'm guessing this is a good safe place to stop?

Also would leaning the car out by 6% have a noticeable effect on power? Any idea if 6% on a MAFT would make a signifigant decrease in fuel?

The car feels quite a bit stronger now but my *** dyno has never been very good.

I'd appreciate any input you guys have.
(And before someone says you should go by LS1 Edit/ HP Tuners etc. I'm just trying to get the car dialed in better with what I already have).

Thanks

 

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I can't believe NO ONE has any ideas.

 

The car will work to learn out any MAFT changes. Its great for making quick changes on the dyno or at the track, but long term, the car learns it out. This is primarily because the MAFT never really knows what WOT is... it just has a airflow measurement above which it moves to the WOT scaler.

 

It "should" not learn out the WOT part but the base
settings, yeah, will get learned away. Thing is, headers
mess with things the MAFT doesn't touch or only has
partial authority over. Low-RPM airflow is only partially
MAF-derived, the headers really shift your volumetric
efficiency (VE) and the speed-density tune that rules
idle and low cruise, and drives the fuel trims that stick
with you into WOT if lean. That, and headers screw up
the O2s' operation quite often from thermals.

You would probably get more from a set of 'Vette rear
O2s up front than any MAFT foolery. If you're jacking
the MAF scaling around, to chase idle / cruise mixture
drift from headers, you're shooting ducks during wabbit
season.

 

From what i've found the MAFT doesn't learn the base setting....it stays consistent.

Thanks for the help. I'm sure I could use a good tune but I think it is running much better for now.