Running a bit lean on WOT pull
 

Anyone have any ideas why I'm running a bit lean on WOT pulls? I always seem to be running ~.50 or sometimes more leaner than the command AFR on a WOT pull everything else looks good as far as fuel trims. I know I'm getting a little bit of knock but that is primarily attributed to the fact that I seem to be running leaner instead of richer.

I recently just switched to the stock exhaust manifold & I used new gaskets (used GS gaskets for the header to block). I double checked my torques when I did the re-install. Made the O2 sensors snug.

Mods: K&N Filter, Catback Exhaust, OFT Stg 1 91Oct Tune

Here are a few pulls...

http://datazap.me/u/phantobe/stg1pul...=0&data=1-5-10 3rd Gear

http://datazap.me/u/phantobe/stg1pul...=0&data=1-5-10 2nd gear

http://datazap.me/u/phantobe/stg1pul...=0&data=1-5-10 I think 3rd gear again

http://datazap.me/u/phantobe/stg1kre...5?log=0&data=1 Daily Driving

I was gonna get under the car this weekend to check things out...but any ideas or suggestions to troubleshoot this?

This guy ^ also ended up having a similar AFR to me @zeppy

Change in manifold could do that, if it's not a physical issue then just add some fuel in.

What's your O2 scaling like?

I haven't touched any of the scaling just using the OFT Stg 1 91 octane tune. Only I think I did was pull a bit of timing to compensate for knock.

Not really sure why the ECU isn't adding fuel. Like under WOT until about 5k LTFT is 0% while the AFR is not that close to the command AFR.

use the vgi utility to touch up the maf scaling mainly the open loop, but wont hurt to do both.

I guess I'll give it a try, is it okay to do OL scaling before CL scaling?

normally you do CL first then OL

although your CL looks ok

Gotcha...

Is it okay to do 2nd gear pulls for data? Or is 3rd gear preferred (the guide recommends 3rd or 4th), I don't have a lot of stretches of road for 3rd lol.

:cheers:

Did you reflash after swapping manifolds? The trims could still be learning after the swap.

Yep. Ran stg 2 uel when I had uel header in. Swapped to stock. Flashed to factory, ran for a bit. Then flashed to stg 1.

In open loop the commanded and "actual" AFR can be and usually are different. Nothing says they should match up. Either scale the WOT portion of the MAF, which will throw load and therefore ignition timing out, or just make the Open Loop fuel table richer by the same percent that the AFR is "off".

I understand they will be different and they won't be exact however in most/all cases I've seen the AFR generally richer than the commanded AFR. My case the opposite is true, which seems to be much rarer.

I'm going to do the OL MAF scaling and see if that fixes the issue. I still think I'm going to get under there and remove the skid pan and make sure everything looks good this weekend. However since I'm running lean @ WOT would it more likely be a fuel or vacuum leak? Or could it be either.

Thanks for the help gents

Here's my OL MAF Scaling...

http://i.imgur.com/V0Md7rD.jpg

@steve99

It looks like it's either 1. a hardware/sensor issue - in which case you should screw with the tune until it's sorted, or 2. It's a Stg1 MAF scale running on Stg2 tune - that's the only time I've seen oft run so lean.

I scaled the ol maf and it looks much better, initial impressions. I'll post some logs tomorrow.

I'll double check the tune tomorrow but I think if I'd know very quickly if I was running a stg2 tune on a stock exhaust manifold. I'd imagine you'd get tons of knock occurrences.

If you look at the op that was the only other person I saw with a similar issue.