Why am I running rich during PE?

[n8dogg]

After performing Calc.VET tuning (a few times) I feel I have an accurate VE table and the car runs very smooth. The only issue is my AFR at WOT is around 11.9-12.2 when I am asking for 12.5-12.7.

I know my MAF freq has always been a bit jumpy, especially at higher RPMs. BUT I have recently installed an airflow straightener from Halltech, didn't seem to help much.

Here is my latest log: 7.20.efi

My guess is the MAF is causing this since the PCM looks at MAF freq during WOT (right?).

Any help is appreciated. I'd really like to see what she does when it's running at optimal AFR.

[joecar]

Hi n8, I'll look at it tonite/tomorrow.

[Taz]

Post your tune if you are able ... will take a look for any additional enrichment in the tune itself - to rule out this possibility .... many eyes often find a solution.


Regards,
Taz

[n8dogg]

Thanks guys

Here is my current tune:Calc.VET_2.tun

[Taz]

Took a quick look at the tune ... nothing jumps out as being causal. No extraneous fuel adders that I could find. Stoich at 14.68:1, PE from 1.15 (12.75:1) to 1.17 (12.54:1). MAF has a smooth consistent curve, VE shape is also well done - some of the transitions could be smoothed a little more (but that's just the old man being picky !).

Also took a quick look at the log - WBO does jump around a fair bit (even when not in OL / PE). Hopefully Joecar's keen eye will spot something.


Regards,
Taz

[SSpdDmon]

MAF needs to be redone with the addition of a screen. It makes sense that it would be off by a larger delta at higher airflow. It's altering the path of air right in front of the sensor. I guess it's possible that the VE would need a touch up as well, but I doubt it.

[joecar]

Some background info:

we previously noted that the MAF has large swings at WOT as rpm increases (MAF waveform would jump down 60 g/s and then back up);

n8 had installed an aftermarket duct, we're not sure if this is causing the MAF swings;
n8 installed a honeycomb screen on the MAF to see if this makes any difference and it appears not;

we know the PCM is able to filter out some of the MAF waveform swings, but we're not sure how large a swing it can handle.

[n8dogg]

I do have the stock intake, I could install it and log to see if things smooth out.

[Taz]

Hello N8,

Haven't logged an OL MAF only tune in a while - these work well for certain applications - if memory serves I think that is what Jeff (SSpdDmon) is using in his Camaro. Truck tunes use B4206 (O2 trim in OL) by default. Corvettes do not. Can't recall if B4206 trims in OL only, or in OL and PE modes. Enabling B4206 may assist (if it trims in PE) with promoting safe AFR until you find a more permanent tuning solution.


Regards,
Taz

[n8dogg]

Halltech has a newer style intake kit that utilizes a card type MAF found in newer Corvettes. Do you think I would see a more accurate reading by retrofitting a card style MAF? It's too bad I'm a perfectionist otherwise I'd leave it be. Not sure how much power I'm really sacrificing. Do you think the 90+ ambient temp could cause any of this?