Why am I running rich during PE?

[SSpdDmon]

If you're still seeing large swings after installing the MAF screen, my next step would be to make sure the MAF is thoroughly clean (can get MAF cleaner at Autozone type stores) and maybe try "clocking" it if there's room to do so. Depending on the path of the airflow, you may get better readings if the bar in the middle of the MAF is verticle instead of horizontal (or vice versa). Give those sugesstions a shot before throwing money/parts at it.

[joecar]

Yes, try those things, clock the MAF position, and with the screen redo the MAF table.

Also try the stock duct to see if it makes any difference, try it with and without the screen.

[n8dogg]

Ok I'll clean and clock it. What do you mean redo the MAF table?

[joecar]

With the MAF clocked/screened, redo the BEN correction on the MAF table B5001...

i.e. anything that changes how the MAF reads will require the MAF table B5001 to be corrected again.

[n8dogg]

Something weird is going on. Almost like something in the tune itself that's hidden. I played around last night with the tune by adding 2% to the MAF calibration and the AFR is identical at WOT. I then took the MAF back by adding -2%. Took it to work this morning and my LTFTs are averaged at -3.5%, AFR is the same at WOT (11.6-12.0). I did reset fuel trims a few nights ago and it's hot and humid outside. Would resetting fuel trims and hot and humid air have a negative effect on my tune? Do I need to do more work now that my fuel trims are off or do I need more seat time to allow the fuel trims to adjust after being reset?

[SSpdDmon]

Is there a chance catalytic overtemp protection is still enabled?

You will see some swings in FTs as weather conditions change. So, I wouldn't be too concerned about a 2~3% swing.

Please list all mods and post up a copy of your current & factory stock tune. I'll take a look and see if anything stands out.

[n8dogg]

It's disabled, just checked. I did a search on the corvette forum and people are saying to turn fuel trims off and that they are applied during PE. So are they MAF only OL PE mode? Or are trims applied? If trims were applied I think I'd run lean wouldn't I? I'll have to find wifi on lunch and upload the logs from last night and this morning.

[joecar]

OL: trims are not applied.

CL: last positive trims are applied in PE mode (on top of PE table).

When trims are applied in PE mode, they will never remove fuel, they will add only.

Yes, post logs and tune file.


More info: Summary-Notes -> post #4

[n8dogg]

Thanks guys, I will get my logs and tune up asap. I will read more through the summary notes when I am not on the clock .

Here is a reply I got on the Corvette Forum, what do you guys think?

just cause you set your PE@ 13.0 or whatever doesnt mean it w ill do that. Not until you actually tune the MAF table.

when you go WOT your LTFT a STFT are not being used any more. You have to adjust your HZ to make your afr correct. so do a WOT run
put 1.129 in your PE table.
log WOT

if at 8600HZ you are 12.3 the take the 8600 hz cell and multiply by aprox .94 that should get it really close to the 13.0 you are commanding

[Mr. P.]

...Stoich at 14.68:1...

You sure that you're running 100% gasoline?? It is common here for stations to water down their gasoline with 5-15% ethanol; also due to Obama EPA laws, ALL pump fuel in the US will be at least 10% ethanol (E10) by 2012, so I would just change the stoich value to 14.17 now IMO. Either way, make sure the fuel you are using matches the stoich value in your tune.

Mr. P.