chriswtx

iTrader: (5)

Went to the track last night. And it was very hot and humid. Just in the hour when the sun started going down and the temperature droped 10 degs, we both picked up 3mph. I have just installed a wideband oxygen sensor and my car goes way rich in 3rd and 4th gear. The air/fuel ratio drops into the high 11's(11.7/11.8). I also had some spark knock in those gears. So either I am running rich in those gears or what I think is really happening is that under the higher load of 3rd and 4th I was getting spark knock and the computer was pulling timing and adding fuel to correct it. What do you think is causing this rich condition? In 1st and 2nd gear my air/fuel is right on at 12.7 and 12.8.
Opnions please...

Mods are Vararam, Z06 sways, B&B's cat back

dvanorder

What tuning have you done? Vettes are PE tuned rich out of the factory, especially the higher RPM's where they sit around 11.8 for a safety cushion. Plenty of room to bring that table down after getting the rest in line. I put my car on the dyno with a decent VE tune and an untouched PE table. It almost followed the PE table perfectly----12.2 working it's way down to 11.8 between 4400 and 6000. With AFR that rich doubt you were knocking due to detonation; other factors likely at work.

chriswtx

iTrader: (5)

The only thing is that in 1st and 2nd gear up to 6000rpm the air/fuel is fine at 12.7. Its only when it gets into 3rd/4th gear that it goes rich to 11.8. It still has stock tuning. I will get it tuned as soon as I get the headers installed. Its just weird that the mixture is fine in 1st/2nd gears and not in 3rd/4th gears..

Robert56

iTrader: (2)

Not sure what the PE multipliers are on a C5, but had a similar issue on my Z06 with Vararam, sounds like a tune is in order. My stock Pe is set for about 12.3 upto 12.6 at 3200rpm, then down to 11.9 at 5200rpm, then back upto 12.1 the rest of the way. However, because the Vararam causes a lean condition and ltft's go positive to compansate, then, the postive fuel trims freeze where they are at when positive and add themselves to your wot enrichement. I was seeing 10's for my wot. I re-tuned ltft's and VE and recalibrated maf and know a/f at wot is dead nuts on to the facory settings. However, I have modified them since for a dry shot. hope this helps to get some insight into your issue.