muncie21

iTrader: (14)

I've had my new LS6 heads on for about a week now. SOTP, can't really tell the difference between them and the LS1 heads. Took the car out on a long stretch of highway and let'er loose....now my AFRs were running in the single digits during PE. Like 7's and 9's. Never did this before with the old LS1 heads. I can't believe just installing a set of heads could do this.

So here's where my head (no pun intended) is at. Pretty sure my fuel system hasn't gotten 50% better in the last week. Since I'm not putting more fuel into the engine, I'm thinking that my heads aren't flowing as much air as they should. Any ideas what would cause this? Low and part throttle driving seem pretty normal. It's just when I go WOT that the AFRs are wacky. BTW, the tune hasn't changed, nor has anything induction related.

Ideas?
I'm going to post this in the LS1 Engine section, to get the perspectives from the gear heads. I'm thinking it's something mechanical...like bent pushrods, etc.

Black02SS

iTrader: (36)

How are you measuring your AFR? What wideband and when is the last time it was calibration properly.

SSpdDmon

iTrader: (10)

My first guess was COT protection....I know that dumped in extra fuel on mine, but never down in the 9's. Did you tune your car or someone else?

muncie21

iTrader: (14)

Here's a couple pics of my run. First pic is SD mode. O2 are switching fine, then when I go into PE, AFRs drop about 2 points below commanded. Clikc to view larger image.

[IMG][/IMG]

Here's a scan of my return trip. I re-enabled my MAF to see what it would do. Big mistake!! Didn't see the lean AFRs during PE until I got home and looked at the log. Looks like when the MAF takes over (~4K RPM) it's telling the PCM there's more air going into the motor than there actually is.
[IMG][/IMG]

This tune (with stock heads) ran fine on the dyno about 4 weeks ago. I'm thinking something has changed regarding my high RPM airflow (alot less air flowing than there should be), but can't put my finger on exactly what it could be.

muncie21

iTrader: (14)

Any ideas guys? I'm running low myself.

SSpdDmon

iTrader: (10)

I wonder how accurate your WBO2 readings are??? It's very odd to see it go from single digits to 15~20AFR on the return trip. Did you change the tune before heading back? What have you done to your tune overall? Why are there +3.8% trims during WOT in the first picture?

Those are the questions running through my head. If you can't answer them I'd do two things.

1) Triple check the wiring and accuracy of the wideband: In other words, recalibrate the heater as well as do an open air calibration while the sensor is warmed up. Then, reprogram it to output a range of 2V to 2V. After that, log with your scanner the raw voltage reading coming from the wideband. It should be within +/-.002V. This is how you check for voltage variations in the grounds. If everything falls in line with the wideband, log the calculated AFR. For 2V, the scanner should read ~13.35AFR. This is how you check your equation in the scanner for the LC1 [AFR=(V*3)+7.35].

2) If everything with the WBO2 looks good, the only other thing I'd suggest is to restore your stock tune and start over.

muncie21

iTrader: (14)

I did a free air calibration when I got back. The WB checks out fine.

The reason the return trip is different, is because I re-enabled MAF for the return.

I re-flashed with a couple of tunes that dyno'd fine (AFR wise) and still the commanded vs. actual is off. I don't know how, but I'm thinking that somehow I'm flowing less air up top than I was before....