In closed loop operation i can agree with the car running very close to stoich but once you are full throttle, there is no reason to be close to maintaining perfect fuel economy. I'd be more suspect to say that the 02 sensor was bum or installed incorrectly.

Jermaine~

 

The car is bone stock and i only had it for a month. could it really be the o2 sensor?

 

Mmmmmmm...shouldn't be.
My overall guess is: 1) the tailpipe sniffer naturally shows the A/F readings slightly lean, 2) you might not have the best gas (91 octane or less, or not a good tank of gas) 3) your car is very slightly biased to run on the lean side. Not sure what else.

 

Not your stock 02, the dyno facilities 02 sensor is in question here.

I had a guy recently call me to tell me about how he wasn't sure that his personal wideband wasn't tuned well. So he proceeds to tell me how his dyno facilities wideband said he was running at 14.0 to 1 under boost and his personal wideband which happen to be our own product said he was running about 11.5 to 1. He made above 500whp with his personal wideband reading about 11.5 to 1 but when he tuned it based on shops wideband he was down to low 400whp.

These tools are very sensitive and should be installed correctly to achieve the correct afr. It's common for use to stop using the tailpipe sniffer when we feel the afr and other supporting data do not correlate with, idc's, fuel pressure and so on.

Jermaine~

 

If there car is never run hard... and these were his first dynos I'm very inclined to say his car will be running lean. We've seen it on the Dynojet!!!!

If the ECU has not adjusted for the need of more fuel, it won't use it.

 

So...if I've driven my car pretty hard for several tanks of gas, then I drive it like a grandma for 1/2- 1 full tank of gas, would the ECU revert to a grandma setting? I'm beginning to dislike the ECU if this is true.

 

Not even a tank of gas... just a few minutes.

The engine is going to head in the direction of your driving habits. How many pulls on the dyno did you make to give us these figures?

 

besides.. he's running stock. 13-14 isn't all that lean. This isn't a FI install looking for an AFR of 11 to help cool the cylinders or anything.

I don't see the 'fear' here.