The tune is off. A 12:1 ratio is nearly a full point rich. I run around 12.7-12.8 at WOT and both of my cats are still the ceramic color (not black) after 2 years of driving.

Will you gain 30rwhp by leaning it out, no, but it will be better for the cats, fuel econ and power/tq will go up.

Another thing to keep in mind; my car uses a very short and direct intake. Not sure how the G8 is setup. The VE table is a good 2-3% different between on the road and on the dyno due to a ram air effect. So the road tuning may be spot on but on a dyno it could look off because the engine is getting a little less air.

The motor seems to be peaking a little early too. My cam isn't too far off from yours and peaks almost 1000RPM later

 

My intake is a Vararam over the radiator, so its pretty much a straight shot into the intake. And the fan they were using was on its 3rd set of last legs. It was barely moving any air. So, yeah definitely a difference in airflow. G8RAM has pretty much the same cam, and peaks right at the same RPM, of course on his he made 408 with landspeed heads and SLP catted longtubes. As far as the AFR, I think around 12.5 is where we wanted to be, which may have been the case when using the wideband on the road. Then again, it could have crept a little since that tune. Seems to happen a bit with the G8s ECM.

 

Something definitely not right with this result. Who installed the cam - was it degreed correctly?

I would expect at least 390rwhp on one of your dynos over there with that cam in an A6 L98 - even with short 1 3/4" primary 4-1 headers and cats like many run over here.

Good luck with it.

cheers

 

It was installed by a GM mechanic I met through the G8 forum. Unfortunately I wasn't able to be around during the install. I was having it done while my son was visiting from Virginia. That being said, I can't say for sure everything was 100% correct, but the guy isvery competent and does it for a living, so I will give him the benefit of the doubt that everything is installed correctly. There is really only one way to know for sure though.

 

Here is a pic of the G8 intake.

http://vararam.com/images_new/G8-in-car.jpg