Quote Originally Posted by kriskyk View Post
Ahh interesting I just assumed that stoic was the same or very similar for most gas and didn't change until you got into ethanol or some other exotic fuels....
The simple work around to this is to tune by lambda instead of air/fuel ratio (AFR), which is what any tuner even remotely worth his/her salt is going to do because there is simply no way to know exactly what mix of fuel is in the tank. The stoich AFR value for gasoline is 14.7; for E10 (which is what nearly all pump gas in the US is) it is closer to 14.1. The stoich lambda value for both is 1.

Oxygen sensors are lambda sensors - always have been, always will be. The numbers people are more familiar with seeing take that lambda value and multiply it by 14.7, assuming they were using gasoline. It's been many years since you've been able to reliably find ethanol-free gas - I've usually only seen it around marinas due to the known issues with using ethanol in a high moisture content environment.

Bottom line: tuning in lambda gets you around this nonsense. You still need to find what WOT lambda value gives you the best power/torque for your application. If you are having a vehicle tuned, pick the gas you intend to run most of the time and tune to it. It's that simple.