Originally Posted by
mxatunerjg
I've tested this in the past, but thinking about this now I don't think I was testing things in the way you are talking about. I believe what I was trying to do was find a way to get a target fueling at idle of say 13.9-14.1 AFR for engines with a cam that had a lot of valve overlap. It has been probably 2 years since trying all of that, and I'm betting that at the time I was probably thinking about what my widebands were reading, not so much what the computer was doing at the time. I remember setting stoich to something in the range of .075 FA, primarily because at the time Diablo had told me that I could do what I was attempting by changing the stoich value. I do remember noticing that no matter what the stoich value was, the trims still targeted a Lambda value of 1 or approx 14.7.
I do understand the o2 sensors switching at 1.0 Lambda, that is normal. I also understand the PE being an adder to the stoich value for the target PE fueling. My guess would be when I saw the change in fuel trims I was focused on trying to change a fueling target for closed loop and it didn't work. Over time my memory of that testing probably got foggy and I changed my thinking to be that the stoich value was nothing more than a value used for the base adder for PE fueling.
So if all your saying is true, then I believe if an injector setup was dialed in on a vehicle running say 93 octane, and a switch to e85 was made, changing the stoich value should put the fueling very close to where it needs to be. Meaning, if the injector scaling and fuel tuning was correct on 93, that should all stay pretty consistent when making the switch if the stoich value was changed in the ecu. Example....A car is dialed in to a perfect 0% trim on 93 octane, and let's say the difference between 93 octane and e85 is exactly 30% fuel required, a 30% increase in the stoich value should net a 0% trim, and PE fueling should be very close as well?