Think about an 87 vs 93 tune. At WOT, both are using approx the same amount of injector, but the timing and boost amounts would be different. So, if you have an 87 tune (for example), the 93 wouldn't add anything, but if you're running a 93 tune and use 87, then hopefully the knock sensors will save you by retarding timing and boost. The ECU has both short and long term correction strategies to help with these things.
As far as a mix of ethanol it's more complicated, since besides timing and boost, the injector pulse width is also affected. So, if you're using say straight gasoline in an e50 tune, we can definitely assume you're going to be running lean. In this case, the o2 sensor is used as a correction strategy, as well as the knock sensors.
The actual answer is you have some leeway if you're just running down the highway in closed loop mode, but if you fill up a cold car with the wrong stuff and then go full WOT, it might not compensate in time.
I remember a post ZFG made on this very subject a while back, try searching his posts to find it- as I remember he said there was some leeway, but I don't remember any specifics.
As far as a mix of ethanol it's more complicated, since besides timing and boost, the injector pulse width is also affected. So, if you're using say straight gasoline in an e50 tune, we can definitely assume you're going to be running lean. In this case, the o2 sensor is used as a correction strategy, as well as the knock sensors.
The actual answer is you have some leeway if you're just running down the highway in closed loop mode, but if you fill up a cold car with the wrong stuff and then go full WOT, it might not compensate in time.
I remember a post ZFG made on this very subject a while back, try searching his posts to find it- as I remember he said there was some leeway, but I don't remember any specifics.
But the issue is also a lot more complex than you are giving it credit. For example on a 93 tune you can mix in up to 30% ethanol and be completely fine the truck can adapt fuel wise and it can also add timing. What you have to remember is these are not running ancient ecu's they have adaptive close the loop spark as well. On a 93 tune your typically going to see five to six degrees of timing, spike it with e30 and the truck is going to add timing on its own and with the freedom that it has in the 93 to and it's going to end up in the 10 to 11 degree range keep in mind it knows where and MBT timing is and can't go past it.
Even if you screwed up I put way too much ethanol in it it has a couple of safeties. If it hits 100% duty cycle with it will pull power rather than go lean. It's actually virtually impossible to make it go lean(with my tune) some tuners disable stuff they shouldn't. Today I actually had a customer that was intending on spiking their 93 tune and filled up 100% of e85. Tune did exactly as it should and pulled the power and let him actually drive it, he's burning the tank out to get back down to e30.
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