Nearly Died Last Night!

Alter Ego Trip · June 22, 2015

There is a sensor to detect the ethanol ratio and it adjusts motor configuration / tuning accordingly. So, while you are correct in that lack of advanced timing on E85 won't produce a HP gain, you are wrong in the assumption that the motor is "tuned" just one way. It adapts to the fuel that it senses.

I stand corrected. Technology is a wonderful thing. So if that's the case, the truck should run differently on 91than 89 as well then I'd assume.

ember1205 · June 22, 2015

I stand corrected. Technology is a wonderful thing. So if that's the case, the truck should run differently on 91than 89 as well then I'd assume.

Octane is nothing but a measure of gasoline's resistance to detonation. High compression ratio motors (anything above about 10:1 in modern motors) could cause pre-detonation on the lower octane fuels (spark knock), and are spec'ed to require the higher octane fuels. If this motor's compression is that high, and has its timing adjusted to compensate, then I would fully expect there to be a difference in performance. I just don't know that this motor's compression is high enough to create an issue like that.

As far as the rest of it - the link detailing the dyno runs and such actually discusses the sensors and what-not, and even details some of the sensed alcohol levels of the fuel at and after changeover.

Alter Ego Trip · June 22, 2015

Octane is nothing but a measure of gasoline's resistance to detonation. High compression ratio motors (anything above about 10:1 in modern motors) could cause pre-detonation on the lower octane fuels (spark knock), and are spec'ed to require the higher octane fuels. If this motor's compression is that high, and has its timing adjusted to compensate, then I would fully expect there to be a difference in performance. I just don't know that this motor's compression is high enough to create an issue like that.

As far as the rest of it - the link detailing the dyno runs and such actually discusses the sensors and what-not, and even details some of the sensed alcohol levels of the fuel at and after changeover.

Thanks, I'm familar with octane and compression.

I didn't read through the whole article, I'll have to do that to see if 91 would be a benefit over 89.