E85 in our cars?
Reply #15 –
Remember, Octane has little (if anything) to do with how much energy fuel holds. Octane is a measure of how SLOW the fuel burns. The higher the octane the slower the burn, which means it is more resistant to detonation. Faster burning fuel can explode, causing detonation, which can actually split engines in two if done right :D
The only way a person will get more power out of higher octane fuel is if they have forced induction and/or a knock sensor. A knock sensor will allow the engine to run more timing advance, thus increasing power. Force fed engines can produce more power with higher octane through higher boost and more timing.
Any engine that does not have high copmression, a knock sensor or forced induction (in other words, every stock V8 or V6 fox 'Bird or Cat, or even any stock HO upgraded one) will not benefit from high octane fuel. At all. It won't produce more power. It won't idle better. It won't burn cleaner. It won't run smoother. It won't blow flowers out the tailpipe. You will receive ZERO benefits. If you fill with supreme and claim to notice a difference it's either because your car has a mechanical problem that the higher octane is helping to hide (timing too far advanced, combustion chambers carboned up, inoperative EGR system) or you have an active imagination that's trying to convince you you're not wasting your money.
The oil companies will benefit, though, watching many people throw their money away for nothing.
David is correct about the energy content though - E85 contains significantly less energy density than straight gas. Less energy density means that for a given energy rerquirement (such as steady state cruising) you will have to burn more fuel to achieve the same thing. You will get fewer miles out of a tank of gas. The only way you can compensate for the lost energy is to make the engine more efficient at using that energy, such as raising the compression ratio, increasing timing or turbocharging the engine to take advantage of that higher octane.
I seem to remember the original Mach III concept was calibrated for E85 and produced very impressive numbers for it...
I agree with your octane rant, though nobody was making any claims about the higher octane, David simply stated that E85 was higher. :D
I inject ethanol/methanol (& water) mixture to help cool my charged air and the increased detonation resistance of the combined mixture is a nice side benefit as well (mostly due to the water though since the heated vaporized ethanol/methanol may actually lower octane if what I read is true.) In a supercharged application, there are many benefits as you stated (cooling, oxygen in the fuel, detonation resistace).
Topic: E85 in our cars? (Read 1766 times)
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