E85 Tuning And Prep

Sh0velMan

It is true that there is less BTU per gallon in E85 than gasoline and requires much more of it to burn in a stoich mixture.

MPG is irrelevant due to that fact and the fact we're talking about power, not "miles per gallon", which is not the same as engine efficiency. One reason diesels get better 'MPG' is because diesel oil is much higher in BTU content than gasoline. As a general (read: not 100% true) rule of thumb, the heavier the petrochemical, the more BTU is locked up in it. Ethanol is much lower viscosity and specific gravity than gasoline, therefore you need more of it to get the same amount of work done.

That said, it is 105 octane from the pump and has a much lower combustion temperature.

Forced induction cars can see upwards of 20% gains simply be re-tuning on E85. N/A cars can see gains too depending on the setup and specifics.

I'm planning on re-tuning for E85 as soon as I get a fuel cell. Our cars aggressively modify ignition timing based upon fuel quality and coolant temp. Bumping to 105 octane while reducing combustion temps is a win-win.

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SouthArk370Z

Thanks for the info.

While it is true that hydrocarbons (LPG/gasoline) follow the "denser = more energy" rule - Ethane, Methane, Propane, Butane, Gasoline are increasingly denser and have more BTU - EtOH is not a hydrocarbon. EtOH, while having less energy content (21.2 MJ/L vs 34.8 for gaso and 38.6 for diesel), is more dense (0.79 g/cm3 vs 0.71–0.77 for gasoline).

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Sh0velMan

I guess you're right on the density being higher of ethanol (an alcohol) than gasoline (a composite of several compounds lacking the relatively large amounts of oxygen present in ethanol).

So yeah, for hydrocarbons, heavier is more, not necessarily true for other compounds.

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