Rogue_Ant

Yes, the energy density is lower, but not by as much as most think. Gasoline is 114000BTU/gallon. E85 is 81800BTU/gallon. However for the same amount of air, ~33% more E85 is used. So the reality is that E85 is ~108800BTU for the same amount of air as needed for one gallon of gasoline. That is less then 5% difference in BTU between Gas and E85.
Further, in rich conditions, E85 does not drop off in power nearly as bad as gas. Gasoline max power rich is ~12.5, but E85 is ~10.5. As most turbo cars are tuning for high 11s, for safety, E85 does not suffer nearly the same amount of loss as gasoline.
Additionally, as E85 is injected it cools the intake charge much more than Gasoline does, resulting in a denser mixture. This means more power and safety, beyond what the 105octain rating implies.

-Rogue

TurboTommy

With my calculations, I got about 48% more fuel needed at stoichiometric, with e85.
So the specific energy (the actual energy released at proper air/fuel ratios) is about 3% higher than with regular gasoline, depending on the BTU value that's listed with various pieces of literature. This is at stoich. As mixtures richen up from there, alcohols tend to increase power slightly more than gasoline. Power will continue to increase with richer mixtures than gas, but then timing needs to be advanced to take advantage of this. There's no reason why you couldn't realize a 10% power increase just with tuning (at the same boost as with gasoline).
I'd say this is pretty good to those who wondered what the fuel alone would be good for.
Achieving density increase might not be a big part of the equation because I don't know if most of the fuel has a chance to vaporize before the intake valve closes. Probably, the biggest advantage of the cooling ability of the e85 is the in-cylinder cooling, increasing the threshold of detonation at higher power levels.

Rogue_Ant

Um, care to elaborate on your calculations...?

TurboTommy

stoich for gas is around 14.65/1
stoich for e85 (85% ethanol, 15% gasoline) is around 9.85/1
then calculate from there
or, where did I go wrong?

gcb951

So with a piggyback like I have (SMT-6 with Vitesse), what would my max A/R be at WOT? Right now I get between 12.0 and 11.5 with WOT. Bases on what has been said in this thread I should be around 3% greater than that right? BTW what would 3% more be after 11.5 on wideband?

Rogue_Ant

Well, you said that it needs 48% more fuel, that would put the stoich AFR at ~7.64:1 - obviously not correct.

Take:

1 - (E85 stoich / Gas stoich)

That results in ~33.5%.

-Rogue

toddk911

True, but cured by dropping in some ethanol STA-BIL. It fights the water attracted by the ethanol.

And as Rogue pointed out, there are numerous benefits that, for me, would greatly out weigh any negative aspects.

Its like being able to run on race gas all the time for very cheap, plus a cooling effect on the charge air like Rogue mentioned, which would possibly raise the 105 to about 110, give or take. So even with no boost increase, which would be silly , the amount of gains from timing advance and cooler/denser charge alone would be significant across the board.

Its pretty simple, E85 is 85% ethanol which is bascially denatured alchohol made so that we can't drink it; so E85 is like running on 85% alchohol.

JDS968

Good info! Learn something new every day...

While we're on the subject...regarding this:Would there be a similar potential for a little extra power gain naturally aspirated, by reprogramming the ECU for more spark advance? Or is it only relevant under boost? This would be with water/methanol injection, rather than race gas or E85.

racerxrick

this was great as is tyhe rest of the thread!

Thanks!!

TurboTommy

Hmmm;
we must have different definitions of what 48% more fuel is.
We know that one has to flow more with e85, so we are looking for a higher number. Therefore we have to divide the gas stoich by the e85 stoich
We seem to be in agreement on the stoich values of e85 and gas. So that being said, for a given amount of air ingested into an engine you will need "x" amount of gasoline. When you switch to e85, you will now need 48% of "x" added on top of "x".
If somebody tells you they ate 50% more cookies than you, and you ate 12 cookies; show of hands, who would think: "okay, they ate 18 cookies"
By your definition, you're going to be assuming they ate 24 cookies.

toddk911

Gains are far more for boost, but plenty of gains can still be had in any motor with more advanced timing; be it from e85, meth/water inj. etc.

I'm sure we have all seen Horespower tv and seen them go from a base timing tune and then after a few timing advances, they pick up 10-15% on an NA motor; 6-10 degrees can make a big difference. Then you add in the cooling effects of e85/meth inj. and even more can be had due to the denser charge air. The butt dyno proves that one. Drive your car on a 95 degree day and then with no changes drive it on a 45 degree day.

JDS968

Now I'm even more tempted to do it soon...

Good point, never even thought of that!

Car? Try flying a Cessna in those conditions!

ehall

mmmmm....cookies....