TurboTommy

This 30% more fuel thing keeps popping up.

By my math you need 50% more fuel using e85.

Another words, if you need "x" amount of fuel for a certain hp on gasoline; you'll need 1.5x amount of fuel with that same air flow on e85. So that's another half the amount of fuel on top of what you had with gas. Where I come from, that's 50% more fuel (50% of the original amount added on top).

Rogue_Ant

I asked a friend (Chemistry Prof) to explain the discrepancy to me, as my math agreed with you. His explanation confirmed that the actual increase in fuel requirement was ~30%. I am not a chemistry guy, so I can't really re-iterate what he said, but I do have plenty of customer's vehicles running E85 (including my own) and can tell you first-hand what is required...

Bri Bro

If you look at this chart, you are correct that 100% ethanol take 1.5 gallons to generate the same amount of heat (BTUs) as gas. E85 is better, but it still is 1.39.
http://alternativefuels.about.com/od...rces/a/gge.htm

E85 burns more efficiently and cleaner then gas in an engine. It also carries it own oxygen atom in it molecule so it has a lower AFR. A test that was done on a small engine, under controlled lab conditions, using E0, E10 and E85 at the ME department at University of Michigan-Dearborn and yielded the following results.

Energy Consumption, liter/kW-hr
E0= 0.598
E10= 0.609
E85= 0.77

Ratio of E85 to E0 = 0.77/0.598= 1.287
There is the number your looking for, it took 29% more E85 to make the same amount of power as gas.

That number changes with the blend and the blend changes with the seasons. The winter blend go to like 70/30.

TurboTommy

It's possible that it only takes ca. 30% more e85 to make the same power as gas; although I think it's a stretch and that would be comparing the two when running lean (probably for fuel economy purposes).
But, we're not interested in running lean. We want to maximize power (and safety) and we need to know how much bigger the injectors need to be, or how much bigger the pump needs to be, or how we need to program our engine management vs fuel pressure, etc.
And that folks, is 50% more fuel delivery on top of the original amount we had with straight gasoline.

stoich air/fuel with gas = 14.65
stoich air/fuel with e85 = 9.9
14.65/9.9 = 1.48

max power gas = 12.2
max power e85 = about 8.0
12.2/8 = 1.53

The only discrepancies I can see would be if e85 is actually less than 85% ethanol most of the time.
Also ethanol weighs a hair more than gas (and blends are calculated by volume), but this is a very small variable.

95ONE

You go ahead and put 50% more in.. Have fun.

TurboTommy

I have to admit I feel like I'm missing something.
But, one would think you would be at least curious as to the logic presented here. Instead you post something useless.

95ONE

I was curious before I converted. Not curious for years now. It presented it's own facts through experience. You're blatantly ignoring the ones that have experience and are trying to explain it to you. Please listen.

Laust Pedersen

It looks to me that both TT and Brian have good numbers, but answer different questions.

Brian’s number answers the question: “How much more E85 (volume) is needed to generate the same power as when gasoline is used?”

TT’s number answers the question: “How much more E85 than gasoline is needed, if the engine is ingesting the same amount of oxygen for the two cases?”

As I see it, the latter would be relevant only if fuels stays liquid until the (intake) valve is closed. So if that is the case the extra oxygen in the liquid E85 explains the 29% vs. 53% difference. That again would have the implication that E85 could generate 153/129 = 19% more power.

Laust

gruhsy

Are we talking E85 Energy by volume or weight difference? They give different values. Might explain why people are getting conflicted values.

TurboTommy

Some of yous are over thinking this and making it more complicated than it is. Disecting this into the chemistry realm is not neccessary because the bottom line has been established; and that is the stoich values of the two fuels. There happens to be a factor of about 1.5 between them, which represents the difference in fuel flow; cut and dry. Like I said earlier, e85 is a bit denser, so this number might be a bit less, but it's gonna be close, especially at max power.
It's probably true that only 30% more e85 is needed at cruise conditions due to the more tolerable flammability limits, but this is not relevant to us when we have to engineer our fuel systems for our cars.

Bri Bro

My car spends 90% of the time on the track with around 30% more fuel for E85 at a lambda of around 0.8. As stated before, the ratio does change so you have to go up and down on the ratio during the year.

I think there are two of use (on this post) using E85 and we have the same values for the ratio. Several vendor that support E85 also have the chips setup for this range. If you setup for 50% more I don't even think the car would start and it certainly wouldn't run well.

95ONE

Tommy, not that I want to say anything more than a neutral tone here. But I think You are over thinking. I'm not talking about cruise. I'm talking about 100% full load throttle differences. I tuned race gas, then I tuned E-85. Average was right at 30% more. There are always variances up and down the whole map, but the average was 30%


Exactly....

NZ951

Thats an extremely small turbo for a 3.0. I had the #8 housing on a 60-1 turbo, on my 2.5, changed it to a Garrett .61 and had a massive pick up in power through the whole rev range. A 3.0 should really be looking at using a Garrett GT3582 at a minimum with a .82 turbine housing and looking to make 500WHP+ at the wheels, all day long. A friend has a 4AGE 1.6 that runs a Garrett GT30 turbo with a .63 housing and he makes 533WHP, to put it into perspective.

NZ951

PS, I ran 98 octane on my track car (4AGE 1.6 N/A build), and made 169WHP, then tried Aviation Fuel which is over 100 Octane, and it made 175WHP, we are planning an E85 tune at some point, I am expecting another 10 or so HP, through ignition advance. The only thing that puts me off is having to drain it after race meets.

333pg333

There's just too much actual evidence of guys running around the ~30% extra with E85 to ignore.