67King

FWIW, here is the derivation. It is based onoctane, rather than gasoline. I did it with gasoline, too, but for whatever reason, I didn't keep that notebook. Sorry I don't have time to retype it, but I've had this handy for a while. Bottom line is ethanol is only about 70% as efficient BY VOLUME as gasoline. But it can generate much more heat (energy, power, however you want to call it) for a given amount burned.

TurboTommy

Well, how do you guys know how much more fuel you're really running, for sure.
There's 3 things that dictate how much fuel is getting into the cylinders: injector size, fuel pressure, injector pulse width
Unless you were the one who programmed the software, how do you really know? At the end of the day, if your car is running great and your wideband displays the correct AFR, you're not thinking about it anymore.
When the topic comes up, the 30% thing just gets erroneously repeated.
But, you could be flowing more fuel than you think.

I've tried to present a logical argument, here; with hard numbers.
So, replying back with:
" well, me and the boys are all running 30% more fuel, so who are you, Tommy, to say we're wrong"
is not an explanation as to why I'm possibly missing something which would prove that it's actually 30%.

67King

I think that is the source of the disagreement. LBT with E85 is much closer to stoich. Also, LBT with gasoline is a range depending on application, not a hard number. Most turbos run much more rich than 12.0:1, usually 10-11:1 becausee of the hotter air charge (using the fuel to cool the air charge).

TurboTommy

Not really.
What your attempting to explain is the specific energy of the fuel.
E85 only has about 2-3% more specific energy than gasoline. Another words, if you changed nothing else other than switching to e85 (no increase in timing, boost, CR, etc) you would gain 2-3% horsepower from a chemical energy input point of view.

Anyway, none of this even matters.
Let's say your airflow is 40lb/min.
Stoich you would need 2.73 lb/min of gasoline,
and roughly 4lb/min of e85
How is that only 30% more fuel?

TurboTommy

Again, totally irrelevant.
Folks here are running the same chemical richness (lamda value) with e85 as they would with gas. Maybe even richer.
Therefore the fuel components have to be in place to provide for the extra flow.

67King

I was attempting no such thing. What I was doing was explaining the loss of fuel economy people experienced when they ran E85 in the flex fuel vehicles. Chemical equation to determine molar quantity of fuels consumed with a fixed amount of oxygen (air). From there, how much energy that fuel was capable of producing, and adjusting the consumption accordingly. Then finally accounting for the differences in densities to show the difference in fuel economy as measured in MPG's. People complained that their fuel economy was reduced by about 30%. I calculated 32.6%. With gasoline, rather than octane, the number was lower.

Is it perfect? No, but it is what goes on. With FFV's, you don't adjust boost or CR or anything but fuel. The difference here is that we can take advantage of the octane equivalency to increase the boost levels. And while there is a 6.4% increase in potential due to the heating value of the fuel (again, octane, becasue I had it, gasoline will be slightly lower), it is often not realized becasue the E85 displaces 4 times as much air as octane, which reduces volumetric efficiency.