E85 vs. Gasoline HP comparison
 

...here's something from 2010 GM for those die-hards (me?) who argue that using E85 always reduces HP output:

http://archives.media.gm.com/us/powe..._HHR_Combo.pdf

Its not that it reduces power so much as the fact that it has much lower energy content and therefore cannot go as far as 1 gallon of E10 or E0

from what I understand if you do the math the end result is your losing money if you use e85 however its better flash point and can be used in high compression engines draw back is generally lost h.p.

Alcohol is used in drag cars alot with superchargers, it makes a huge difference in power because of the heating and increased pressure the forced induction creates, the cooler burning fuel works much better.

For normal cars, the advantage is really that E85 burns cleaner,
and is made in the USA. I see it locally at $3/gal, E10 is $4/gal,
so the price is a wash really, just like diesel fuel is ~25% higher and gets ~25% better mileage..

What would be really good is to run on Natural Gas, as the price has plummeted while oil has skyrocketed, it has become 4-7 times less expensive than gasoline. Been thinking to build a car that uses NG.

The problem is that you can build an engine to be optimal with E85 or you can build it to be optimal on gasoline. When you have to go back and forth is when you lose in both areas. EFI tuning can take up a lot of slack in both areas, but some of the basic differences are cam timing, compression ratio and injector sizes.

^ Yup. If an engine is built to run E85 only, and not E0 or E10, it will have higher compression and advanced timing, and therefore be more efficient at extracting energy from the fuel, leading to only a small mpg drop compared to an engine tuned optimally for gas.

...from the 2011 EPA Fuel Economy website:

2011 HHR FFV M5 2.4L/4 22/30 GAS
2011 HHR FFV M5 2.4L/4 16/23 E85

...thats a 17% FE reduction in city-FE and a 13% reduction in highway-FE values.

That's because the engine cannot change it's compression ratio to take advantage of the higher octane fuel.

...I was just emphasizing the fact that although HP might not decline with E85-vs.-gasoline, the Fuel Economy certainly does.

...that is, unless (as you correctly state) the engine can actually "use" the higher octane value of E85, such as is possible with turbocharged engines...ie: they're "designed" to run on E85 and gasoline.

...and, just having a turbocharger is NOT enough, there must also be both wide-range sensors and programming capable of handling both gasoline (E0) and gasohol (E85).

^ Agreed. Ideally, an engine should be set up for one or the other, not both. However, the best we can do to handle both well is a moderate compression engine with plenty of boost. Pull some timing and cut the boost bigtime on gas, and crank it back up on E85, being continuously variable for a mixture of the 2.

I'm really not sure why there's even any discussion on the topic, the differences between ethanol (or E85) and gasoline aren't that hard to understand.

E85 has fewer BTU's per pound than straight gasoline, so more fuel mass is burned per work unit created. Nobody argues this. It's apples/oranges, because "number of BTU's in a pound" is not a useful indicator of worth for an automotive fuel.

E85 brings drastically more oxygen to the combustion chamber than gasoline, which serves to effectively improve the volumetric efficiency of the engine. Why? Because less air has to be pulled through the intake tract for a given BTU output, and as a secondary result less inert atmospheric gases have to be shoved through the engine and exhaust system for a given BTU output. This also means that for a given throttle position, considerably more fuel is being dumped into the engine. This brings total fuel BTU content per combustion back in line with gasoline (if not greater than), so net horsepower should almost always be greater on E85 than on gasoline in the same engine, assuming the engine's control systems are capable of dumping the requisite amount of fuel in.

:thumbup: