Ethanol curious

**dethinboots** · 03-28-2013, 01:57 PM

I was wondering if E85 mixed with 93 would yield any gains while drag racing. It is alcohol and I get the thinking behind that. but would it be wasted on an untuned engine?

**goof4080** · 03-28-2013, 06:04 PM

Just like putting 100 octane race fuel in your tank...unless your computer knows to change the tune you will be wasting fuel and $$.

**dethinboots** · 03-28-2013, 06:27 PM

That makes sense. thank you

**Firebirdjones** · 08-06-2013, 05:11 AM

This is a few months old but important to point out a few things.

E85 is an alcohol based fuel, of which is 85%. It has a stoich of 9.7:1,,,,far different from the 14.7:1 stoich of regular gas. Simply putting E85 in the tank of a vehicle that isn't tuned properly for it would cause an extreme lean condition, doesn't matter if the car needed the octane or not, it would take itself apart.

Also works better in an engine that is built specifically for E85. Since it has a big cooling affect on the intake charge as well as better octane, you can run upwards of 13 to 14:1 compression on a naturally aspirated engine, and it's great for boosted engines as well allowing you to get more aggressive with boost and timing on a given combo.
Simply putting it in an engine that is designed to run on regular pump gas even when tuned for it (10:1 compression or less) the advantage is much less apparent.

For an engine tuned on regular pump gas, and you feel you need some extra octane or if you are chasing false knock issues and want to eliminate the fuel part of the equation, stick with regular racing fuels and avoid the alcohol based stuff.

**pajeff02** · 08-06-2013, 06:04 PM

^^ On the money.

Adding to what FBJ said, people commonly think that an engine will make more power if you dump a high octane race gas into the tank. Not true... as octane is really equated to resistance to pre-ignition (or knock), it requires more ignition lead to take advantage of its properties. Our cars actually have both high and low octane spark tables programmed into the PCM, but they do not take into account anything higher than the usual 91-93 octane premium fuel available at filling stations. So, just dump a high octane race gas into the tank and the end result will actually be less power as the peak cylinder pressure will arrive too late in the engine compression cycle due to the slower burn.