It makes you faster because of weight savings.....in your wallet
One of the best things about race fuel is that it is a consistent grade. I had some real issues in Calgary in the 2010 nationals when I got bad pump fuel.
From a horsepower perspective it is important to try to avoid ethanol enriched gasolines if possible, even if they are higher 'octane'. Ethanol doesn't enriched gas, it actually degrades it.
Alcohols have much lower stored energy, which can be measured in British Thermal Units (BTUs), than gasoline. When alcohols are added to gasoline the resulting product has less stored energy; meaning more throttle (fuel) is required for the same horsepower/speed (also producing lower fuel mileage numbers).
From a horsepower perspective it is important to try to avoid ethanol enriched gasolines if possible, even if they are higher 'octane'. Ethanol doesn't enriched gas, it actually degrades it.
Alcohols have much lower stored energy, which can be measured in British Thermal Units (BTUs), than gasoline. When alcohols are added to gasoline the resulting product has less stored energy; meaning more throttle (fuel) is required for the same horsepower/speed (also producing lower fuel mileage numbers).
Specifically, ethanol has an energy content of about 76,330 BTU per US gallon (3.78 litre) and regular gasolines have about 114,000 British Thermal Units per US gallon (3.78 litre) depending on brand and formulation etc. A blend of 10% ethanol (E10) will result in a gallon of the mixed fuel having 110,230 BTUs, or a 3.3% decrease in stored energy compared with the pure gasoline component.
The scenario is worse for higher octane blends; premium gasoline has approximately 125,000 BTUs/gallon, and after blending with 10% ethanol produces a mixed fuel with 120,133 BTUs/gallon, or a decrease of 3.9%. Obviously, the performance reduction gets worse for blends using 15% ethanol (E15).
Darel
This is pretty one sided and misleading IMO.
Sure if nothing is changed in the engine and what controls it, an ethanol based fuel may make less. Buuut..... (big but) if the engine and fuel system are optimized properly then the ethanol based fuel can make more horsepower...
The fuel supply volume would have to be increased and the timing advanced, but it most definitely will not make less power if this is done. The higher octane rating of the ethanol allows for more advanced timing (due to better knock protection), and there is more oxygen in ethanol than gasoline. With the extra oxygen in the ethanol, it has a lower stoich compared to gasoline. With that it has to be run richer than gasoline (more supply), but running the extra volume makes it more than compensate for the lower energy per unit per volume in the end.
So yeah it 'makes' less energy per unit of volume, but the ability to use more of it makes the output higher (and that's not even including the benefit of being able to use extra timing).
That being said... I wouldn't tune a bike on the ragged edge for a pump based ethanol or alcohol based fuel. Strictly for the fact that pump fuels and their ethanol content would not be consistent enough for my liking. But if it was a controlled fuel from a reliable source, I wouldn't hesitate to setup a bike to run it.