Musings on the fuel of saten
Ethanol (EtOH) is traditionally obtained from corn or palm oil because it's a low-cost source of sugar. That sugar can be converted to ethanol at the large volumes needed for commercial fuel. The chemical composition of ethanol is C2H5OH and is no different from the alcohol one might drink during a happy hour at your local watering hole.
The first possible down side is to sell ethanol as a fuel, it must be denatured so that you CAN’T drink it. Denaturing of EtOH is typically done by blending it with a small portion of petrol 5 or 10%, we already see E10 on the forecourt and we know it’s: approximately 10 percent ethanol, and the remaining 90 percent is petrol.
E85 (as used by many race series) on the other hand is a blend of approximately 85 percent ethanol and 15 percent petrol. The petrol is added to improve cold starting, which can be difficult at 100 percent pure levels; it also adds to the energy density of the blend.
So why are we bitching about it if racers are using the stuff at 85% with great success surely a 10% addition must be OK in everyday use ??
Well, the benefits of ethanol relative to race fuel are many fold, but the obvious one is power. A typical (R+M)/2 octane rating of E85 is around 100. This naturally high octane allows for greater compression and expansion ratios, (but you need them).
Secondly, ethanol has a higher heat of vaporization relative to petrol a typical heat of vaporization for petrol is in the order of 59 kilojoules per kilogram of fuel. For ethanol, it's approximately 130 kilojoules per kilogram, more than twice the value for petrol however it has a lower energy content.
Ethanol runs a lot cooler but you need to bump up compression to get it ignited and run far richer and burn way more ethanol than you would decent petrol fine in a race motor where fuel cost is generally not an issue.
Ethanol contains about one-third less energy than petrol. So, vehicles will typically go 3% to 4% fewer miles per gallon on E10 and 4% to 5% fewer on E15, 15 to 30% fewer MPG with E85 than on pump petrol a serious issue for most I would guess
And then there is the fact that ethanol is incredibly hydroscopic, metal fuel tanks are going to rust internally if left with fuel in for any time, it’s also a far better solvent than petrol meaning older vehicles or in fact any vehicle with poor quality rubber O-rings / gaskets / fuel hoses / carb float bowls or composite fuel tank will suffer as the fixtures and fittings start to melt
