Gasoline is known as an aliphatic hydrocarbon and is made up of molecules composed of nothing but hydrogen and carbon arranged in chains. Gasoline molecules have from seven to 11 carbons in each chain. Gasoline is made from crude oil. The crude oil pumped out of the ground is a black liquid called petroleum. This liquid contains hydrocarbons, and the carbon atoms in crude oil link together in chains of different lengths.
Octane is a fuel's ability to resist detonation and/or preignition. Octane is rated in Research Octane Numbers, (RON); Motor Octane Numbers, (MON); and Pump Octane Numbers (R+M/2). Pump Octane Numbers are what you see on the yellow decal at gas stations, representing the average of the fuel's MON and RON. VP uses MON because this test method more accurately simulates racing conditions. The conditions under which fuels are tested using the RON method are not as demanding, thus the number is normally higher than the MON rating. This leads many other fuel companies to rate their fuels using the RON in an effort to make them appear more resistant to detonation. Don't be fooled by high RON numbers or an average -- MONs are the most relevant ratings for a racing application. Be aware, however, the ability of fuel to resist detonation is a function of more than just octane.
This is the speed at which fuel releases its energy. At high RPMs, there is very little time (real time - not crank rotation) for fuel to release its energy. Peak cylinder pressure should occur around 20° ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure (which is what the rear wheels see).
An expression of the potential energy in the fuel. The energy value is measured in BTUs per pound, not per gallon. The difference is important. The air:fuel ratio is expressed in weight, not volume. Generally speaking, fuels that measure high BTUs per pound have a higher energy value. This higher energy value will have a positive impact on horsepower at any compression ratio or engine speed.
The cooling effect on fuel is related to the heat of vaporization. The higher a fuel's heat of vaporization, the better its ability to cool the intake mixture. A better cooling effect can generate some horsepower gains in 4-stroke engines, and even bigger gains in 2-stroke engines.
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