You might also be surprised to know that fast burning fuels may not need as much timing as their slower burning counterparts. Many times we get calls from individuals who are dialing in their new motor on a fast burning fuel but they’re using timing and jetting numbers that worked on their old motor and fuel combo.
“Retard the timing a couple degrees and see what happens” is not the suggestion they expect to hear! With high octane, fast burning fuels, it is easy to dial in too much timing. In such cases, the engine is not detonating, but it is past the point of optimum spark advance. A little less timing may really wake up the motor.
OK, so we’ve got the high winding naturally aspirated big blocks covered – what about those turbocharged, supercharged, and nitrous-fed motors? Won’t the same fuel work for them too? Isn’t it the best? Well, yes and no…
Motors with lots of nitrous or boost don’t have to rely on fast burning fuels because the combustion chamber turbulence and pressure contributes greatly to the speed of combustion. This is even more true for smaller and more efficient combustion chambers.
For these engines, “heavier” fuels – those with higher specific gravity values – are usually better suited. Heavier hydrocarbon components in race fuels are very adept at holding off
combustion until the spark plug says “bang”.
Interestingly, heavier hydrocarbons may nothave the highest octane numbers, so be sure to consult with your fuel supplier for a good fuel recommendation. In all likelihood you will be looking at fuels with specific gravity values of 0.72 and higher.
Before we wrap things up here, do yourself a favor: when selecting a race fuel, look beyond octane. Sure, octane is important.
But if you want an edge on the guy in the other lane, consider the composition of the fuel too. With a little homework – and a little luck – you’ll be coming back for the next round. 
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