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Race Gas:

Force Fed offers a variety of race gas based on your cars demands.

Brand of Fuel Research Octane Motor Octane Specific Gravity

F&L “Xtreme 100” 105 96 .74

F&L “SP-3” 118 109 .725

VP “SB-3” 103 99 .743

VP “C16” 117 .735

Understanding The Properties & Octane Ratings of Race Gas

Below we will attempt to help you better understand how race fuel works by explaining to 4 basic qualities of fuels. As in everything, there are trade-offs. You can't make a racing fuel that has the best of everything, but you can produce one that will give your engine the most power. This is why there are different fuels for different applications. The key to getting the best racing gasoline is not necessarily buying the fuel with the highest octane, but getting one that is best suited for your engine.

1. OCTANE: This does nothing more than rate a fuel's ability to resist detonation and/or preignition. Octane is rated in several different ways: 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. Many fuel companies rate their fuels using the RON in an effort to make them appear more resistant to detonation, so it is important that when comparing fuels to make sure that you are comparing the same method of rating. 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.

2. BURNING SPEED: 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).

3. ENERGY VALUE: 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. Fuels with higher BTU’s will have higher energy value, this has a positive impact on horsepower at any compression ratio or engine speed.

4. COOLING EFFECT: 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.

OCTANE NUMBERS AND WHAT THEY REPRESENT

A commonly asked technical question is: What is the difference between Motor, Research and R+M/2 Octane Numbers. Another frequently asked question is why some fuel companies represent their fuels with Motor Octane Numbers, while other companies use Research or R+M/2 Octane Numbers.

To answer these questions, we need to first explain the machines that do the testing. These machines were made in the 1930s and were designed to test for octane ratings between 0 to100, any number above 100 is an extrapolation. These machines are dinosaurs & are not adequate for today's high tech fuels or engines, but they the only means available for testing fuels. These machines are one-cylinder engines that have an adjustable head that can move up or down to increase or lower the compression ratio while the engine is running. The Motor and Research machines are the same in this respect, but they differ in several other characteristics. The following is a comparison of the two machines used for testing octane numbers:

	Motor Machine	Research Machine
RPM	900	600
Intake Air Temp.	300 DEGREES F	120 DEGREES F
Timing	VARIABLE BASIC SETTING 26 DEGREES	FIXED AT 13 DEGREES (DOES NOT CHANGE)

As the comparison above shows, the Motor Octane machine runs at a higher RPM, hotter temperature and more timing. This machine will put more stress on any fuel and more accurately represents a racing engine. Since most people reading this are primarily interested in fuels for racing applications then it is best to look at the Motor Octane. The Research Octane machine will always produce a higher number for the obvious reason that it does not put the same amount of stress on the fuel. The R+M/2 Octane Number is the average of the Research and Motor Octane numbers and is the number displayed with yellow labels on retail level gas pumps.

When comparing fuels for racing purposes make sure to compare Motor Octane Numbers because these are the ones that count when racing.

NOTE: Definition of “Specific Gravity”: The specific gravity of a substance is a comparison of its density to that of water.

With that being said the following is true. Fuels with a higher specific gravity number have a higher resistance to detonation because they fall down the cylinder faster. The faster the fuel falls the quicker the fuel gets away from largest concentration of heat (top of the cylinder or combustion chamber). Cold is denser than hot air so it falls where hot air rises.