DISTILLATION

Gasoline is made from many different hydrocarbons that boil at different temperatures. This process is called distillation. The boiling temperatures are generally reported for the initial boiling point, 10%, 50%, 90% and the end boiling point. These numbers tell you how a gasoline will perform. The Reid Vapor Pressure RVP impacts the temperature of the initial boil and 10% points. A gasoline with low 10% and 50% boil points can improve performance considerably under some conditions, but you can run the risk of vapor lock.

When a racer uses a gasoline with a very low initial boiling point, the fuel volatilizes easier. They are using a mechanical fuel pump with 10 to 15 feet of fuel line, it can vapor lock because the gas is volatile, especially in warm operating conditions. We have not gotten into the exotic stuff because we want our customers to use a fuel they can be satisfied with all the time. They don’t have to look at the air temperature and heat on the track to decide if they can afford to use some trick fuel that weekend or not.

The racer needs to be careful about getting a gasoline that is too volatile, especially if they are using a mechanical fuel pump running off the engine sucks the fuel through 12 feet of fuel line. That process pulls the gas molecules apart, adding to the vaporization of the gasoline. If you run an electric fuel pump mounted at the rear of the car, you are pushing the fuel through a pressurized line. It is not as the likely to vaporize the gasoline in the fuel line. Never run the fuel line by the exhaust system. It will only heat up the gas and cause it to vaporize before it gets to the carburetor.

A difference of five degrees does not matter. Take a look at the 50% point. It is 220 degrees at the 50% point. There are some gasolines with 170 degrees at the 50% point. Those are the ones where people will have problems. The trick of the week can help you win a race this week and lose the next. If the gas vapor locks on them, they are not going to have any power, and everybody will come around them.