|
|
|
        |
The last number the racer needs to know is the specific gravity of the fuel. This is important for tuning purposes. Specific gravity is very critical to your tuning. The specific gravity is essentially a measure of the weight of the fuel. Specific gravity is measured against the weight of water, which is arbitrarily assigned the weight of one. So, if you have a specific gravity of gasoline of .72, it would weigh approximately 72. "The ideal air/fuel ratio for spark ignition engines is generally quoted as being 14:1. Therefore, you need 14 pounds air for every pound of gasoline that enters the combustion process, through the carburetor or fuel injector system. "You need to know the weight of the fuel so you can adjust to the proper air/fuel ratio. Keep in mind that, normally, people tune to between 12:1 and 13:1 air/fuel ratio. You want to be more to the rich side of the storchiometric 14:6:1. "Most fuels will weigh somewhat differently one from the other. This is again where the consistency of the products is very important. If one week the competition uses a fuel that has a gravity of .75 and the next week he uses the same octane fuel, but it has a gravity of .73 that can significantly change the tuning setup. It may cause him to run differently with not as much power as he did the previous week. If you are racing at two tracks and buy fuel at each track, you may have bought two different products. You must be aware that the specific gravity of each product may be different. Always check the manufacturer's brochure for the gasoline's specifications and adjust your tuning accordingly. To be honest, most Saturday night racers can run a fairly wide range of specific gravity gasolines.The secret for maximum performance is to tune the engine exactly for the specific gravity of the fuel you are using each night. |
