A mini spring car’s fuel is usually fed through fuel injection which you will also know as constant flow that uses mechanical fuel pumping in order to decrease and increase the fuel flow directly to the unit that relates to the rpm. Using this method you or your team can change the fuel amount that is fed to cylinder quickly when you change the by-pass-jet or pill to a larger jet size which will cause the fuel amount received by the engine to lessen while more returns to the fuel tank.
If you want the mixture to be richer your jet size gets smaller and for leaner mixtures you use a larger jet. In the same light do I have to add that fuel pressure also directly relates to the speed of the engine, thus should you look at getting a high speed jet in order to ensure the released fuel to the tank is at the pressure you want it set to. Generally an electronic fuel injection system is not permitted in mini sprint car racing according to their standards.
The fuel allowed for mini sprint cars includes only gas pumped, racing gas or methanol. Methanol though is the preferred fuel for mini sprint cars for numerous reasons aside from the speed. The safety factor when you use methanol is the main reason though why it is recommended as it is much less volatile than when you use traditional gasoline or petrol as you know it too, as flash fire and explosion risks are significantly reduced. Then also for engine cooling, you probably know that methanol burns at a much cooler rate than gasoline.
Talking about ignitions, your car’s spark is via a magneto system and that is for a car that does not use a battery, but a car that burns alcohol. Mallory and MSD are two of the main manufacturers of ignition systems for all sprint cars and you could get one from them or a similar manufacturer.