The throttle is the primary input in determining how much fuel to deliver to the engine. This input is simply derived from a potentiometer mounted on the throttle's butterfly valve. The potentiometer is connected to ground on one side, and 5 volts on the other. The wiper contact is connected directly to one of the microcontroller's analog input channels. This gives a voltage close to zero with the throttle at idle and close to 5 volts when at full throttle. With My16M this maps to a value between 0 and 8 in increments of 1/128. The idle value turns out to be 0.9. Cruising at around 80km/h gives about 2.