Question: Fuel injection adjustment with launch controls for a torque converter racecar
Answer: When a mechanical fuel injection throttle is part open, such as in preparation for launching from the starting line using throttle control setups, the air to fuel ratio is dependent on that throttle position at the time just before the launch. Part throttle in the fuel injection barrel or metering valve enables different bypasses. Those subtract the amount of fuel going to the engine. Every bit as important as stablizing the engine with throttle control or two step is the location of the metering valve spool at that stable position, just before the hit. In some combinations of bypasses, poppets, and launch RPM, it is possible to be lean at part throttle regardless of whether the engine is rich at wide open throttle or not. The leanness or richness at launch can change at a different launch RPM such as a change of converter stall speed or a change in a launch rev limiter setting. That also explains why one setup launches in 0.9 seconds when another with the same amount of launch control does not. This is more fully explained in Fuel Injection Racing Secrets.