A few weeks ago, one of the drag racers completed competition with a bracket blown alcohol 7.60 second ET setup. It was close to maxed out with a small 0.040 inch main bypass jet in his fuel injection setup. The main bypass jet is used to return excess fuel to the fuel tank. In this case, there was not much excess fuel. The engine was running on most of the methanol for the run.
Using air/fuel ratio data in our nitro book for various percentages, the racer’s setup was examined with ProCalc to determine how much nitro could be run if the main bypass jet was blocked off. In this case, all of the fuel would be run to the engine. A quick computation revealed 10% nitro by volume was the limit with his fuel injection setup. After the removal of the main bypass and that addition of nitro to the fuel tank, he went out and ran a couple 7.3 second ETs with 6 MPH increase in speed. The engine ran clean and made a lot of power.