To OP: I would expect a slight increase in mileage if the numerical ratio is lowered slightly, but switching from a 4.4X:1 to 3.15 or even 3.45:1 might not help mileage. There a are a few factors going on...engine friction typically scales with the square of engine speed, so slowing the engine down does help engine efficiency. Also, at a lower rpm you will need more throttle, reducing the pumping losses across the throttle, which is a good thing. However, at too low of speeds the engine begins to fall off the range where it has good volumetric efficiency. Without having a fueling map of the engine, it's not possible to say for certain - only experiments with good repeatability can decide. |