Would a supercharger give you more or less MPG

[FoxGT]

Originally Posted by i8acobra When I say P&P, I mean just cleaning up and reshaping to reduce friction. Not hogging out. More air requires more fuel or you go lean and break s**t. The goal is just to decrease frictional losses. Ah. Too true then. Running lean isn't a bad thing. Running lean at higher throttle loads is bad. At partial throttle like cruise & idle running lean is better. The leaner your a/f ratio the more energy it's going to make. Gasoline's stoichiometric ratio of 14.7 has nothing to do with power or fuel economy. The reason car companies aim for it is because you get the least emissions at that rate. Running more lean than that will result in better fuel economy, but higher emissions. The only reason for running rich is because if you did run lean the temperatures would skyrocket & cause damage from the heat. Most n/a cars will run around 13:1 at wot to keep the temperature down at a loss of power. What I will usually do for other people's cars if they want the fuel economy is lean it out to the point where it starts surging (most cases it's around 16.5-17.1) then back it off 2 points. So say I lean it out to 16.8:1 & it drives fine. I would go to 16.9. If it starts surging at that I would back it off to 16.7. A lot of people think you'll burn up your engine at numbers like that which isn't true, there isn't enough air/fuel mixture to create high temperatures to cause damage. At wot, that's another story.

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