[eschaider]

The reason OEM auto manufacturers use Mass Air Flow fueling models in their production EFI systems its that they measure the actual mass of air the engine consumes allowing the EFI system to exactly match the correct amount of fuel to the incoming air charge to maintain the target air fuel ratio the original calibrators wanted for the engine.

This approach means the engine will meet emission standards everywhere and anywhere on the planet irrespective of altitude, temperature, or barometric changes hour to hour. Only Mass Air based systems can do this because only Mass Air based systems directly measure the air mass actually entering the engine.

When you operate the engine at higher altitudes, although the throttle response will remain the same, power output will diminish because of reduced air supply (thinner air). An internal combustion engine requires 10 lbs of air per minute, properly fueled, to produce 100 hp. When you go to higher altitudes and the air density decreases, so to does the amount of air the engine injests and therefore so to does the horsepower. That's why piston engine powered aircraft used Turbos and Centris. They replace the air mass lost at altitude so the engine has comparable power to what it had at lower altitude.


Ed