Why do I see so many SAE corrected numbers on MCS dyno runs? Though the correction factor is fairly small, It's my understanding that these corrections are not applicable to forced induction engines.

 

SAE correction factors, like J1349 currently used for OEM production vehicles, are used to give a more level playing field in comparing dyno figures. They factor in temperature, atmospheric pressure, and sometimes humidity. The correction factor calculates the power the car would have made under standard atmospheric conditions. An example is on a hot day in Denver a car will make much less power than a cold winter day in Detroit.

You probably heard that "not applicable" statement from Randy Webb. He got confused when he initally dyno'd his new R56 turbo MCS. Turbo engines are usually set up so they make a certain amount of boost over atmospheric. Supercharged cars however, being belt driven, always make a certain ratio over atmospheric. The difference between the two setups at high elevation shows up dramatically. A turbo car will make almost as much power at elevation as it does at sea level, whereas a supercharged car will make much less power. Creating a useful correction factor for a turbo car at high elevation is tricky.

 

I've actually heard/read it in many places, pretty much anywhere you look, they say that SAE correction is for normally aspirated engines. Maybe they're only thinking about turbos though.