Originally Posted by bmorecam

When we dyno our car there are 2 major component that most dyno use to calculate accurate result. They are the correction factor and temperature(weather station). There are over half of dozen corrections that can be used but here in USA we only use 2, the STD and SAE. Since there seem to be so much confusion surrounding this 2 calculations I will try to make this as simple as I can for you guys that want to know more about these very important factors that is part of every single dyno.

First, lets understand why these corrections was created in the first place. The correction standards were developed to discount the observed horsepower readings taken at different locations and weather conditions. It is obvious that an engine builder in Colorado could not produce as much horsepower as a shop at sea level. There is just less oxygen for the engine to burn at the higher altitude. What are less obvious are the other weather condition effects on the engine. So in order to compensate for this all advertised horsepower is "corrected" to several different industry standards.

SAE:
"SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg of dry air and 77 F. This SAE standard requires a correction for friction torque.

STD:
STD is Another power correction standard determined by the SAE(society of automotive engineers). Power is corrected to reference conditions of 29.92 InHg of dry air and 60 F. Friction torque is handled in the same way as in the SAE standard."

To sum everything up, both correction factors basically mimic a preset condition which was created by the society of automotive engineers. So... although the SAE correction factor is recognized today as the "standard" correction in the automotive industry, this does not mean reading a dyno number with STD cf is wrong. No matter which correction factor your dyno shop use, you should get an accurate comparison as long as you compare SAE vs SAE and STD vs STD. Never compare a dyno run with two different type of correction.