I was doing some searching and found this on LS1tech.com... which apparently came from a Cobalt forum... I take no responsibility for it's accuracy. So my executive summary goes like this... Uncorrected= real whp generated that day regardless of weather conditions... Your car might make 300WHP uncorrected on a day in February with 50 degrees ambient air. SAE= 280WHP (corrected to 29.23 InHg and 77 degrees F) STD= 287WHP (corrected to 29.92 InHg and 60 degrees F) My other reading indicates that STD ALWAYS reads 2.6% higher than SAE. I am COMPLETELY unclear on how big the change (%-wise) from uncorrected to SAE/STD is... Would love to hear input from the tuners on the board. There are few standards used in the dyno world for gathering HP and TQ numbers, UNCORRECTED, SAE and STD. Uncorrected is NEVER accepted in the world of dynoing and tuning as it does not factor in any weather conditions etc. Now here is where the big debate comes...is between SAE and STD. SAE (Society of Automotive Engineers) is the MOST ACCURATE AND WIDELY ACCEPTED FORM OF MEASUREMENT when it comes to the world of dynoing. Here is some more info I have gathered between the two..... A lot of people have been asking about SAE .vs STD Dyno numbers so I thought this would help. Most people know that showing STD numbers read higher but not many know why. SAE represents more realistic standard conditions, STD artificially boosts numbers. Identifying Your Correction Factor: Dynojet: If you look at a dynojet graph in the upper right corner, you will see where it says the correction method being used. The options are SAE, STD, Uncorrected and a few not needed for discussion. You will also notice a smooth factor (up to 5) which dyno operators use to make the power curves and any other data displayed, such as AFR, seem more accurate and smooth. You will also see AFR graphs scaled DOWN to hide flaws in the curve. MD: A Mustang Dyno ONLY uses SAE Corrections. Smoothing can also be controlled as well as scale for the Graphical Outputs. Overview: Most of the stated horsepower numbers are “Corrected” values. 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 (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque. STD: STD is Another power correction standard determined by the SAE. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard."