/\ Ur right croz. Here is a description copied from another one of my forums. It explains the difference in more detali:
SAE -- The SAE standard applied is a modified version of the SAE J1349 standard of June 1990. 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. Friction torque can be determined by measurements on special motoring dynamometers (which is only practical in research environments) or can be estimated. When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%). SuperFlow uses a more sophisticated algorithm for calculating friction torque, based on a summary of thousands of friction power tests performed by the automotive industry. This proprietary algorithm estimates friction torque as a function of piston speed and engine displacement.
STP -- The STP (also called STD) standard is another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. 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. Once again, this means the STP corrected power displayed by your SuperFlow test system will be more accurate than power numbers obtained using a default Mechanical Efficiency of 100% or 85%.
No explanation necessary. Guess you are all done with finals and have little time on your hands. Looking forward to seeing you and your brother for the Christmas holiday. Drive defensively and be safe. Roads are going to be a little slick on the way home.