Borrowed from BryanL:
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. 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%).
STD or STP 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.
Was his dyno sheet not labeled STD and 5th gear run.csoday said:. Neither method is inflating or deflating, they are apples and oranges and as long as the graphs are labled STD or SAE no one is trying to bullshit you. You just interpret them for what they are.
JuggsItis my build was done last July, I am happy with it but If i had to it over again I would of used different cams. I wish I would of found this site before the build because of the knowledge I got from reading about other members builds. This was my first twin cam and first 95. I basically relied on the dealer's suggestions. The bike runs very well but the powerband comes in above 2500, I would of like it to start above idle. I will probably change them out again when the warranty is out. Hope this helped ...... Mike........JuggsItis said:Chi-Town
I just did my build in Feb. Too cold to ride much, but liked what I've seen so far. When did you do yours, how do you like it?
Interesting theory and around here, I have noted some newer, very nice dyno rooms. Modern, very well ventilated. Haven't asked about temperature control, but I'd assume they are. Could very well be that STD in a lot of cases is closer to the actual power produced.csoday said:I had posted this in a PM but repeating it here. It's my theory and it is along the lines of the above post by MTclassic.
With todays technological advances in dynos and climate controlled booths, built in correction factors are becoming outdated. SAE assumes the dynos are less than 85% effecient over the band and that atmospheric conditions are less than nominal. Many tuners today are more particular of their machines calibrations and in the gulf coast area are installing booths that are damn near medical quality. Due to that, I don't put any creedence in a 4% assumption. Many of these tuners consider STD to be a more accurate measurement. They do mark their charts accordingly. There is no missleading or dishonesty as long as that is noted.