STP Corrected Dyno Results

[SoCalBlk03]

Originally posted by Bob Cosby
FWIW, I am not intentionally "ripping" on anybody or their ride. I am merely trying to clear up a few things.

My personal opinion on dyno's is that they are excellent tuning tools - little else. They are great for seeing what mods work, what tuning works, etc. I don't put much stock in the absolute numbers.

I understand but it does get a little frustrating when the first thing some people say is "That's gotta be wrong" or "there's no way......".

As far as it being a tool to use, I agree 110% If Tetge, whom I've raced many times and live near decided to mod his car to mirror mine. Then he knows he could pick up approx 70rwhp and 50 rwtq given we dyno'd on the same machine at the same place. I never did a true unmodded baseline so I'll never know how much I gained but atleast he knows what this combo should give someone now.

 

[mnypit]

Originally posted by Bob Cosby
My personal opinion on dyno's is that they are excellent tuning tools - little else. They are great for seeing what mods work, what tuning works, etc. I don't put much stock in the absolute numbers.

Here here!! If dynos were the end all of information, we wouldnt need race tracks and drag strips would we?

Steve

 

[Joe Lynch]

We're not ripping anything. The various dyno numbers get kicked around all the time. We've been there, done that, that's all. The more you know about how the calculations are done, the better you can feel about the numbers you have.

Any dyno operator that tries to estimate drive train losses for you is dreaming. He measures power at the rear wheels. Period.

Also, record the humidity along with the barometric pressure and temperature if you ever want to check the correction factor used in converting your actual numbers to SAE or STD. The partial pressure of the water vapor has to be subtracted from the absolute station pressure.

Input errors for temperature and humidity and pressure on dyno run data are common. That's why the data gets challenged.

Joe Lynch

 

[slow lane]

Add another issue to R&E's reporting of numbers....

The 15% TirLos Tetge quoted above is supposed to be tire friction loss in the WinDyn software (defaulted to 2%). A separate input for drivetrain efficiency should be labeled "DrvEff". These two factors are calculated together to back into SAE flywheel horsepower numbers (labeled STP).

If R&E set the TirLos to 15%, a setting of 92% DrvEff would explain the differences between the wheel horsepower and the flywheel horsepower in SoCalBlk03's numbers.

 

[Joe Lynch]

Then they are just playing with numbers. Forget trying to determine flywheel hp from a chassis dyno.
Joe Lynch