A Superflow 901 stationary dyno operates in the following way. Water is pumped through a water brake (pump) by the engine being tested, a strain guage is mounted on this brake (pump) as this strain guage separates data is taken, the more the separation on the strain guage, the more power is being made. This data is called raw or observed data, Superflow calls this measured data. From here is where the data is corrected, this how you can test an engine in Florida at sea level, then test the same engine in Utah at 4700 feet and get relative data. And Ive done it several times to prove my point. Back to how the data is corrected, most people that dyno on a 901-902 use a STP correction factor, translated: corrected to 29.92 60 degrees dry air. The computer in the dyno corrects this by the following: it takes the air temp, the corrected barometer, the vapor pressure, the humidity into account then correct to STP (29.92 degree 60 dry air) that is your corrected HP number. The dyno is calibrated by hanging a known weight off the water brake, the TQ is set at .007 HP, the corrected barometer is then entered into the computer, in my case the filter is set at 3. Your then ready to test. Measured or observed or (In the room HP) is calculated this way: Fuel flow is divided by BSFC. Remember fuel flow and BSFC is ALLWAYS based of observed data. Dyno testing in Colorado allways left me wondering how my numbers would stack up to numbers from sea level testing. So Harold Bettes and I put a test together, Harold went through the full calibration testing on my dyno, A pump gas 505 was the then tested, the result 669 HP, the engine was then put in a crate shipped to California to a very well known dyno facility, SuperFlow then sent in their own technician the night before my engine was tested, the calibrations were made by SF, the results 670 HP within 1 HP on a 901 with wyndyn software the same as my setup. These dynos can be very accurate to each other if they are calibrated correctely. Since then we have done these tests in different parts of the country with excellent results.

 

They are amazing machines, for sure. But, just to be clear, they do not measure the HP, it isn't possible. They measure the torque and then convert that reading to HP using the mathematical formula. The dyno also controls the rate of acceleration, which affects the "time" portion of the formula, thus affecting the HP.

That said, a dyno session is a fabulous tuning tool (and a lot of fun!!) and the $ spent will save you time and $ in a track car. Also, using the dyno as a "break-in" procudure will also let you correct minor issues (oil and coolant leaks, rocker adjustments, etc) much easier than if it was in the car.

 

Agreed, its based on TQ. After we test we pretty much know what the car will run, if the car is right.

 

It is amazing how close you get to ET once you get the sheet, using the vehicle weight and of course the car hooking. Helps determine optimum shift points, too. Again, saves a TON of time in track testing.

 

Catnjim, do you see any problem with 519 corrected HP pushing a 3720 pound well set up car to a 119 mph? I say its not even 519 HP. More like 495.

 

According to "Mr Wallace" that is pretty close, assuming good launch, of course. Should run low-mid 11 seconds.

 

I have allways used the Moroso power speed calculator, which is basically the same as Weiss's calculator, because it allways lines up with my dyno testing, when the car and drive line is setup right. 119.8 @ 3720 = 495 HP its not as flattering as Wallace, but its very real.