STILLEN 370Z Supercharger System - Announcement!!!

RCZ

The "SAE Air Correction Factor" which is used by all the dyno guys is:

SAE CF = 1.18[Ps/(Pm-Pv)][sqrt(Tm/Ts)]-0.18
(sqrt = square root)

This formula is right out of SAE Paper #J1349 (revision June 1990), and is the latest form of the air correction formula. SAE assumes 15% frictional loss within the engine, which is probably close for a piston engine. NOTE: this is NOT the losses from the crankshaft to the rear wheels, that is a different loss.

Ps = standard pressure
Pm = measured pressure (barometric pressure)
Pv = vapor pressure of water (relates to RH%)
Ts = standard temperature
Tm = measured temperature

The SAE baseline values are:
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Ps = 29.235 inHg
Ts = 77.0 deg F (534 deg R)
Pv = 0 inHg (dry air, no humidity)

Pv will not be 0 inHg during a dyno run, but will equate to the vapor pressure of water vapor in the air, which is a function of humidity.

P units = inHg
T units = deg R (deg F + 460). If not in deg R, you will get a wrong answer!

So, the CF will depend on where the actual air temperature, pressure and humidity is with respect the standard values listed above.

The CF can be less than, or more than 1.00. If you tested your Z06 on a dyno on a day when T = 77 deg F, P = 29.325 and the RH = 0% in the shop where the dyno was, then the CF would be exactly 1.00. As you can see, there are MANY combinations of T, P and RH that will give you the same CF.

Note, the Pv (vapor pressure of water) defines the RH% and is subtracted from the atmospheric pressure because the water vapor "displaces" that much pressure, and essentially makes it equivalent dry air (RH = 0%) at the resulting pressure of Pm - Pv.

BTW, the pressure values in the formula has more effect on HP than the temperature values (square root of a ratio)

Source: z06vette.com

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Yes Stillen Math. My correction was of 5.3% according to the dynojet.

You know, with an attitude like yours, I'm glad you're having so many problems.