Here is the answer, straight form the software manager at Mustang Dynos (and creator of the ingenious Mr.Dyno performance tester):
"The standard Weather Correction Factor logic is not appropriate for turbocharged applications with waste-gate controlled boost levels. This is because a waste-gate controlled turbocharged application will maintain intake manifold pressure regardless of atmostpheric pressure (within their abilities).
For vehicles with relative pressure control (most vehicles), you may wish to calculate your atmospheric pressure as shown below – this will provide a reasonable estimate of the required pressure-based correction factor, but will only be valid at maximum boost pressure.
Pressure = 29.235 * [(ActLocPressInHg + (2.036 * MaxBoostPSI)) / (29.235 + (2.036 * MaxBoostPSI))]
Where
ActLocPressInHg = Actual local pressure, in inches-Hg
MaxBoostPSI = Maximum boost pressure, in PSIG
For example, for a vehicle running 10 PSIG of boost, with a local pressure of 28.000 InHg:
Pressure = 29.235 * [(28.000 + (2.036 * 10)) / (29.235 + (2.036 * 10))]
Pressure = 29.235 * [(28.000 + 20.36) / (29.235 + 20.36)]
Pressure = 29.235 * [48.36 / 49.595]
Pressure = 29.235 * [0.9751]
Pressure = 28.507
So, you would enter 28.507 InHg, rather than the actual local pressure of 28.000 InHg. This will result in a smaller Weather Correction Factor adjustment, which is correct, since the ratio of actual-boosted-pressure to standard-boosted-pressure is much closer to 1.000 than the ratio of actual-unboosted-pressure to standard-unboosted-pressure.
For vehicles with absolute pressure control (relatively uncommon), it is recommended that the pressure and altitude be entered as 29.235 and 0 respectively, to prevent the use of those values in the Weather Correction Factor logic.
Performing Weather Correction Factor logic on turbocharged applications in general is much more difficult than on naturally aspirated vehicles. Unless you know quite a bit about the characteristics of your turbocharger and the associated controls, any correction factor is only an estimate of standard corrected power output. To perform accurate corrections on such a vehicle you would need actual measured values for intake manifold pressure, possibly intake manifold temperature, turbocharger RPM, and the performance map for the turbocharger used."
"The standard Weather Correction Factor logic is not appropriate for turbocharged applications with waste-gate controlled boost levels. This is because a waste-gate controlled turbocharged application will maintain intake manifold pressure regardless of atmostpheric pressure (within their abilities).
For vehicles with relative pressure control (most vehicles), you may wish to calculate your atmospheric pressure as shown below – this will provide a reasonable estimate of the required pressure-based correction factor, but will only be valid at maximum boost pressure.
Pressure = 29.235 * [(ActLocPressInHg + (2.036 * MaxBoostPSI)) / (29.235 + (2.036 * MaxBoostPSI))]
Where
ActLocPressInHg = Actual local pressure, in inches-Hg
MaxBoostPSI = Maximum boost pressure, in PSIG
For example, for a vehicle running 10 PSIG of boost, with a local pressure of 28.000 InHg:
Pressure = 29.235 * [(28.000 + (2.036 * 10)) / (29.235 + (2.036 * 10))]
Pressure = 29.235 * [(28.000 + 20.36) / (29.235 + 20.36)]
Pressure = 29.235 * [48.36 / 49.595]
Pressure = 29.235 * [0.9751]
Pressure = 28.507
So, you would enter 28.507 InHg, rather than the actual local pressure of 28.000 InHg. This will result in a smaller Weather Correction Factor adjustment, which is correct, since the ratio of actual-boosted-pressure to standard-boosted-pressure is much closer to 1.000 than the ratio of actual-unboosted-pressure to standard-unboosted-pressure.
For vehicles with absolute pressure control (relatively uncommon), it is recommended that the pressure and altitude be entered as 29.235 and 0 respectively, to prevent the use of those values in the Weather Correction Factor logic.
Performing Weather Correction Factor logic on turbocharged applications in general is much more difficult than on naturally aspirated vehicles. Unless you know quite a bit about the characteristics of your turbocharger and the associated controls, any correction factor is only an estimate of standard corrected power output. To perform accurate corrections on such a vehicle you would need actual measured values for intake manifold pressure, possibly intake manifold temperature, turbocharger RPM, and the performance map for the turbocharger used."
Comment