[eschaider]

A couple more thoughts on correction factors for inquisitive minds:

The primary reason a correction factor is employed is to compare testing performed under different atmospheric conditions, high altitude (Denver?) vs low altitude (Coastal Cities) including ambient air temps less the impact of humidity. The correction factor will contain a temperature, barometric pressure and an efficiency percentage that is used to bring all test results to a level playing field.

There are two different correction factors that Detroit has used for 'normalizing' dyno results. One is the SAE J607 correction factor that corrects to 60˚F and 29.92 inches of mercury. The second SAE correction factor is J1349 which corrects to 77˚F and 29.31 inches of mercury.

In both cases wet bulb readings are used to calculate a saturated, current and corrected vapor pressure. The corrected vapor pressure is then subtracted from the observed barometric pressure because this pressure in the ambient air is attributable to water vapor and not air (remember the 10 lbs per minute per 100 HP metric) This methodology will yield corrected barometric pressure.

The corrected barometric pressure is used to calculate the correction factor for each standard. Once the correction factor has been determined the observed dyno power is multiplied by the correction factor to get the corrected power output.

Now for those inquiring minds the actual correction factors are calculated as follows:

J607 Correction Factor Calculation

........CF= [(29.92/Corr Baro)^(1.2)*{(Inlet Air Temp+460)/(520)}^0.6]


J1349 Correction Factor Calculation

........CF= 1.18*[(29.31/corr Baro)*{(Inlet Air Temp+460)/(537)} ^0.5]-0.18

The easiest thing to remember is cooler air and higher barometers produce more power and hotter air and lower barometers produce less power. This is why legit shops use correction factors to normalize measured power irrespective of atmospheric conditions at the time of the test.


Ed