Atmospheric Correction

Atmospheric correction is a necessary feature in any dynamometer. Atmospheric correction ‘adjusts’ the Power and Torque measured by the dynamometer, to the equivalent Power and Torque acquired if the vehicle were operating under International Standard Atmospheric Conditions.
The use of atmospheric correction enables test results from vehicles tested under different atmospheric conditions, to be compared on equal terms.
Atmospheric correction is necessary when performing back to back testing (especially on different days). For example, if a vehicle is tested on a cold (10°C) day it will perform better than when tested on a hot (40°) day. When atmospheric correction is applied to both tests, the results will be equal, assuming all other parameters are constant.
The International Standard Atmospheric conditions (SAE J1349) are:
Barometric Pressure: 101.4kPa
Relative Humidity: 75%
Air Temperature: 16.0°C
It should be noted that some dynamometer manufacturers use J607.
This SAE standard was cancelled in August 1988 (and replaced with J1349) and was only ever intended for small gasoline engines of 50ci or less and 20hp or less power output
The fact that some dynamometer manufactures and operators still use this standard makes you ask the question...Why? Is it because in inflates the horsepower readings by approximately 4%, therefore misleading their customers.