40 CFR 89.331 - Test conditions.
(a) General requirements. Calculate all volumes and volumetric flow rates at standard conditions for temperature and pressure (0 °C and 101.3 kPa), and these conditions must be used consistently throughout all calculations.
(b) Engine test conditions. Measure the absolute temperature (designated as T and expressed in Kelvin) of the engine air at the inlet to the engine, and the dry atmospheric pressure (designated as p and expressed in kPa), and determine the parameter f according to the following provisions:
(1) Naturally aspirated and mechanically supercharged engines:
(2) Turbocharged engine with or without cooling of inlet air:
(c) For a test to be recognized as valid, the parameter f shall be between the limits as shown below: