This SAE Recommended Practice is intended for use as a test procedure to determine the gaseous emission level of diesel engines. Its purpose is to provide a map of an engine's emissions characteristics which, through use of the proper weighing factors, can be used as a measure of that engine's emission levels under various applications. The emission results for hydrocarbons, nitrogen oxides, carbon monoxide, and carbon dioxide are expressed in units of grams per kilowatt hour (grams/brake horsepower hour) and represent the mass rate of emissions per unit of work accomplished.

The emissions are measured in accordance with SAE Recommended practices J177, J215, and J244 using nondispersive infrared equipment for CO and CO2, a heated flame ionization analyzer for HC, and a high performance NDIR or a chemiluminescence analyzer for NO\dx. All emissions are measured during steady-state engine operation. The mass rate of emissions is calculated (a) from the concentration in the exhaust gas and the exhaust flow for each mode or (b) alternately, using a carbon balance method, from the concentration in the exhaust gas and the mass flow rate of fuel for each mode. If method (a) is used, CO\d2 should be measured for data validation. The final emissions are calculated by dividing the summation of the weighted emission mass rates by the summation of the weighted brake power values for a cycle.