Chassis Dynamometer Testing
A chassis dynamometer is used to simulate driving on a road inside a laboratory under controlled conditions. The vehicle is driven on rolls, while a dynamometer simulates the inertia of the vehicle as well as the drag and friction on the vehicle (known as "road load" in the vehicle testing community).
Because an entire vehicle is tested instead of just an engine, and a driver controls the vehicle instead of a computer, the use of a chassis dynamometer allows the assessment of "real world" emissions. Chassis dynamometer testing allows a better assessment of the benefits of new fuels and vehicle technologies, and is absolutely essential to assessing the performance of heavy hybrid trucks and buses.
Chassis (Emissions) Dynamometer: A special chassis dynamometer used for emission testing. It is calibrated to accommodate weights of various vehicles, referred to as “inertia weight” categories. These inertia weight categories are divided into125-pound increments to provide the SEMA Black Book - A Guide to Emissions Clarification of Specialty Automotive Aftermarket Products most accurate emission measurements. The dynamometer is also calibrated for various road load horsepower (RLHP) settings to simulate the amount of horsepower required to move the vehicle over a level road surface at 50 miles per.