There are several types of dynamometer testing styles used to measure the horsepower and torque of an engine, the thrust of a boat propeller and the dampening characteristics of a shock absorber. Chassis dynamometers are able to identify the power reaching the drive tires. Shock absorber dynamometers measure the force required to compress the shock absorber as well as the amount of pressure the shock requires to rebound.
The final step in most high-performance engine building is dynamometer testing to not only break in the fresh engine components, but to measure the horsepower and torque produced by the engine. After making an initial pull on the dynomometer to get a baseline power measurement, fine tuning of the fuel delivery system and adjustment of the spark timing can be manipulated to achieve the maximum performance from the engine. This dynamometer testing only measures the output of the engine and has no relevance to the power levels the engine might make when measured at the drive tires.
A more realistic dynamometer testing is made using a chassis dynamometer. With the chassis dynamometer, the engine is placed into the vehicle it was built for and the vehicle is strapped to the dynamometer with the drive tires positioned on top of large rollers. The rollers are connected to the dynamometer and measure the actual power that the vehicle makes at the tire. This is a real-world testing method to get accurate power level results. Vehicle components, such as the transmission and drive axle, both require a certain amount of power to operate, which results in parasitic power loss from the engine as measured at the flywheel during the engine dynamometer testing.
Much like a chassis dynamometer, a dynamometer specifically for testing propeller thrust is used to measure the output of a marine engine as well as various propeller designs. Likewise, dynamometer testing of racing shock absorbers can test the damping and rebound characteristics of a given shock under simulated on-track conditions. This type of dynamometer testing allows a chassis specialist to set up a vehicle's chassis to take advantage of track conditions based on temperature, vehicle weight and speed. The testing can show minute changes in a shock absorber's performance potential when compared to changes in caster and camber settings of a specific wheel.