Dynamometer - Potential Engine Damage and Dynamometers

Potential Engine Damage and Dynamometers

A brake dyno in steady state mode only provides a load that is equal to the amount of power that the engine is making at any specifically selected RPM point. If the engine makes 200 brake HP at 5000 RPM, the dynamometer's brake or power absorber will provide exactly 200 hp (150 kW) of load against it, keeping the RPM at 5000 RPM. That is a realistic load that simulates a vehicle pulling a large trailer up a hill. It should be no problem on the dyno if there is no problem on the road.

Apprehension over dyno testing and engine damage has solid roots in fact. Old style dynamometers commonly used an inexpensive water brake type of power absorber. Load was increased or decreased by adding or draining water in the housing to change the amount of internal water volume to change the load, all the while draining and refilling the water to keep the water from boiling. It would sometimes take some time for the operator or computer to stabilize inflow and outflow rates. That extra time could pose a risk to engines. Water brakes are still commonly used in applications where their small size and light weight are important and engine torque curves are relatively straight, as in large automobiles and boats.

Engine testing may damage engines primarily due to insufficient instrumentation, insufficient safety monitoring systems, and insufficient cooling. An engine on a dyno does not receive air cooling. Automotive engines are not typically designed for wide-open throttle operation for extended periods of time, and internal components may thus overheat and fail.