Dynos measure engine performance by running an engine at high speeds for long intervals. Dynos are different than road tests, though, in the vehicle is placed on stationary rollers and can be controlled by a computer.
Some dyno varieties involve a frame that holds the vehicle above engine mounts, rolling cylinders, a heat exchanger and a torque measuring device. Others require hydraulic fluid, water or oil to function.
Modern dynomometers are able to graph the performance of an engine in terms of its maximum rotary speed, torque capacity and maximum power absorption. In some cases, they can also provide analyses of emissions and reaction time. Dyno users can interface with their equipment through control consoles, computers or remote controls.
Dynomometers are used to measure the RPMs and torque for gearboxes, belt or chain drives, fluid power systems, gas or diesel systems, turbines, transmissions and other applications. They are most commonly used in the automotive industry but are also applied in aerospace, marine and industrial processes.
Chassis and engine dynomometers are the most common dyno varieties. Chassis dynos measure an engine’s performance based on the speed and nature of the rotation of the wheels that the engine powers; engine dynos measure engine performance directly.
In the case of chassis dynomometers, a vehicle is placed on a frame and placed on rollers. Once secured, a computer starts the vehicle’s engine remotely. The computer measures how quickly the rollers rotate and, along with factoring in the weight of the rollers, determines the engine’s performance.
Chassis dyno readings can be 15% to 20% lower than readings taken by engine dynomometers because the chassis dynamometer reading process causes energy losses due to friction throughout the drivetrain.
In engine dynos, a torque measuring device is connected to the crankshaft or flywheel, and a lubricant may be used to reduce friction and heat generation. Dynos are often used to test new engines or to examine engines during diagnostic testing.