The Hydraulic Water Brake Dyno

A hydraulic dynamometer is a type of dynamometer that uses hydraulic power to test the engine of a machine. Many hydraulic dynamometers work in conjunction with other testing processes, such as the water brake dynamometer. The hydraulic part of the dyno machine applies the necessary load on the engine that helps create a true horsepower reading, and the water brake part of the dyno machine actually measures the horsepower of the engine.
A water brake dynamometer is a special kind of dyno machine that records the horsepower of the machine by recording the temperature changes in the water shot inside the unit. This is accomplished in the following steps:
The machine has rotor and stator pockets designed to catch the water as it rotates around the machine. The stator brings the water into the dyno machine and discharged in the center of the rotor assembly. The water then travels into the pockets on the rotor.
When the rotor accelerates during rotation, the water flies out of the rotor and travels into pockets placed in the stator plates. The water then drains out of the stator plates and travels back into the rotor pockets and accelerated once more. The more this process occurs, the hotter the water gets. This creates a thermal exchange between the engine power and frictional heating of the water.
Since horsepower can be translated into heat energy, by measuring the BTU output of the water the dyno machine can then determine the horsepower of the engine.
Reading the BTU output from water is a relatively easy mathematical process based purely on the laws of physics. Because the hydraulic dynamometer with a water brake uses this simple mathematical formula, it is a popular choice for engine dynos and can obtain highly accurate readings.