·        Water Brake Dyno

A dynamometer (dyno) is a means of measuring the power output of an engine. The basic operation of a water brake dyno uses the principle of viscous coupling. The output shaft of the engine is coupled to a fan that spins inside a concentric housing. While the engine is running, the housing is filled with a controlled amount of water. The more water that is allowed into the housing, the more load the engine will feel. 

As the fan spins through the water, the water is whipped around as well. Newton’s 3^rd Law says that the water will push on by the housing with the equal and opposite force that the fan is pushing on the water. In this case, the shear forces in the water are acting tangential to the housing radius. There is a load cell at a measured distance from the center of the housing.  The load cell is also oriented perpendicular to the arm extending from the housing. The torque output of the engine is just the force measured at the load cell multiplied by the distance to where the extended arm and load cell connect.

There is also a data acquisition system on the dyno. The dyno we use has a Commander II system. The data acquisition system’s sensors measure force, input shaft RPM, oil pressure, fuel pressure, fuel flow rate. From these sensors, ‘math channels’ are set up to calculate whatever you want. A few of the most useful things this system calculates are torque, horsepower, and brake specific fuel consumption. Horsepower is just a function of torque and RPM.