The Peff/Pi Dynamometer has been developed to measure friction changes in a fired production engine in the 10hp range like it is used i.e. in lawnmowers.
Internal friction directly affects the difference between the indicated and effective piston pressure, thus by determining both pressures, friction changes can be detected. Peff is measured via a high accuracy torque sensor, Pi with a spark plug integrated pressure sensor. The engine is loaded with an AC-Motor controlled by a vector oriented variable field drive. The engine throttle is set by a closed loop Pi-servo-control, allowing for ambient independent operation.
Tested have demonstrated the effects of laser dimple modifications to the cylinder liner surface for Friction Reduction at the Piston Cylinder Interface. Peff/Pi comparison is used to evaluate analytically proven modifications (Parasitic Loss Control at the Piston Ring Cylinder Liner Interface through Surface Modifications ) in full scale fired engine applications.