Manual Transmission and Transaxle Efficiency and Parasitic Loss Measurement
Because of the intense focus on CAFE and fuel emission standards, optimization of the automobile drivetrain is imperative. In light of this, component efficiencies have become an important factor in the drivetrain decision-making process. It has therefore become necessary to develop a universal standard to judge transmission efficiency.
This SAE Recommended Practice specifies the dynamometer test procedure which maps a manual transmission's efficiency. The document is separated into two parts. The first compares input and output torque throughout a specified input speed range in order to determine 'in-gear' transmission efficiency. The second procedure measures parasitic losses experienced while in neutral at nominal idling speeds and also churning losses while in gear.
The application of this document is intended for passenger car and light truck.
All references to transmissions throughout this document include transaxles.