Performance test bench
Methods of measuring engine torque and power
The problem of testing combustion engines with stationary dynamometers is quite complex. To measure power and torque correctly, several factors must be taken into account. Depending on the purpose and the way in which the dynamometer is used, three basic solutions can be distinguished: inertial measurement (during acceleration), measurement in load mode (during acceleration) and measurement with the balance of forces (braked).
Inertial measurement (measurement method possible on the dynamometer and on the inertial dynamometer)
Inertial measurement consists in first accelerating the car on the roller dynamometer and then, after disengaging the clutch, waiting until the car comes to a standstill without using the brake. The loads on the engine are the roller mass, the rolling resistances and the resistances of the drive unit. The measurement time is approximately 10 to 30 seconds under full load and a few minutes for rolling to a standstill on the dynamometer. Power and torque are measured as functions of the vehicle's acceleration on the rollers (power, torque on the wheels) and its deceleration (power and torque loss). The sum of these results in the result, which is the engine power and torque.
Measurement in dynamic load mode (measurement procedure possible on the power test bench)
Measurement in this mode is similar to inertial mode, with the difference that the eddy current brake simulates a greater load. The load index is a percentage value and is set by the user in the test bench program.
Measurement in dynamic load mode has several significant advantages over inertial measurement:
The user can choose the load himself depending on the type and power of the engine being tested.
The measurement time can be extended.
It is possible to correctly load powerful turbo engines in order to "build up" the correct aftercharge.
The measurement procedure in dynamic load mode is as follows:
In dynamic load mode, the additional load should be set in the test bench program before starting the measurement (this means increasing the apparent inertia of the dynamometer by loading the vehicle with an eddy current brake so that the torque is not compensated). This procedure allows the load to be adjusted to the engine power more precisely, e.g. to "build up" and maintain the correct recharge.
The procedure for the actual measurement, after determining the load index, is identical to that in inertial mode.
The problem of testing combustion engines with stationary dynamometers is quite complex. To measure power and torque correctly, several factors must be taken into account. Depending on the purpose and the way in which the dynamometer is used, three basic solutions can be distinguished: inertial measurement (during acceleration), measurement in load mode (during acceleration) and measurement with the balance of forces (braked).
Inertial measurement (measurement method possible on the dynamometer and on the inertial dynamometer)
Inertial measurement consists in first accelerating the car on the roller dynamometer and then, after disengaging the clutch, waiting until the car comes to a standstill without using the brake. The loads on the engine are the roller mass, the rolling resistances and the resistances of the drive unit. The measurement time is approximately 10 to 30 seconds under full load and a few minutes for rolling to a standstill on the dynamometer. Power and torque are measured as functions of the vehicle's acceleration on the rollers (power, torque on the wheels) and its deceleration (power and torque loss). The sum of these results in the result, which is the engine power and torque.
Measurement in dynamic load mode (measurement procedure possible on the power test bench)
Measurement in this mode is similar to inertial mode, with the difference that the eddy current brake simulates a greater load. The load index is a percentage value and is set by the user in the test bench program.
Measurement in dynamic load mode has several significant advantages over inertial measurement:
The user can choose the load himself depending on the type and power of the engine being tested.
The measurement time can be extended.
It is possible to correctly load powerful turbo engines in order to "build up" the correct aftercharge.
The measurement procedure in dynamic load mode is as follows:
In dynamic load mode, the additional load should be set in the test bench program before starting the measurement (this means increasing the apparent inertia of the dynamometer by loading the vehicle with an eddy current brake so that the torque is not compensated). This procedure allows the load to be adjusted to the engine power more precisely, e.g. to "build up" and maintain the correct recharge.
The procedure for the actual measurement, after determining the load index, is identical to that in inertial mode.