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The mechanical energy of an engine is lost by engine friction and in driving the engine's auxiliary components, which is then transferred to transmission. Thus, it is very important to know the exact value of engine friction and the driving torque of engine's auxiliary components in order to reduce fuel consumption of an engine by reducing these losses. And, it is also helpful to know the braking torque of an engine in actual vehicle so as to improve vehicle's driving performance. For these reasons, present study developed an engine torquemeter for in-vehicle application, and measured braking torque of an engine in vehicle and analyzed fuel consumption contributions of engine's auxiliary components.

The engine indicated torque is not delivered entirely to the wheels, because it is lowered by losses, such as the pumping, mechanical friction and front auxiliary power consumption. The front auxiliary belt drive system is a big power consumer-fueling and operating the various accessory devices, such as air conditioning compressor, electric alternator, and power steering pump. The standard fuel economy test does not consider the auxiliary driving torque when it is activated during the actual driving condition and it is considered a five-cycle correction factor only. Therefore, research on improving the front end auxiliary drive (FEAD) system is still relevant in the immediate future, particularly regarding the air conditioning compressor and the electric alternator. An exertion to minimize the auxiliary loss is much smaller than the sustained effort required to reduce engine friction loss.