Recently, needs for driving power of the engine accessories such as Power Steering System (PSS), alternator and air conditioner system have increased. Since these increases bring about additional fuel consumption, the driving power of engine accessories is very important for fuel economy. Therefore studies about the effect of accessories driving power on fuel economy and systematic optimization are necessary for the subject of enhanced fuel economy.
In this study, driving power of PSS was defined as a function of pump pressure, pump rotating speed and oil temperature. In addition, the driving power of cooling fan and alternator was measured. A method to measure driving power for PSS was introduced in the vehicle condition. The method included the engine total friction measurement using cylinder pressure and PSS By-Pass module. And this method was also able to be applied for the driving power of air conditioner system.
Fuel economy analysis was performed with PSS condition and PSS By-Pass condition under FTP-75 Mode. As a result, total injected fuel mass in the PSS By-Pass condition was reduced in 2.1(%) which was 1.4(%) in thermal loss and 0.69(%) in engine total friction loss including accessories driving power.
The comparison with results of experiment and simulation was performed by using the vehicle simulation software (CRUISE, AVL). In addition, the modeling results applied accessory components practical data are compared with the measured results. The result of simulation agrees with that of experiment. And the simulation can be applied to the electric power steering system and air conditioner system.