Chain Load Optimization through Fuel Pump Lobe Phasing and CAE Simulations for a BS6 Compliant Diesel Engine

The introduction of CAFE (Corporate Average Fuel Economy) norms has put a lot of importance on improving the fuel economy of passenger car vehicles. One of the areas to improve the fuel economy is by reducing engine friction. Camshaft drive torque reduction is one such area that helps in engine friction reduction. This paper explains the camshaft drive torque optimization work done on a passenger car Diesel engine with DOHC (double overhead camshaft). The exhaust camshaft of the engine drives the high-pressure Fuel Injection Pump (FIP) in addition to valve actuation. Camshaft drive torque is reduced by reducing the chain load. This is done through optimum phasing of the FIP lobe that drives the fuel injection pump and the cam lobe actuating the exhaust valves. Additional boundary condition for the phasing is ensuring that the FIP lobe is in the fall region of its profile while the piston is at TDC. This helps in avoiding rail pressure fluctuation. This work is done on the BS VI variant of the engine and results are also compared with the BS IV version of the same engine. Changes in the fuel injection system are also explained. CAE simulations were performed to identify the FIP lobe orientation where the addition of FIP load along with valve train loads results in lowest chain load. Finalizing the FIP lobe orientation led to the re-design of FIP housing which was done successfully. Based on the above optimization the finalized design of camshaft with FIP lobe and chain system was validated in both engine testbed and vehicle conditions successfully. Chain loads are also measured on the engine and they are compared against the simulation results.