DOWNSIZING OF A NATURALLY ASPIRATED ENGINE TO TURBOCHARGED GASOLINE DIRECT INJECTION VARIABLE VALVE TIMING ENGINE

The need to reduce CO2 emissions and fuel consumption has become the biggest aim of Original Equipment Manufacturers (OEM’s) over the past decade. Different strategies are being sought after to comply with stringent emission regulations being enforced on the global automotive market. Engine downsizing is proving to be the most cost-effective method of reducing emissions and fuel consumption. This paper presents 1-D CFD simulation using Ricardo WAVE of 30 % downsizing on a 2.0 litre naturally aspirated spark ignition engine to a 1.4 litre turbocharged gasoline direct injection variable valve timing engine. Performance improvement has been achieved by using turbocharging and variable valve technology. Turbocharging a spark ignition engine increases the intake temperature and pressure, causing the mixture to detonate. To prevent engine mixture detonation, direct injection has been used, which also allows an increase in the compression ratio. The downsized engine has been optimised for maximum volumetric efficiency, maximum brake mean effective pressure and knock elimination. Valve opening timing, their durations and lifts have been optimised to improve volumetric efficiency. Fuel-air ratio and start of injection timing have also been optimised to improve the maximum brake mean effective pressure. The results indicated 74 % improvement in torque, 102 % improvemen