Fuel Economy Improvement by Optimized Intake-Port Configuration and Comprehensive Specifications

In order to improve fuel consumption of a four-stroke engine while maintaining the original power output, modifications to several components were tested. First, three types of modified intake port configurations were examined: swirl, tumble and swirl-tumble types. These configurations were examined for their effect on in-cylinder vortex intensity and flow coefficient, which were good indicators of Brake Specific Fuel Consumption (BSFC) and Brake Mean Effective Pressure (BMEP). The tumble-type port showed a good balance of both factors and led to low BSFC and high BMEP. Second, the effect of a bowl-cavity modification to the piston crown, together with the tumble port configuration, enhanced BSFC improvement in high load conditions. This combination also allowed over-lap of valve-timing to be shortened, in order to reduce BSFC in low load condition. Finally, a comprehensive modification package, which included long-duration spark ignition, high compression ratio and a cylinder head with revised squish area, together with the above specifications, were effective in all test conditions and achieved a fuel consumption reduction of 22.6% in the ECE40 driving-mode cycle.