This article has presented the inlet port diameter-bore ratios (IPD/B) on engine performance and emission characteristics. For the first time, the effect of inlet port diameter-bore ratio on the residual gas, peak firing pressure rise and effective release energy were discussed. Through combined experimental and simulative methods the drawbacks of hardware optimization method were eliminated. The results of the research show that the IPD/B ratio has a significant effect on the residual gas, peak firing pressure rise and effective release energy. Following increased IPD/B ratio from 0.3 – 0.5. The residual gas ratio shows an uptrend from 0.11% to 0.14%. The effective release energy increases from 0.33 KJ to maximum value of 0.45 KJ after that decrease. At IPD/B ratio is 0.4 effective release energy achieved the maximum values. The HC and CO emission was decreased, but the NOx was increased until a maximum value was achieved after that, a subsequent decrease. At IPD/B ratio is 0.4 the NOx was maximum value of 0.66 g/kWh, the BSFC was minimum value of 849.5 g/kWh.
Keywords IPD/B ratio, residual gas, effective release energy, engine emission characteristics.