Analisis Pengaruh Bore Up Terhadap Performa Mesin Sepeda Motor 4 Langkah Dengan Variasi Piston Datar (Flat) Dan Piston Cembung (Dome)

Abstract

Besides being a means of transportation, motorcycles are also used for performance competitions. Increasing engine performance for competition purposes requires the selection of piston crown shapes, which greatly determine power output, torque, and combustion efficiency. This study aims to analyze the effect of bore-up modification on the performance of a four-stroke motorcycle engine through variations of piston shapes, namely flat piston and dome piston. The method used involved experimental testing of the two piston shapes on a bore-up engine using a dynotest. The results showed that the dome piston produced a higher compression ratio of 13.07:1, while the flat piston was 11.61:1. The type of fuel used was Pertamax Turbo RON 98, which is suitable for a compression ratio range of 11:1 to 13:1. In terms of performance, the dome piston produced maximum power of 15.205 kW at 10,000 rpm, maximum torque of 15.27 Nm at 5,500 rpm, and MEP of 966.328 kPa. These values are higher than the flat piston, which produced maximum power of 13.400 kW at 9,500 rpm, torque of 14.60 Nm, and MEP of 923.462 kPa. However, the SFC values of the dome piston were consistently higher than those of the flat piston. At 4,000 rpm, the dome piston produced SFC of 575.650 g/kWh and at 6,000 rpm of 586.368 g/kWh, while the flat piston only produced 325.442 g/kWh at 4,000 rpm and 320.307 g/kWh at 6,000 rpm. In terms of thermal efficiency, the flat piston showed better performance with values of 24.62% at 4,000 rpm and 24.85% at 6,000 rpm, while the dome piston only reached 13.83% at 4,000 rpm and 13.57% at 6,000 rpm.