In-Cylinder Combustion Analysis of a Yamaha R6 FSAE Engine: Achieving Improved Engine Performance and Efficiency through Burn Rate Combustion Diagnostics

Abstract

The actual three-dimensional, turbulent combustion process that occurs in a modern, spark-ignited internal combustion engine is very complex and difficult to model. However, since cylinder pressure is directly related to the combustion event, in-cylinder pressure traces sampled and averaged over multiple cycles can be utilized to provide the burn rate of the air and fuel mixture in the cylinder with respect to crankshaft position. A design of experiment was created to examine the influence of ignition timing, fuel rail pressure, injection timing, and air to fuel ratio on the start of combustion, burn duration, and combustion centroid at various engine operating points. Once the factors controlling the three burn rate profile parameters were understood, they were used to manipulate the combustion event and improve engine performance and efficiency. Through the in-cylinder pressure analysis performed, an indicated specific fuel consumption of 0.469 lbm/hp-hr and an indicated mean effective pressure of 43 psi were realized for the 15% load, 3,000 rpm operating point. An indicated specific fuel consumption of 0.356 lbm/hp-hr and an indicated mean effective pressure of 88 psi were achieved for the 60% load, 3,000 rpm operating point. The study was performed on a 599 cc Yamaha R6, four stroke, inline four cylinder, naturally aspirated, spark ignition engine with a restricted intake for use in Formula SAE competition.