The Effect of Fuel Manifold Injection and Injection Timing on Performance and Emissions for a Spark Ignition Engine

A fuel injection study was performed on a Briggs and Stratton SI engine rated at 3.73 kW. By switching to a fuel injection system, the operational range was extended over an equivalence ratio, ϕ, range of 0.72 to 1.40. The maximum brake thermal efficiency and minimum bsfc of 24% and 331 g/kWh respectively occurred at ϕ = 0.93. However, the best operating condition to meet high performance and current emission requirements occurs at ϕ = 1.10. Performance and emission results of the baseline tests were compared to those obtained through variation of the injection timing between 29°BTDC and 49°ATDC. It was concluded that injection timing had no significant effect on any engine performance or emissions as long as the equivalence ratio is held constant.