Influence of Injection Timing on In-Cylinder Fuel Distribution in a Honda VTEC-E Engine

Measurements are presented of droplet characteristics and air velocity in the cylinder of a 0.36 litre four valve engine, equipped with an sohc VTEC-E valve train and port injection. The results

show that injection at crank angles, θ_inj(s), when the inlet valve is open results in most of the liquid volume flux being in the form of droplets with Sauter mean diameter between 20 and 30 mm which strikes the sleeve up to about 2.5 cm below the exhaust valves, thus generating a locally rich cloud there. The amount of liquid phase gasoline passing through the plane 16 mm below the spark plug gap increases with θ_inj(s) up to 50 CA after intake TDC and this, together with the crank angle of droplet arrival and vapour generation, controls stratification of the gaseous fuel phase. The optimum injection time is when the fuel-rich cloud is generated so that the tumble vortex convects it to the spark plug at the time of ignition.