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The gasoline-fuelled direct injection poppet-valved two-stroke engine described in (1) has been built in single cylinder form and tested to evaluate the potential of this concept as a passenger car powerplant. Development of the combustion and scavenge system is described. Following development, the engine produced a specific power output of 90 kW/litre at 5000 rev/min, with a peak torque of 200 Nm/litre at 2000-2500 rev/min. HC emissions were maintained in the range 3-15 g/kWh over the majority of the engine operating range and NOx emissions in the load range used in the FTP drive cycle were less than 3 g/kWh. Part load fuel consumption under steady state conditions was 8% lower than for a stoichiometric four-stroke engine sized for equal power output.

Computational Fluid Dynamics (CFD) simulation has been used to investigate the fuel air mixing regimes of an open chamber gasoline direct injection (GDI) engine. Acceptable homogeneous stoichiometric charge operation was predicted by the CFD simulation and confirmed by data from engine experiments with early injection timing. The simulation also predicted that late injection timing would be inoperable with the open chamber geometry employed. This was confirmed by injection timing experiments on the test engine. Subsequent initial engine development using a different engine geometry with top-entry inlet ports and a piston containing a spherical bowl has demonstrated very stable combustion with an unthrottled late injection strategy. The use of recycled exhaust gas (EGR) is demonstrated to produce better emissions and fuel consumption than purely lean operation. The effect of throttling is found to provide emissions improvements at the expense of fuel economy.