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A low pressure pneumatic direct injection engine by AR Combustion concept has been developed. In this engine, the scavenging process is performed by air only, prior to the fuel feed process, which minimizes the fuel short-circuiting accompanying the scavenging flow. The wide spray form generated by the rotary type injector facilitates homogeneous combustion even in the high speed high load range, which promises higher maximum power output. Meanwhile, in the light load range, AR Combustion effectively solves the irregular combustion. The bench test results show a remarkable reduction in the exhaust emissions and fuel consumption while successfully maintaining high power output of original two-stroke engine. Moreover, actual vehicle tests using a motorcycle reveal its good potential as a vehicle engine.

From the environmental conscious point of view, subjects of conventional two-stroke engines will be irregular combustion and new mixture shortcut. Concerning for the irregular combustion, our previous papers has however proven that timing controlled auto-ignition, namely Activated Radical (AR) Combustion, was an effective solution. Meanwhile for the new mixture shortcut, no solution is mentioned in those papers. This time, a low pressure pneumatic direct fuel injection engine has been experimented. This engine is however intended to perform homogeneous combustion, the A R Combustion solves irregular combustion effectively in the light load range. Fuel is pneumatically injected into the cylinder by using accumulated in-cylinder gas pressure, after the scavenging process performed by the air only. A mechanically driven rotary type injector is installed in the cylinder wall.

A timing controlled auto-ignition named “AR combustion” could improve irregular combustion in the part load operation of conventional two-stroke engines. Our previous papers have suggested its idea and the drastic improvements in fuel consumption and HC emission proven through a bench experiments. This time, from a concept that improvements of a two-stroke engine should be done maintaining its original advantages, an AR combustion engine was developed by using a simple exhaust valve and maintaining engine's original power output. This engine was mounted on a motorcycle and experimented in the “Dakar rally”. As the results, good fuel economies exceeding a four-stroke rally model, excellent driveability and durability were proven, because of the improvement in the combustion and engine's potential for the downsizing. The AR combustion engine, consequently, has good prospects for the practical use.