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Method and apparatus for controlling emissions, particularly of unburnt hydrocarbons, from a two stroke engine. The engine has direct in-cylinder fuel injection and has in the air inlet port and the exhaust port respective devices to control the flow therethrough. The devices are each independently

Method and apparatus for controlling emissions, particularly of unburnt hydrocarbons, from a two stroke engine. The engine has direct in-cylinder fuel injection and has in the air inlet port and the exhaust port respective devices to control the flow therethrough. The devices are each independently controlled in relation to engine load demand and engine speed to regulate the mass of exhaust gases retained in the combustion chamber. The exhaust flow control device perferably also alters the timing of opening and closing of the exhaust port.

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A method of operating an internal combustion engine on the two stroke cycle to control the level of contaminants in the exhaust gases, the engine having a cylinder, a piston mounted to reciprocate in the cylinder, said piston and cylinder defining a combustion chamber that cyclically varies in volum

A method of operating an internal combustion engine on the two stroke cycle to control the level of contaminants in the exhaust gases, the engine having a cylinder, a piston mounted to reciprocate in the cylinder, said piston and cylinder defining a combustion chamber that cyclically varies in volume as the piston reciprocates, an air inlet port providing communication between the combustion chamber and a source of air, and an exhaust port providing communication between the combustion chamber and an exhaust duct, said inlet and exhaust ports being arranged to be opened and closed by the piston as it reciprocates in the cylinder, said method comprising admitting a charge of air to the combustion chamber through the inlet port, compressing the charge of air in the combustion chamber by the movement of the piston after the inlet and exhaust ports have been closed, injecting a metered quantity of fuel into the air charge in the combustion chamber, igniting said fuel charge, and exhausting the products of combustion through the exhaust port after expansion in the combustion chamber, sensing the engine load demand and engine speed while the engine is operating, and regulating the mass of the products of combustion retained in the combustion chamber at closure of the ports so hydrocarbons present in the exhausted products of combustion are in predetermined limits by controlling the flow of gases through the exhaust port while open in relation to engine speed and load to provide a plurality of predetermined rates of gas flow in the combustion chamber over the full range of engine speeds and loads, said controlling including adjusting the degree of throttling of the exhaust port through a range of values between a minimum and a maximum, said degree of throttling of the exhaust port being preset in relation to engine load and speed.