| 摘要 |
A spark ignition internal combustion engine having an exhaust emission control system including an air pump driven by the engine to pump fresh air directly into the exhaust duct in order to promote a further combustion of partly burnt components in the gases coming from the combustion chambers, excess air pressure being released by a pressure relief valve into an air filter for the induction air; the system also comprises an exhaust gas recirculating system comprising a pneumatic valve which opens, when the conditions are appropriate, to draw off a proportion of the exhaust gases from the exhaust side of the engine and admit them to the induction side of the engine; in addition there is a system for admitting supplementary air to the induction manifold downstream of the carburettor during engine overrun conditions except when the engine is cold, and the carburettor is provided with supplementary pumps and valves which only function when the engine is cold, being inhibited as the engine approaches its normal working temperature. |
