Internal combustion engine with exhaust emission control system

摘要

A four cylinder spark ignition internal combustion engine has an exhaust emission control system including means for admitting fresh air into the exhaust system in order to promote a further combustion of partly burnt components in the gases coming from the combustion chambers, this means include a "reed" valve connected to the exhaust ports leading from the first and fourth cylinders (numbering from one end of the engine) through internal passages within the cylinder head; 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 taking exhaust gases from branches of the exhaust manifold carrying exhaust gases from the second and third cylinders; 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.