Abstract: An internal combustion engine in which the combustion mixture passing into the cylinder (4) includes a pressure pulse formed during the preceding closure of the inlet (6) so that the volume of combustion mixture passing into the combustion chamber is greater than would normally be delivered. In a particular form during the charging of the engine, part of the combustion mixtures passes through the combustion chamber to exhaust (5) and is forced back into the combustion chamber by means of a pressure pulse in the exhaust system which pulse is formed from previous combustion, thereby effectively super charging the chamber before the inlet and exhaust ports are closed and the compression effected. This is particularly suitable for two stroke engines but the invention can be applied to other engines such as four strokes and ram or scram jet engines.