Controlled self-ignition combustion process and four cycle engine with transfer conduits between exhaust and intake conduit

The control procedure, for use on a multi-cylinder 4-stroke engine with each cylinder (1) having at least one inlet (2) and exhaust (3) duct, consists of taking a quantity of the exhaust gas from one cylinder when the engine is under partial load and transferring it to the inlet duct of another via valves (4, 7). During the transfer the gas can be thermally insulated and/or reheated by catalysis in a common transfer duct (5). At the same time as the gas is heated, the catalyst (10) can be used to reduce the pollutants in it.