Our objective with the 5-stroke engine is to develop a gasoline engine with fuel consumption and emission levels comparable to that of current diesel engines, without the serious problem of particulate and NOx emissions that plague diesels.
The engine concept, which was invented by Gerhard Schmitz, has been developed by Ilmor into a working engine using a rapid prototype cast cylinder head, a machined from solid cylinder block and separate electrically powered oil and water pumps. Two overhead camshafts operate the conventional coil spring valvegear with the HP camshaft running at 0.5 x crank speed and the LP camshaft running at 1 x crank speed. The engine is also turbocharged to increase the engine rating.
The 5-stroke concept engine utilises two fired cylinders (High Pressure - HP) operating on a conventional 4-stroke cycle which alternately exhaust into a central expansion cylinder (Low Pressure - LP), whereupon the burnt gases perform further work. The LP cylinder decouples the expansion and compression processes and enables the optimum expansion ratio to be selected independently of the compression ratio.
Running of the concept engine has produced impressive fuel consumption readings over a very wide operating range. This is because at the onset of knock a greater percentage of work can be extracted in the LP cylinder, giving a degree of self compensation.