Five-stroke engine

Five-stroke engine is currently a concept engine invented by Gerhard Schmitz in 2000.[1] Schmitz's concept is being developed by Ilmor Engineering. Ilmor's prototype is an internal combustion engine uses a solid cylinder block with electric motors driving the oil and water cooling pumps. The prototype uses two overhead camshafts with standard poppet valves. The Five-stroke prototype engine is turbocharged. The goal of the five-stroke engine is to have higher efficiency with lower fuel use. To increase efficiency a secondary cylinder is added as an expansion processor to extract more energy from the fuel.

Diagram showing the operation of a 4-stroke SI engine. Labels:
1 ‐ Induction
2 ‐ Compression
3 ‐ Power
4 ‐ Exhaust
For a Five-stroke engine, in step 4 the brown exhaust gas is fed to a larger low pressure cylinder

Gerhard Schmitz's concept engine uses two high pressure (HP) fired cylinders with standard four-stroke engine power cycles. The exhaust gas from the two HP work cylinders is fed into a one larger central low pressure (LP) expansion cylinder. The hot exhaust is used to produce more power. The low pressure expansion cylinder is adjustable to maintain the best expansion ratio, regardless of the compression ratio. Prototype has produced very good fuel consumption over a standard gas engine, by about 10%.[2][3][4][5][6]