Diagram showing the operation of a 5-stroke SI engine. Labels:
1 – Induction
2 – Compression
3 – Power
4 – Exhaust
5 – Reuse
For a five-stroke engine, in step 5, the brown exhaust gas is fed to a non ignition cylinder from two primary.

The five-stroke engine is a compound internal combustion engine patented by Gerhard Schmitz in 2000.[1] Schmitz's concept is being developed by Ilmor Engineering. Ilmor's prototype is an internal combustion engine that 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. In order to increase efficiency, a secondary cylinder is added as an expansion processor to extract more energy from the fuel.

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.

It is a usage of Exhaust Gas from two primary Cylinder which shift to one secondary cylinder which is non ignition. Because the volume of gases reduced to half in primary cylinders after combustion.

The operation of a 5-stroke SI engine.
1 – Induction
2 – Compression
3 – Power
4 – Initial Exhaust/Re-expansion
5 – Final Exhaust

The low pressure expansion cylinder is adjustable to maintain the best expansion ratio, regardless of the compression ratio. The prototype has produced very good fuel consumption over a standard gas engine, by about 10%.[2][3][4][5][6]

This concept is similar to that of compound steam engines, which expand steam in high pressure cylinders before exhausting it into low-pressure cylinders in order to extract more energy from the steam. Nicolaus Otto built in 1879 a 5-stroke engine with same arrangement as Ilmor, but customers returned it due to poor performance. 'The romance of engines', T Suzuki, SAE, pp 87–93.[7] Two Spanish patents, ES0156621, F Jimeno-Cataneo, 1942; and ES0433850, C Ubierna-Laciana, 1975; describe 5-Stroke engines identical to that of Gerhard Schmitz, this engine had a fellowship to Burgundy University to be studied. JW Eisenhuth patented, US640890, 1900, an 'Air and gas engine', with double expansion. A car with this engine was in exhibition in Harrah collection, fate of car after the collection was dismantled is unknown.


A planned motorcycle design from Ilmor Engineering 1,478 cc totally 3 cylinder (HP and LP cylinders) uses a five-stroke engine.[citation needed]




See also


  1. ^ Google Patents, Five-stroke internal combustion engine, US 6553977 B2, filled Oct 26, 2001
  2. ^ Ilmor, 5 Stroke Engine
  3. ^ Five stroke engine animation
  4. ^ 5-stroke-engine.com, The five-stroke concept – ingeniously simple, simply ingenious
  5. ^ autoevolution.com, Five-Stroke Engine Works and Might Enter Production. 26 Sep 2014, by Gabriel Brindusescu
  6. ^ Ilmor 5 Stroke Engine – 700cc Turbo 3 Cylinder – 130 bhp, Better Mileage, Less Weight, By Paul Crowe
  7. ^ Suzuki, Takashi (May 1997). "The Romance of Engines": 87–93. doi:10.4271/r-188. ((cite journal)): Cite journal requires |journal= (help)