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.

Gerhard Schmitz’s concept engine uses two high power (HP) fired cylinders with standard four-stroke engine power cycles. The exhaust gasfrom 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]

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


  • For a gasoline engine, the engine has an expansion ratio near that of diesel engine, about 14.5:1.
  • Adjustable compression.
  • Higher mean effective pressure with less fuel, due to expansion cylinder.
  • Use standard engine parts, no special one of a kind parts.


  • Increased costs due unique design. Not mass-produced yet.
  • Two different cylinder sizes.
  • More complex than 2 cylinder engine.


  • Current prototype is for motorcycle use.
  • 3 cylinder (two high power and one low power)
  • 700 cc 2 HP cylinder
  • 1478cc total 3 cylinders (HP and LP)
  • 130 horsepower @ 7000rpm
  • 166Nm @ 5000rpm
  • 226g/kWh BSFC


  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., The five-stroke concept – ingeniously simple, simply ingenious
  5., 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
Crankpin A crankpin or crank journal is a journal in an engine or mechanical device. That is, the part of a shaft or axle that rests on bearings. In a reciprocating engine, the crankpin is the part of a crankshaft where the lower end of a connecting rod attaches. In a beam engine, a single crankpin is mounted on the flywheel; In a steam locomotive, crankpins are often mounted directly on the driving wheels.  Crankpins highlighted in blue A crankpin of a ship steam engine with the lubricating system visible Application A crankpin is separated from its shaft or axle by a bearing. These are commonly bushings or plain bearings, but less commonly may be roller bearings. In a multi-cylinder engine, a crankpin can serve one or many cylinders, for example: In a in-line or opposed engine, each crankpin normally serves just one cylinder. In a V engine, each crankpin may serves one or two cylinders, depending on the design. In a radial engine, each ...
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Motor oil Motor oil, engine oil, or engine lubricant is any of various substances comprising base oils enhanced with additives, particularly antiwear additive plus detergents, dispersants and, for multi-grade oils viscosity index improvers. In addition to that, almost all lubricating oils contain corrosion (GB: rust) and oxidation inhibitors. Motor oil is used for lubrication of internal combustion engines. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge (one of the functions of dispersants) and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves sealing of piston rings, and cools the engine by carrying heat away from moving parts. Motor oils today are blended using base oils composed of petroleum-based hydrocarbons, that means organic compounds consisting of carbon and hydrogen, or polyalphaolefins (PAO) or their mixtures in various proportions, so...