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.

Principle of operation

The 5-stroke concept engine utilizes 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.

Further development

Having run the proof of concept engine, Ilmor is now looking to produce a second phase development engine for in-vehicle testing. The performance targets for this engine are as follows:

• Brake Specific Fuel Consumption of 215 g/kWh
  (10% improvement on current 4 stroke technology)

• 20% lighter than existing production engines

• Power density of 150 bhp/L

Advantages of the 5-stroke concept

• A secondary cylinder provides an additional expansion process enabling extra work to be extracted, hence increasing thermodynamic efficiency.

• The engine runs an overall expansion ratio approaching that of a diesel engine – in the region of 14.5:1

• Minimised pumping work due to the downsizing effect from highly rated firing cylinders.

• The compression ratio can be reduced to delay knock onset without a reduction in performance.

• Because the firing cylinders can be very highly rated, the engine is relatively compact.

• The fuel consumption does not rise as rapidly with increasing BMEP, as retarding rejects more energy into the expansion cylinder.

• The engine uses 100% conventional technology and so requires no new manufacturing techniques.

5-stroke performance figures

• Engine capacity 700cc (turbocharged)

• Peak power 130 bhp @ 7000 rpm

• Peak torque 166 Nm @ 5000 rpm

• Fuel consumption of only 226 g/kWh

Ilmor is using its race engine expertise to bring developments to the field of energy efficient engines. Motor racing is not generally associated with fuel economy, but the lessons learned during periods of intense engine development can be applied with great effect to create highly fuel efficient engines.

Fuel efficiency can be improved by downsizing engines – creating the same amount of power from a smaller swept volume (smaller capacity) which typically burns a smaller amount of fuel. High performance engine design is all about extracting as much power as possible from a defined capacity by the use of intelligent design, low friction coatings or even completely new concepts. All of this knowledge can therefore be applied to maximise the power output of a small capacity, fuel efficient engine.

Our flexible approach ensures that we are able to build on a concept and develop innovative, tailored and most importantly working solutions for our clients, allowing physical testing and ongoing development of the concept.

• Designs to customer specification

• Cost effective solutions

• Rapid manufacture / Rapid prototype / Short lead time

• Sub system or complete engine

5-stroke concept engine

One such example of this application of our engineering knowledge is the patented 5-stroke engine which Ilmor is currently developing. 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 simplest way to demonstrate the 5-stroke principle was considered to be a 3 cylinder layout with two fired 4-stroke cylinders (High Pressure – HP) alternately exhausting into a central expansion cylinder (Low Pressure – LP) which provides a further expansion process on the exhaust gases (the 5th stroke).

The engine uses 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.

Reference: www.ilmor.co.uk