In 2007 the English company Ilmor Engineering Ltd., which has an excellent reputation in motor racing circles, built a 1,478 cc test bed engine operating on this 5-stroke concept (Ilmor 5-stroke engine). On the test bed a power output of 130 hp was measured at 7000 rpm, as was a torque of 166 Nm at 5000 rpm, and a fuel consumption of 226 g/kWh. Although the combustion processes in the two high-pressure cylinders did not correspond to state-of-the-art technology while the first measurements were being taken, the levels of consumption achieved were promising.

Here you can find the results from the first test bed measurements.

Towards the end of 1999, before the contract was signed with Ilmor Engineering Ltd., the latter had analysed the 5-stroke concept.

A report in German is available here as a PDF file (courtesy of Mercedes-Benz HighPerformanceEngines Ltd., the legal successors to Ilmor Engineering Ltd.).

This study was carried out by Dr. Hans Alten, an Ilmor employee and a recognised expert on gas-exchange analysis, in collaboration with the inventor Gerhard Schmitz, using the gas-exchange computer program Boost developed by AVL. Note that this theoretical investigation predicted a fantastic specific fuel consumption of 200 g/kWh at 4000 rpm for the 5-stroke engine fitted with a "standard inlet manifold injection system". This value was later approximately confirmed in a simulation using the gas-exchange computer program GT-Power. In the light of these predictions, it is not surprising that the very first 5-stroke prototype, as already stated above, achieved a specific consumption of 226 g/kWh on the test bed from a standing start, so to speak.

Since the spring of 2008 Ilmor Engineering Ltd. has been continuing to develop the 5-stroke engine without the involvement of the inventor, Gerhard Schmitz. A 5-stroke engine that can be installed in a vehicle has been promised for a long time.


From mid-2008, a German car manufacturer has also been developing a test bed engine based on the 5-stroke concept. This manufacturer calls this concept “extended exhaust gas expansion”. The inventor, Gerhard Schmitz, was acting in a consultative role to the car manufacturer on this development and the GT-Power simulation. The GT-Power simulation predicts a consumption of just 204 g/kWh (capacity: 2,000 cc, power output: 244 hp at 6,500 rpm, torque: 265 Nm at 6,000 rpm).

From the spring of 2009 onwards the values determined from the simulation have been verified on the test bed. At this point in time the participation of the inventor, Gerhard Schmitz, was dispensed with, and no further data or measurements have been communicated to him. From this one can assume that the simulated values have been confirmed on the test bed, and that this car manufacturer is continuing to develop the 5-stroke concept in secrecy and is working towards a technological breakthrough.

Earlier improvements in consumption on the classic Otto-cycle engine have always taken place in small percentage steps.

A concept that promises an improvement in consumption of well over ten per cent is viewed by the car industry as unrealistic and not to be taken seriously.

Also no previous improvements in consumption have been based on a modification to the basic principle of the Otto-cycle engine – the 4-stroke principle.

The idea of an extended expansion is not new and was already in existence more than fifty years ago. It is solely the combination of extended expansion and high-pressure charging that is responsible for the success of the 5-stroke concept.

To convince the automotive industry of the feasibility of the 5-stroke concept, the inventor must himself build a 5-stroke engine, demonstrate a vehicle with this type of engine, and must have access to all relevant data.

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