Ilmor Engineering 5-stroke engineEnlarge Photo
Now, an engineering firm by the name of Ilmor has announced its own new redesign of the internal-combustion engine, with claims that efficiency gains of between 5% and 20% can be had. What makes us actually sit up and take notice of Ilmor's claims is the company's history, having built Formula 1-winning engines for Mercedes-Benz and working with a number of Indy car teams for over a decade to build engines - not exactly amateurs, then.
The new, more efficient engine Ilmor is proposing promises to deliver the fuel economy that current diesel engines can achieve, without the associated emissions problems the oil-burners typically offer. Designed for road cars, rather than its usual work with racing applications, the Ilmor-designed 5-stroke gasoline engine is a diminutive 700cc three-cylinder unit that still manages to develop 130 horsepower and 122 pound-feet of torque.
According to Ilmor, the 5-stroke concept engine utilizes two high-pressure fired cylinders operating on a conventional 4-stroke cycle that alternately exhaust into a central low-pressure expansion cylinder, whereupon the burnt gases perform further work. The low-pressure cylinder decouples the expansion and compression processes and enables the optimum expansion ratio to be selected independently of the compression ratio.
The end result is that the engine runs an overall expansion ratio approaching that of a diesel engine – in the region of 14.5:1. The engine is also more compact, and unlike other new technologies does not require any new manufacturing techniques. The engine is just a concept for now, with further development expected to take place. Eventually, the company hopes to achieve a power density figure of 150 horsepower per liter of displacement.