Ilmor Engineering Creates Experimental Five-Stroke Engine

By KBB.com Editors on August 11, 2009 11:54 AM

Famed race-engine design house, Ilmor Engineering, has shown an innovative take on the conventional gasoline engine that incorporates a unique fifth stroke to its operating cycle. It's a twist that Ilmor claims can add 5-20 percent more efficiency while using 100 percent of today's existing technology. The test engine is a 700cc turbocharged inline three-cylinder with two normally configured high-pressure cylinders flanking a low-pressure center cylinder that is activated by pressures from the spent exhaust gases. Ilmor says that by decoupling the compression/expansion processes, the engine can operate in a near-diesel type of environment, creating an effective compression ratio of 14.5:1 while benefitting from significant reductions in pumping losses. At this stage in the development process, the five-stroke engine is turning out 130 horsepower -- which works out to a heady 169 horses per liter -- and 122 lb.-ft of torque. The next phase calls for an additional 10 percent improvement in fuel efficiency, bumping output to 201 horsepower per liter and creating a package that will be 20 percent lighter than an equivalent production engine. Although Ilmor admits there's a good deal to be done before the engine will be ready for production, it's worth remembering that among its legion of notable engine accomplishments are several Formula One engines in the early '90s, the stunningly successful stock block "pushrod" Indy Car engines that alternately saw victory wearing both Chevrolet and M-B badging during that same period, and co-development credit (with Honda Performance Division) for the V8 currently used by the Indy Racing League.

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