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Lotus tests a two-stroke engine

Lotus' Omnivore engine produces 10 percent better fuel economy than current production engines.

Lotus Omnivore engine
This development engine doesn't need spark plugs or a head gasket. Lotus

Last year, Lotus announced the development of its Omnivore engine, the name denoting flex-fuel capability. Today Lotus released test results for the engine, along with the kind of detail on how it operates only an engineer could love. These test results cover the first phase of testing the Omnivore engine with gasoline. Presumably, testing with fuels derived from alcohol and other sources are in the next phases.

In Lotus' lab, the Omnivore engine brought in 10 percent better fuel economy than current direct-injection engines, which are the most efficient on the market.

Similar to the generator engine built for hybrids Lotus announced last September, the Omnivore engine is a monoblock design, with the head cast as part of the engine block. Pushing the engineering envelope even further, the Omnivore uses homogenous charge compression ignition (HCCI), meaning that instead of igniting its fuel charge with a spark plug, the compression of the cylinder causes the charge to ignite, similar to a diesel engine. Lotus managed to get HCCI working at engine speeds below 2,000 rpm and in cold start conditions.

Omnivore also uses a two-stroke, rather than a four-stroke cycle, but it still manages to turn in emission levels equivalent to modern production engines.

Part of the engine's efficiency comes with its variable compression mechanism, what Lotus calls a puck at the top of the cylinder that dynamically changes the displacement depending on running conditions.

Omnivore is currently being run as a research engine at Lotus, with no automotive application. As such, it is a single-cylinder, 500 cc engine, making any guesses to actual fuel economy speculative.