American carmakers have built flex-fuel engines capable of running of ethanol blends and gasoline for years now, but the alternative fuels haven't caught on and efficiency is often compromised at both ends to allow for that flexibility. The idea behind the Omnivore engine from Lotus Engineering is to use a variable compression ratio and a two-stroke operating cycle. On top of those techniques, they add direct injection for precise fuel metering and even more efficiency.
One unique element of the variable compression design is a cylinder head and block that blend together, eliminating the need for a gasket between the two. The compression ratio is varied by a puck at the top of the combustion chamber, which can adjust compression dynamically based on engine load.
The Omnivore project was first revealed last year as a joint project with Jaguar. The statement on the program released today contained no mention of Jaguar, however, so it's not clear if the Leaping Cat is still involved with the experiment.
A similar proof-of-concept vehicle, the Lotus 270E, demonstrated the flexibility of fuel use, if not the advanced technology and high efficiency of the Omnivore engine. Due to some of the complications arising from introducing variable compression ratio technology into four-stroke engines, however, don't expect to see a Lotus 270 Omnivore any time soon.
The ongoing debate over the sustainability and 'greenness' of alcohol-based fuels is also another potential hurdle, though if projects like those being undertaken by Coskata and the like bear fruit, things could work out well for Omnivore.