Thursday, August 14, 2008

Why I love Lotus redux

Probably of interest to engineering geeks only but once again I've fallen under the spell of Lotus Engineering. When they aren't out tending the hemp field they are inside designing for the future; always with the idea that less is more. Want the most efficient crossover powerplant for the near term? How about an engine that will run efficiently on any combustible liquid you pour in the tank? All it takes is a willingness to stand at least three fixed assumptions about internal combustion engines on their heads!

This article courtesy of Jalopnik via Automobile Magazine.

Lotus Engineering is starting up a project they're calling "Omnivore," a task which, if successful, could see traditional internal combustion engines go the way of the dodo. Lotus is planning to meld the two-cycle engine with new technologies — direct injection and a variable compression ratio — to create an engine able to run on almost any fuel. If you've ever wondered what the future of the internal combustion looked like, you're getting a peek now. Put your propeller cap on and join us for a pocket protector talk after the jump.

Used to be that a gas engine was a gas engine and a diesel was a diesel. With the advent of reliable direct injection, variable displacement cylinder heads that don't turn into grenades, and incredibly sensitive monitoring and control systems, it's now possible to run an engine in ways would have never worked in the past. Consider the main barrier to high-compression gasoline engines in the past — preignition. High octane numbers were a band-aid for that problem, but that also caused fuel economy to plummet. Direct injection virtually eliminates the issue, allowing engineers to put the fuel right into the chamber exactly when it's needed, high pressure be damned. It's even conceivable to run a gasoline engine on the diesel cycle with direct injection.

Now add the idea of operating with a two-cycle engine to the mix and things get really weird. Two-strokes are traditionally dirty, dirty engines to run. The huge amount of fuel used and inelegant combustion leads to lots of pollution but huge amounts of power, since you've got twice as many power strokes compared to a four-stroke. However, a two-stroke with direct injection and a variable compression ratio would be able to burn almost anything under super-high compression ratios, resulting in temperatures and pressures sufficient to completely burn almost any fuel. Of course, that assumes you can build powerful enough injectors and internal components that don't turn into Swiss cheese in extreme conditions. Let's just say this: Lotus is setting out on a path that's going to get a lot of powertrain engineering PhD's hot and bothered. If they succeed, future car engines will shrink and be more powerful as a result.

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