From Lotus Engineering, the consulting arm of the automaker, comes a concept for an engine to be used as a range extender on series hybrid cars. The new design maximizes efficiency for an engine that will only function as a generator.
Series hybrid cars, such as the upcoming Chevy Volt, use electric motors to drive the wheels, with electricity sourced from a battery pack and generator. This type of car operates as a pure electric vehicle up to the maximum range afforded by its batteries, typically under 100 miles with current technology. To go further, an onboard generator produces electricity to drive the motors. Although some concepts have used fuel cells to generate this additional electricity, the first production series hybrid car will likely use a small gasoline engine.
Lotus points out that most engines proposed for series hybrid cars are existing car engines retuned for electricity generation. The Lotus engine has been designed from the ground-up for its purpose. The design was greatly simplified by casting the engine block, cylinder heads, and exhaust manifold as one piece, making production less costly and eliminating the need for some parts, such as the head gasket, which require regular maintenance.
The three cylinder engine displaces 1.2-liters and only uses two valves per cylinder, actuated by a belt-driven single overhead cam. The design includes a generator directly coupled to the engine. The engine can operate in two modes, with outputs of 15 kilowatts or 35 kilowatts. Lotus doesn't mention fuel consumption, a number that wouldn't be particularly relevant anyway without information what sort of car it would be mounted in.