2009 Frankfurt Auto Show Preview: Lotus Range Extender Engine for Hybrids

HETHEL, England — Lotus Engineering has developed a new engine specially designed for use in range-extending series hybrids. The 1.2-liter three-cylinder power unit is designed for maximum efficiency and can be used to recharge the batteries of a range-extender hybrid as well as to drive the electric motor directly.

Alternatively, the battery can power the electric motor, offering a range of propulsion choices to suit differing emissions, range and performance requirements.

The engine itself is unusual for being a three-cylinder aluminum monoblock with the cylinder head, block and exhaust manifold cast in one piece. This reduces weight, bulk and complexity as well as improving emissions and durability. The engine is also cheaper to make. Lotus's aim was to partly offset the high cost of a hybrid's batteries, while the Lotus product's inherent efficiency and low weight should also allow for a smaller battery pack.

The engine is optimized to suit two power generation speeds of 1500 rpm and 3500 rpm, at which revs it produces 20 and 47 horsepower, respectively. The engine's maximum revs are 3500 rpm, and it produces 79 pound-feet of peak torque at 2500 rpm. Its two-valve-per-cylinder single-cam design reduces weight and cost, and it can run on a variety of renewable fuels.

Inside Line says: Lotus Engineering has a history of developing powertrains for third parties, and this intelligent powertrain could win customers. — Richard Bremner, Correspondent