Lotus Range Extender Helps Power Jaguar XJ Hybrid Sedan

A while back, Lotus Engineering, Jaguar Cars Ltd., MIRA Ltd., and Caparo Vehicle Technologies embarked on the ‘Limo-Green’ development program. Funded by the UK’s Technology Strategy Board, the program’s aim was the development of a large, lightweight, and prestigious executive sedan with CO2 emissions of less than 120 g/km.

Lotus Engineering recently unveiled the Lotus Range Extender propulsion system that would be used for the Limo-Green vehicle. Like the Chevy Volt and Fisker Karma, the range extender strategy creates a plug-in series hybrid that enables batteries to be charged off the grid, as well as by regenerative braking. The range extender’s engine is mated to a generator that can also charge the batteries while driving, thus extending driving range beyond what would be provided by battery capacity alone.

Like the Volt, a small displacement three-cylinder gasoline engine is used to drive the generator. The 1.2-liter range extender engine uses innovative aluminum monoblock construction that integrates the cylinder block, cylinder head, and exhaust manifold in a single casting. Interestingly, monoblock engines were used in the early days of the automobile. In this case, the approach results in a lightweight engine of only 123 pounds while also reducing parts count and assembly cost. Plus, eliminating the cylinder head gasket improves durability.

The belt-driven SOHC (single overhead camshaft) engine uses two valves per cylinder and a 10:1 compression ratio. It features an optimized two-valve port fuel injection system and can be run on alcohol-based fuels or gasoline. The generator is directly attached to the engine via the crankshaft and offers a maximum 47 horsepower (35 kW) at 3500 rpm. Batteries supply power to a 145 kilowatt, 295 lb-ft electric motor.

The Lotus Range Extender will be used in a series hybrid version of the all-new Jaguar XJ sedan. While the new XJ will be a 2010 model, the hybrid version will probably appear as a 2011 variant. Jaguar’s goal for the Limo-Green is an electric-only range of 30 miles with the range extender increasing this to 600 miles. This should result in a combined fuel economy of 57 mpg, CO2 emissions of less than 120 g/km, and a top speed of 112 mph … excellent credentials by any measure.