Better known for its sportscars and pending re-entry to F1, Lotus, via its engineering arm, has debuted a purpose-built range-extending petrol powerplant.

The company has calibrated the 1.2 litre, three-cylinder aluminium engine at the heart of the unit for twofold application: its integrated power generator allows it to power the electric motor directly, or it can provide continuous charge to a battery pack.

The engine design hails in large part from the company's engineering division's research into the burgeoning hybrid market, which showed that a high-efficiency, low-mass range extender engine would help reduce the cost burden for auto makers engaged in the costly business of power pack development, namely cutting battery mass and improving energy density.

The unit serves up 15kW of electrical power at 1500rpm direct and 35kW at 3500rpm via an integrated electrical generator running direct off the crankshaft.

The engine's monoblock design integrates the cylinder block, cylinder-head and exhaust manifold in a single casting with simple two-valve port fuel-injection to keep to keep engine mass down to 56kg and cut manufacturing costs.

To help keep it clean, it's flexfuel-ready, capable of running on any mix of petrol and ethanol. At the other end, a close-coupled catalytic converter minimises heat loss in the transfer of exhaust gases through the manifold to the catalyst inlet. The result is faster light-off in the converter, helping minimise toxic emissions.

The engine forms part of the UK's 'Limo Green' project, a joint venture including Lotus and Jaguar and using funding from Britain's Technology Strategy Board to come up with a high-end exec express emitting less than 120 g/km of CO2.

"Most series hybrid vehicles that are currently being developed will use adaptations of existing, conventional engines," Simon Wood, Technical Director of Lotus Engineering told media in a statement.

"So they're therefore compromised in the efficiency they can achieve, designed as they are for a wide range of operating conditions. Designing this engine purely for use in series hybrids has allowed us to optimise it for high thermal efficiency, low fuel consumption, multi-fuel capability and a 35kW peak output from a 1.2-litre, low-cost architecture over the precise operating range required by a series hybrid drivetrain."

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