Lotus Range Extender Engine

Lotus Engineering is bringing an all new engine to the Frankfurt Auto Show. The new engine was specifically designed to be used in an extended range electric vehicle (E-REV).

You can think of E-REV as a plug-in electric vehicle with a built in gas motor used not to move the car, but to recharge the battery when it gets low. This extends the range the electric vehicle can go on one charge.

The Chevy Volt, for instance, will be able to travel 40 miles on all electric power after being plugged in (overnight). Once the battery gets low, the gas engine will kick in to keep the battery charged until you can plug the vehicle in once again.

The Lotus Range Extender engine is a three cylinder 1.2 litre capable of producing 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm via the integrated electrical generator. The aluminium monoblock construction, integrates the cylinder block, cylinder head and exhaust manifold in one casting. This results in reduced engine mass (56 kg), assembly costs, package size and improved emissions and engine durability.

The engine uses a two-valve port-fuel injection combustion system which reduces cost and mass. It can also be used with alcohol based fuels.

The Lotus Range Extender engine reduces cost in design and mass, allowing for the inclusion of the large (and heavy!) battery packs necessary in an E-REV. Lotus expects the engine offers a fast route to market for original equipment manufacturers wanting to source a dedicated range extender for series hybrid vehicles.


Technical details:
Technical specification of the Lotus Range Extender engine

General - 1.2 litre 3-cylinder with 2 valves per cylinder, SOHC
Belt driven
Construction - Monoblock with Integrated Exhaust Manifold
All aluminium
Balance shaft (optional)
Direct-coupled generator
Bore and Stroke - 75.0 mm x 90.0 mm
Compression ratio - 10:1
Maximum power - 35 kW (47 bhp) at 3500 rpm via integrated electrical generator
Peak torque - 107 Nm at 2500 rpm
Maximum BMEP - 11.2 bar
Maximum Engine Speed - 3500 rpm
Fuel System - Port fuel injection, Lotus EMS
Fuel - 95 RON ULG / ethanol / methanol
Dry weight - 56 kg

Key features of the Range Extender engine in detail:
Monoblock
The Range Extender features a novel engine architecture incorporating a monoblock construction that blends the cylinder head and block together eliminating the need for a cylinder head gasket, improving durability and reducing weight. Approximately 17 parts are eliminated using this approach and the water jacket is better optimised.

Integrated Exhaust Manifold
Lotus Engineering designed and developed a new advanced cylinder head design featuring an integrated exhaust manifold. The production-ready technology can significantly reduce manufacturing costs, emissions and weight. An integrated exhaust manifold has potential to:
o Reduce parts count: 18 fewer components resulting in lower inventory, production, logistics and aftermarket costs
o Weight reduction: total system mass reduction resulting from elimination of separate exhaust manifold
Improved engine durability


Generator
Attached to the engine via the crankshaft, the generator sustains vehicle operation beyond the range provided by the batteries.

Additional Benefits
The Lotus Range Extender engine generates a reduction in emissions through faster light-off of the close-coupled catalytic converter with a reduction in heat loss between the exhaust port and catalyst inlet. Engine operating range is optimised to deliver more efficient running, which also aids underhood thermal management.

Utilisation of the monoblock construction results in an assembly cost reduction, while there is also a reduced catalyst loading requirement because less heat is lost on engine start-up between the exhaust port and catalyst inlet.

Increased vehicle integration flexibility is achieved because of the reduction in mass and the reduced package size leads to reduced space requirements. Particular emphasis has also been placed on the coupling of the generator and NVH signature.