| Lotus Engineering has fitted a mild hybrid and a downsized engine in an Opel Astra to demonstrate how OEMs could cut CO2 by 2012 – without sacrificing performance. The prototype uses production-ready technology.
The prototype is a five-door model fitted with a 1.5-litre three-cylinder gasoline engine, a mild-hybrid system and a six-speed gearbox. It produces 118kW (158hp) power, 240Nm torque and 149g/km CO2.
It outperforms a naturally aspirated 1.8-litre Astra, which produces 103kW (138hp) power, 175Nm torque and 175g/km CO2.
Lotus chief executive Mike Kimberley said: “We used proven technologies that are ready to go into the next model generation to deliver a car that engages keen motorists, but has a lower impact on the environment.”
The engine was built with Siemens VDO. After Continental’s purchase of VDO last year, the project changed only slightly.
The engine mounts the solenoid injectors centrally instead of on the side. They are close to the spark plug, but offset from the valves by slightly different distances. This lets valve deactivation control the combustion more carefully, but can cause the injectors to coke. Lotus said the chamber design prevents this and is investigating. The solution is usually to use expensive piezo injectors.
Despite Continental’s plans to launch a mechatronic unit, the engine uses a conventional turbo. It integrates the exhaust manifold into the head to reduce weight and improve catalyst light-off times. It also uses Lotus/INA’s lobed tappets that vary valve lift and timing. Electric water and fuel pumps improved efficiency by 2 per cent.
Changes to the engine account for half of the fuel economy improvements. Fuel economy is helped by the use of a 12kW mild-hybrid system – switching off the engine when the car comes to rest and recovering brake energy in 60V supercapacitors.
Continental will fit low-rolling resistance tyres to increase economy further.
© Automotive Engineer, 2008
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