Schaeffler and Porsche recently presented the result of a powertrain friction-reduction project, the CO2ncept-10 per cent vehicle, at the ATZ/MTZ Congress in Esslingen, Germany.

The development project involved the use of novel, optimised engine components that, when combined, achieve a 10 per cent reduction in fuel consumption and CO2 emissions.

CO2ncept-10 per cent is a CO2 demonstration vehicle based on a Porsche Cayenne with a V8 engine.

In addition to tried and tested optimised engine components, the vehicle is also equipped with several new powertrain and chassis components supplied by Schaeffler.

These components can reduce the car's fuel consumption compared with existing production models.

In the joint-development project, Schaeffler was responsible for the design and testing of components, while Porsche managed system co-ordination and validation for the entire vehicle.

The reductions in fuel consumption and CO2 emissions were verified theoretically through complex simulation calculations at Schaeffler and practically via extensive bench testing at Porsche.

The Standardised New European Driving Cycle (NEDC) was the calculation standard used.

The engine accounts for 5.8 per cent of the optimised fuel consumption and associated CO2 emissions.

Most of this (4.1 per cent) comes from modification of the Variocam Plus valve-control system, by replacing hydraulic cam timers with electro-mechanical equivalents, as well as the use of optimised switching tappets on the intake side.

An extra 1.7 per cent reduction can be achieved through minimising frictional losses, by cross-system optimisation of valve train, belt drive and chain-drive components.

Schaeffler's double-row angular-contact ball bearings, which are installed in the front and rear-axle differentials, generated a further 1.1 per cent in fuel savings.

These Twintandem bearings, which replaced the existing tapered roller bearings, significantly reduce frictional resistance when compared with conventional transmission systems.

This reduction amounts to 35 per cent in the front-axle transmission and 42 per cent in the rear-axle transmission.

Fuel consumption can also be reduced via the chassis.

Replacing the hydraulic-roll stabiliser with an electro-mechanically controlled equivalent and using smooth running-wheel bearings help to achieve a 3.2 per cent reduction in fuel consumption.

Dr Robert Plank, manager of corporate engineering at Schaeffler, said: 'As is the case with cam timers, electrically operated components make such an important contribution because they only require energy when they are operating.

'In hydraulically controlled systems, the pumps need to maintain pressure at all times, resulting in much higher energy requirements.

'This project is a good example of successful co-operation between an automobile manufacturer and supplier.

'This co-operation reduces development times, avoids extensive redundancies and makes an important contribution to competitive ability,' added Plank.

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