FRANCE: Renault develops 97g CO2/km Logan concept

By just-auto.com editorial team | 14 November 2007

Following on from its May launch of 'eco²' branded environment-friendly and economical cars, Renault  has developed the experimental Logan eco² concept to contest the 2007 Michelin-organised Challenge Bibendum in Shanghai, China.

The concept meets all three criteria covering production, use and recycling required to earn the eco² badge and is particularly strong in the area of CO2 emissions with a score of just 97g/km.

Forty percent of Renault's current range meets the requirements - must emit less than 140g of CO2/km or else run on biofuel, be manufactured in an ISO 14001-certified factory, be 95% end-of-life reusable, and at least 5% of the plastics used in production must be sourced from recycling.

The concept was manufactured at the Pitesti plant in Romania, which has been ISO 14001-certified since 2005, while the finished vehicle contains 8.3% of recycled plastics and is 95%-reusable by weight.

To bringing its CO2 emissions below the 100g/km threshold, the concept has Renault's familiar 1.5 dCi (63kW/85hp) engine (also used in some European Nissan models) which, in this case runs on B30 biofuel1 but the final drive ratio has been lengthened 8% to reduce fuel consumption while ensuring a level of mid-range acceleration that is suitable for ordinary use. This saves 4g of CO2/km.

The injection system has been recalibrated using seven-hole nozzles (instead of five as is the case with production models which emit 120g/km) and widening the piston bowl for enhanced fuel spray and combustion. This saves 5g of CO2/km.

Finally, by optimising the play between certain moving parts and using low-viscosity lubricants (5W20 plus additives instead of the standard 5W30), internal engine friction is reduced. The gear oil is also less viscous. This cut CO2 by a further 2g/km.

Powertrain adjustments led to a total CO2 emissions gain of 11g/km.
Testing identified six aerodynamic points for modification: a flexible splitter under the front bumper to reduce under body turbulence combined with a spare-wheel fairing to optimise the flow of air underneath the car.

Front air intakes were modified to reduce the drag caused by air-cooling airflow, wheel fairings reduce lateral turbulence and a rear lip spoiler reduces the vehicle's overall drag performance.

Vortex generators (small, drag-reducing, roof-mounted features that channel airflow to reduce rear drag, a particularly effective solution on three-box cars, were added and the ride height was lowered slightly.

All this reduced the drag coefficient by about 20%, from 0.36 for the production Logan to 0.29, a score that makes the concept one of the most aerodynamically efficient three-box sedans.

Reducing drag produced a CO2 gain of 5g/km.

The concept also has new Michelin Energy Saver 185/65R15 low rolling resistance tyres which brought a CO2 gain of 2g/km.

The use of low-friction rear bearings led to an emission gain of around 1g of CO2/km and the camber and toe settings were also optimised.

All work on the running gear made emission gains of 3g/km.

The active control alternator ensures that the battery is charged only as required (12.8 volts instead of 13.5). The battery consequently doesn't have to be charged so frequently, which leads to lower fuel consumption.
Measures taken to reduce the effect of energy-hungry parts helped reduce CO2 emissions by 4g/km.

All the work that went into the concept achieved record low CO2 emissions of just 97g/km equivalent to fuel consumption of 3.8 litres/100km.

The extra-urban phase of the NEDC driving cycle returned UTAC homologated fuel consumption of just 3.4 litres/100km, equivalent to CO2 emissions of 88g/km.

As driving style can also play a significant role when it comes to curbing fuel consumption and CO2 emissions, the car also has a gearshift indicator which enables drivers to bring the concept's CO2 emissions performance down below the homologated score of 97g/km.