While vehicle performance figures that outdo product rivals continue to be essential for market success, there is now a definite shift to a new set of credentials: low levels of CO2 per km. An example of this trend can be seen in the rivalry among manufacturers that took part in the annual Michelin-organized Bibendum Challenge green vehicle event in
To demonstrate the capability of budget-level cars to meet the challenge and achieve high efficiency, the Logan Renault eco² concept covered a 172.2-km test route in China on 4.69 L of diesel fuel for an average consumption of 2.72 L/100 km, complemented by CO2 emissions of 71 g/km. (Depending on the country of sale, Logan is commercialized under the Dacia and Renault brands.)
During the official NEDC combined cycle homologation tests for the vehicle, it achieved 97 g/km, which equated to 3.8 L/100 km. This result was improved over the route of the Bibendum Challenge thanks to the driver’s use of the car’s gearshift indicator, highlighting the importance of “eco driving” aids, according to Logan. After the event, a classification of competing vehicles was drawn up based on the following criteria: acceleration test, slalom test, noise emissions, and “regularity run.” The Logan Renault came second behind an Audi A5 TDI.
Powered by a 1.5-L dCi diesel engine producing 63 kW (84 hp), the five-seat Logan concept successfully demonstrated that it was possible to “combine ecology and economy without detracting from performance” and do so via an affordable vehicle, stated the company.
Mechanical changes to the concept compared to the production model on which it was based include a modified fuel-injection system, low-rolling-resistance Michelin tires, and aerodynamic enhancements.
But the car’s eco credentials—it can burn B30 biofuel—encompass more than just its operation. It is built at
Renault says its eco² symbol illustrates the brand’s commitment to offering a lineup of ecological, economical vehicles that show measurable environmental benefits throughout their life cycles, as well as new technologies at prices that most customers can afford. To qualify for the symbol, vehicles must emit less than 140 g of CO2 per km or 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 the vehicle’s production must be sourced from recycling. The concept contains 8.3% of recycled plastics and is 95% reusable by weight.
To get below the 100-g/km figure, the concept incorporates a raft of technical enhancements and innovations, all of which have been developed for potential incorporation in future Renault models. Its engine is based on the 1.5 dCi engine launched at the end of 2007 and homologated at 120 g CO2/km. But the concept’s final drive ratio has been raised 8% to reduce fuel consumption while ensuring a level of midrange acceleration that is suitable for ordinary use. These enhancements gave the concept a CO2 saving of 4 g/km, reported Renault.
The injection system has also been recalibrated with seven-hole nozzles (instead of five, as is the case with production models) and wider piston bowls for enhanced fuel spray and combustion. This modification produced a further savings of 5 g/km of CO2. Finally, by optimizing the balance between certain moving parts and using low-viscosity lubricants (5W-20 plus additives instead of the standard 5W-30), internal engine friction has been reduced. The gear oil is also less viscous. This work helped cut CO2 emissions by a further 2 g/km. Overall, powertrain adjustments led to a total CO2 emissions reduction of 11 g/km.
Aerodynamics always play a crucial part in supporting purely mechanical changes aimed at enhancing efficiency. Compared to the standard car on which the concept is based, Logan Renault identified six aspects that together produced significant aerodynamic gains. A flexible splitter under the front bumper reduces underbody turbulence and is combined with a spare-wheel fairing to optimize airflow under the car. The front air intakes were modified to reduce the drag caused by air-cooling airflow. Wheel fairings were fitted to reduce lateral turbulence. A rear lip spoiler was integrated to reduce the vehicle’s overall drag performance. Roof-mounted vortex generators (a particularly effective solution on three-box cars) were introduced. The car’s ride height was lowered a few millimeters.
Altogether, the drag coefficient was cut by some 20%, from 0.36 for the production
Other contributors to efficiency include an active control alternator that ensures the battery is charged only as required (to 12.8 instead of 13.5 V).
The sum of all the work that went into the Logan Renault eco² concept resulted in extra-urban NEDC driving cycle/UTAC-homologated fuel consumption of just 3.4 L/100 km, equivalent to CO2 emissions of 88 g/km.
Since driving style can play a significant role when it comes to curbing fuel consumption and CO2 emissions, the dashboard of the Renault Logan eco² concept features a gearshift indicator that enables drivers to contribute to the optimization of fuel consumption.