With little more than 24 months of development work in direct gasoline injection (DGI), Renault SA launches its 2L 16-valve DGI 4-cyl. engine - the first of its kind from a European automaker.
The French automaker follows the gasoline direct-injection (GDI) pioneering of Mitsubishi Motors Corp., (Mitsu owns the rights to the "name" and acronym GDI) but with significant variations. The problem of the high sulfur content of European gasoline (compared with Japanese fuel) was tackled by greatly increasing the amount of recirculated exhaust gas (EGR) to 25%. This reduces the partial vacuum in the inlet manifold and, therefore, pumping losses. It retains a homogeneous and stoichiometric air/fuel ratio, which allows the existing catalytic converters to operate at normal efficiency - a problem for GDI engines when operating at lean air/fuel ratios.
Renault achieves parallel gains in fuel consumption, which is reduced further with a sequence of three varying air/fuel mixture ratios dependent on engine speed and load. The mixture moves from an initial stratified charge to a lean-burn and finally a richer mixture for power. Injectors supplied by Siemens AG operate at 1,450 psi (100 bar) pressure.
The shape of the Renault combustion chamber differs from Mitsubishi's in that its injector is placed centrally instead of to one side. This injector location - combined with specially contoured piston crowns - optimizes the stratified-charge combustion by concentrating the combustiblepart of the air/fuel mixture around the plug.
The DGI engine develops 140 hp and a substantial 148 lb.-ft. (201 Nm) of peak torque. It is now fitted to the new Renault Megane coupe and convertible, with other cars due to follow.
Another concept Renault is developing: a double-entry turbocharging system for gasoline engines. The turbine has a two-section, exhaust-driven wheel with separate inlet ports in a partitioned chamber, fed from paired cylinders one and four, and two and three, respectively. The split gas flow raises the maximum temperature at the turbine entrance for increased energy delivery from the compressor. This boosts thermal efficiency and transient response, with reductions in both turbo lag and fuel consumption. The first production application is planned for next year, says Renault.
A "camless" engine with electromagnetic valve actuators is a another Renault project, with research and development shared between several European companies.
The considerable electrical energy needed by such a system would be supplied by a combined starter/generator replacing the flywheel. BMW AG, PSA Peugeot Citroen SA, Volvo Cars and other European automakers also are investigating the technology. In addition to its electrical capabilities, the starter/alternator, in its high-speed motor mode, allows for further fuel savings by cutting engine power every time the vehicle briefly halts.