ULEV and Fuel Economy - A Contradiction? 2000-01-1209
The CBR (Controlled Burn Rate) technology for MPFI engines is known to enable the reduction of throttle losses of gasoline engines by high EGR (Exhaust Gas Recirculation) rates due to the dilution tolerance of the swirl charge motion system using port deactivation.
Now a new aspect of CBR is being developed: extremely low emissions during and after cold start.
This paper is focused on the combustion stability and low emission aspects of CBR technology. It is shown how engine out emissions and catalyst light off behavior of an engine can be significantly improved using port deactivation. The very stable combustion directly after engine start, extremely retarded ignition timings in combination with lean engine operation and open valve injection with minimized wall wetting lead to very low HC emissions and very high exhaust gas temperatures.
ULEV emissions can be achieved with standard three way closed coupled catalyst technology up to luxury vehicles in the range of 2 tons inertia equipped with V8 engines.
Special emphasis is given to the possibility of combining ULEV emissions and improvements in fuel economy. Due to the variable charge motion provided by CBR and a special application of a „Miller-Cycle” ultra low emissions can be combined with an improvement in fuel economy of 6% compared to state of the art MPFI engines operated with EGR.