It has been clearly demonstrated separately, that the application of both Dual Cam Phasers (DCP) and External Cooled EGR systems are highly beneficial to improving the efficiency of highly-boosted GDI engines. DCP systems can optimize the volumetric efficiency at WOT conditions, improve boost and transient response at low engine speeds, and provide internal EGR at low RPM part-load conditions. External cooled EGR has been demonstrated to dramatically improve the fuel consumption, lower turbine inlet temperature, and improve emissions at high power conditions.
In previous investigations by the BorgWarner Engine Systems Group, we showed that full engine speed/load range EGR coverage can be obtained by combining High Pressure Loop and Low Pressure Loop external EGR systems with a DCP strategy.
In this report we will present further studies of the factors that provide a strategy for mixing LPL and HPL in the region of the engine map where the engine has sufficient delta-P across the systems to flow both loops without additional throttle of backpressure devices.
Additionally, we present the benefits of pre-close-coupled catalyst source for the LPL EGR system.