In a divided-exhaust turbocharging system, 1 exhaust valve and port from each cylinder can be directed to the turbocharger turbine (referred to as the Blowdown Path) and the other can bypass the turbocharger (referred to as the Scavenge Path). The Blowdown and Scavenge valve events are determined based on the functions of the blowdown and displacement phases of the exhaust process.
In our previous publications of another version of Divided Exhaust Period Turbocharging, the Valve Event Modulated Boost system (VEMB), we demonstrated significant engine efficiency and performance improvements over the base turbocharged engine. Reductions in pumping work and high-load Residual Gas Fraction are the primary reasons for efficiency and performance improvements.
In this project we have evaluated through simulation and engine testing, the further advantages of the Divided-Exhaust-Boost (DEB) system version of Divided Exhaust Boosting; a version that does not require a concentric-camshaft for boost control. This system retains the previously-reported very large improvement in catalyst light-off performance, which is to be expected from a system that can completely remove the turbocharger from the exhaust pathway during the cold-start period.