Delphi wants super-turbo systems for lean gasoline

摘要

Compression ignition gasoline engines running lean, dilute mixtures need better boosting systems. Increased air mass flow and exhaust gas recirculation (EGR) rates needed for low-temperature combustion can mean that single- and even dual-stage turbos are no longer able to function efficiently over the engine's operating map. Delphi said: "Turbo system performance is degraded by low-temperature exhaust, EGR and late intake valve closing. A two-stage supercharger plus turbocharger system that also has two charge air coolers can supply the air needed." As featured in the June 2012 issue of Automotive Engineer, the Tier One is developing a gasoline compression ignition process. Thermal efficiency is higher than spark ignition because combustion is cooler. Lean mixtures with EGR rates of up to 50% promise low particulate and NOx emissions.