Technical Paper
Divided Exhaust Period - A Gas Exchange System for Turbocharged SI Engines
2005-04-11
2005-01-1150
The necessity to limit the boost pressure in turbocharged gasoline engines results in higher exhaust pressure than inlet pressure at engine speeds when the wastegate is opened. This imbalance has a negative influence on the exhaust scavenging of the engine and results in high levels of residual gas and consequently the engine is more prone to knock. This paper presents a study of a gas-exchange system for turbocharged SI engines. The concept aims at improving the performance and emissions of a turbocharged SI engine by dividing the exhaust flow from the two exhaust valves into two different exhaust manifolds, one connected to the turbocharger and one connected to a close coupled catalyst. By separating the valve opening period of the two valves and keeping the duration of both valve opening events shorter than 180 crank angle degrees, the disturbance of the exhaust blowdown pressure pulse during valve overlap in a four cylinder engine can be completely eliminated.