The influence of cylinder deactivation on the emissions and fuel economy of a four-cylinder direct-injection diesel engine

The potential benefits and limitations of deactivating two of four cylinders by cam switching to disable the intake and exhaust valve lift were investigated experimentally on a turbocharged four-cylinder common-rail direct-injection diesel engine. When running on two firing cylinders, at light engine loads (a brake mean effective pressure of 2 bar, based on four-cylinder operation), the brake specific fuel consumption at given engine-out nitrogen oxide levels is comparable with or marginally better than when the engine is running on four cylinders. Cylinder deactivation allowed higher fuel rail pressures to be used to reduce the soot emissions while maintaining the advantages of lower carbon monoxide emissions and lower hydrocarbon emissions. At engine loads with a brake mean effective pressure of up to 3 bar on four cylinders, cylinder deactivation lowered the carbon monoxide and hydrocarbon emissions and raised the exhaust gas temperature by around 120 °C but, at higher loads, the fuel economy deteriorated and the soot and nitrogen oxide emissions increased markedly. The benefits of cylinder deactivation are therefore limited to light-load operating conditions, where the fuel economy is improved, the hydrocarbon and carbon monoxide emissions are reduced and the exhaust gas temperature is raised.