Abstract
The benefits and limitations of cylinder deactivation for light duty diesel engines have been investigated. Two of four cylinders were deactivated by switching to zero-lift cams for the intake and exhaust valves on a turbocharged, 4 cylinder common rail direct injection diesel engine. When running at light engine loads (2bar BMEP, based on 4 cylinder operation), cylinder deactivation had no effect or improved BSFC at given engine-out NOx levels. Cylinder deactivation allowed higher fuel rail pressures to be used to reduce soot emissions whilst maintaining an advantage in lower HC and CO emissions. At engine loads up to 3bar BMEP on 4 cylinders, cylinder deactivation lowered CO and HC emissions and raised exhaust gas temperature by around 120°C. At higher loads, fuel economy deteriorated and soot and NOx emissions increased markedly. The reduction in engine charge flow rate resulting from deactivating two cylinders limited the boost available. The resulting lower AFR and restricted level of EGR available were the main reasons for the deterioration in emissions at higher load conditions. At similar indicated loads, higher boost values available when running on 4 cylinders produced lower soot and CO for a relatively small reduction in the benefit of higher exhaust gas temperature, indicating boost revisions would extend the useful range of cylinder deactivation.
Published Version
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