Impact and observations of cylinder deactivation and reactivation in a downsized gasoline turbocharged direct injection engine

Cylinder deactivation, sometimes referred to as Variable Displacement Engine (VDE) technology, is a method being employed in state-of-the-art reciprocating engines to improve fuel economy. The approach involves disabling the valve actuation of one or more cylinders to deactivate them, thus forcing the engine to operate at a higher specific load across the remaining cylinders to produce the torque demanded. Operating at such a point with an increased throttle opening reduces the engine’s pumping losses and hence reduces fuel consumption. In this work, the spray morphology, combustion and emissions of a three-cylinder downsized gasoline turbocharged direct injection (GTDI) engine with VDE capability on one cylinder were studied. This investigation allowed the interaction between the fuel spray, engine performance and emissions immediately following the reactivation of the deactivated cylinder to be better understood. Three operation modes were examined which included running the engine at full displacement, at the reduced displacement and at full displacement with increased indicated mean effective pressure (IMEP), matching that of the reduced displacement mode. The study showed that cylinder deactivation significantly reduced specific fuel consumption at the conditions tested in comparison to full displacement operation. It was also found that when running the engine at full displacement but with the reduced displacement level IMEP, the specific fuel consumption was greater than for reduced displacement operation. In addition, it was observed that particulate number (PN) emissions increase transiently during the deactivation period due the disturbances to the fuelling control caused by displacement transitions. Improved fuelling control, refinement of the engine calibration during reduced displacement operation or a Gasoline Particulate Filter (GPF) could be used to manage this PN level.