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An experimental analysis was executed on a NA (Natural Aspirated) 4-stroke gasoline engine to investigate the potential of exhaust waste energy recovery using power turbine technology for light duty application. Restrictions with decreasing diameter were mounted in the exhaust to simulate different vane positions of a VGT (Variable Geometry Turbine) and in-cylinder pressure measurements were performed to evaluate the effect of increased exhaust back pressure on intake- and exhaust pumping losses and on engine performance. Test points in the engine map were chosen on the basis of high residence time for the vehicle during the NEDC (New European Driving Cycle). The theoretically retrievable power was calculated in case a turbine is mounted instead of a restriction and the net balance was obtained between pumping power losses and recovered energy.

Due to rotating inertias within the engine and transmission, the response of a vehicle during large engine speed shifts may appear reluctant or even counteractive. To overcome this behaviour, a CVT drivetrain was augmented with a powersplitting planetary gear stage and steel flywheel in the so-called Zero Inertia (ZI) powertrain [1]. This transmission concept managed to combine two contradictive goals: the driveability in terms of the pedal-to-wheel response is greatly improved; and a large leap towards optimal fuel economy can be made. These goals were achieved by cruising the vehicle at extremely low engine speeds, enabled by the large ratiocoverage of the CVT. The flywheel acts as a 'peakshaver' during engine speed transients: it delivers power during (semi-) pedal kickdown and absorbs the engine's kinetic energy at pedal back-out.