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A Variable Displacement Engine (VDE) improves fuel economy by deactivating half the cylinders at light load. The actual fuel economy benefit attained in the vehicle depends on how often cylinders can be deactivated, which is a function of test cycle, engine size, and vehicle weight. In practice, cylinder deactivation will also be constrained by NVH (noise, vibration, and harshness). This paper presents fuel economy projections for VDE in several different engine and vehicle applications. Sensitivity to NVH considerations is quantified by calculating fuel economy with and without cylinder deactivation in various operating modes: idle, low engine speed, 1st and 2nd gear, and warm-up after cold start. The effects of lug limits and calibration hysteresis are also presented.

In the Dual Equal variable camshaft timing strategy, the intake and exhaust events are equally phase-shifted relative to the crankshaft as a function of engine operating conditions. The primary emphasis is on improved fuel economy and emissions at part load. The external EGR system is potentially eliminated, with consequent improvement in the transient control of residual dilution. Additional benefits with optimized phasing are moderate improvements in idle stability and full load performance. In this paper, the Dual Equal VCT strategy is described, and engine dynamometer test results are shown which illustrate the benefits at part load, idle, and WOT. Implications of the strategy on phase-shifter response requirements and on the engine control system are discussed.

In this paper, four Variable Camshaft Timing (VCT) strategies are described: Intake Only, Exhaust Only, Dual Equal, and Dual Independent. The strategies utilize internal residual at part load for NOx reduction and fuel consumption improvement. The emphasis of the paper is a detailed comparison of part load data from steady-state engine dynamometer testing. Projections of EPA cycle fuel economy and emissions benefits relative to external EGR are also shown. Only limited data was acquired at idle and WOT. Implications of the strategies on the engine control system are briefly addressed.