Dual Equal VCT - A Variable Camshaft Timing Strategy for Improved Fuel Economy and Emissions

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.