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Twin camshaft phasing was applied to a 1.6l 4-cylinder 16-valve DOHC engine. Both camshafts - intake and exhaust - were equipped with continuously adjustable cam phasing units. Different operating strategies were compared with regard to mechanical feasibility, thermodynamics and calibration. Attractive part load fuel economy was achieved with two different phasing strategies. With regard to full load and idle a preferred twin camshaft phasing strategy was determined. It was found favorable to shift the intake camshaft largely towards ‘advance’, and the exhaust camshaft towards ‘retard’. Maximum fuel economy improvement was 8% at 2500 rpm and 3 bar mean effective pressure. In the European drive cycle 5 % fuel economy improvement was obtained. To achieve superior performance it is mandatory to combine twin camshaft phasing with an appropriate exhaust system and optimized cam events.