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Unconventional Variable Valve Timing

Oil pressure actuation of variable valve timing units is pretty commonplace—despite the intricacy of the actuation units—and most are found on overhead cam engines.

Oil pressure actuation of variable valve timing units is pretty commonplace—despite the intricacy of the actuation units—and most are found on overhead cam engines. Now BorgWarner Morse TEC (www.bwauto.com) has begun volume production of what it calls "the next generation of cam phasing:" a "torsional assist" unit that utilizes camshaft torque to provide the actuation energy. The combination of a center-mounted spool valve and check valve allow the camshaft’s torsional energy to assist actuation, rather than oppose it. This design eliminates the need for an upsized oil pump and its associated parasitic losses, which BorgWarner claims gives its unit a fuel economy and emissions advantage when compared to oil pressure-activated systems. Other benefits claimed include quicker actuation, a larger operating range, and greater phase stability. It can be applied to both overhead cam and overhead valve engines, and will debut on the 3.5- and 3.9-liter overhead valve V6s used in the 2006 Chevrolet Impala and Monte Carlo, and Pontiac’s G6.