1994-10-01

1.8L Sierra-Mondeo Turbo-Diesel Valvetrain Friction Reduction Using a Solid Film Lubricant 941986

A 1.8L turbocharged diesel engine valvetrain friction was investigated, and the effectiveness of using a solid film lubricant (SFL) coating in reducing friction was determined throughout the operable speed range. This valvetrain design features direct acting mechanical bucket valve lifters. Camshaft journal bearing surfaces and all camshaft rubbing surfaces except lobe tips were coated. The direct acting bucket shims were etched with a cross hatch pattern to a depth sufficient to sustain a SFL film coating on the shim rubbing surfaces subjected to high surface loads. The SFL coated valvetrain torque was evaluated and compared with uncoated baseline torque. Coating the cam bearing journal surfaces alone with II-25D SFL reduced valvetrain friction losses 8 to 17% for 250 to 2000 rpm cam speed range (i.e. 500 - 4000 rpm engine speed). When bucket tappet and shims were also coated with the SFL, further significant reductions in coated valvetrain friction were observed. These reductions in friction ranged from 14.4% to 35% for camshaft speeds of 250 to 2000 rpm. Limited durability tests showed that the II-25D SFL impregnated to a depth of 20 microns will provide 3000 hours or more of service life.

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