Laboratory test rig simulation of bore polish

Abstract

Bore polishing is a tribological process in which the cylinder bores of an internal combustion engine are very mildly abraded to generate featureless planar surfaces with part or total loss of the honing pattern. In practice, bore polish can be controlled by lubricant formulations and a number of industry standard engine tests have been developed accordingly but at very high cost. The typical cost of the present bore polish engine test, based on the Mercedes OM364A, is in excess of £30000 a test. Considerable economic benefits could therefore be achieved if a simulative rig test to evaluate bore polish existed to study the influence of material and lubricant chemistries prior to engine test evaluation. In this paper a pin-on-plate reciprocating tribo-test rig has been developed and used to successfully discriminate between the reference lubricants (RL133 and RL134) used in the Mercedes OM364A bore polish engine test. Optical microscopy and surface profilometry were used to analyse the worn surfaces and confirm bore polish. The results show that bore polish was repeatedly generated under simulated engine temperature conditions using carbon black as oil contaminant. Further work is now required to refine the test method.