Effect of lubricant chemistry on the performance of end pivoted roller follower valve train

• Lubricant viscosity plays a key role on end pivoted roller follower slip.
• Anti-wear agent and friction modifier do not contribute to roller slip.
• Viscosity index improver had an effect on roller slip.
• Synthetic base oil helps in reducing slip as compared to mineral oils.
• Phenomenon of negative slip was also observed at certain conditions.

Real production engine employing end pivoted roller follower valve train has been instrumented to investigate the effects of engine operating conditions, lubricant rheology and chemistry on the sliding of rollers. The experimental results showed that due to shear drag it was not necessary for roller rotational speed to increase with camshaft speed. The lubricant viscosity played a key role in the roller slip at lower temperatures however at higher oil temperatures negative slip was also observed indicating that component inertia and internal friction have a role to play in roller slip. The results also clearly showed the impact of viscosity improvers on roller slip. The experimental setup, test procedure and results are presented in this research work.