Preventing Catastrophic Camshaft Lobe Failures in Low Emission Diesel Engines

J. A. Mc Geehan; P. R. Ryason

doi:10.4271/2000-01-2949

2000-10-16

Preventing Catastrophic Camshaft Lobe Failures in Low Emission Diesel Engines 2000-01-2949

With the drive to reduce emissions and improve fuel economy, fuel injection pressures have increased. This has increased Hertzian stresses on the roller follower cam system to the point that cam lobe contact fatigue failure has become the “Achilles heel” of diesel engine durability in the 1990s. Contact fatigue failures have occurred on both injector lobes and the exhaust and inlet lobes. This is particularly the case in fleets with frequent engine shut downs and starts, stop-go service and in some line-haul fleets.

This paper describes field service cam failures across several engine types and applications. In our experience supporting fleet customers in cam failure analysis, we found that a combination of ten critical independent variables must be correct in order to prevent cam lobe contact fatigue failures. These variables are each discussed separately.

In bench tests simulating stop-go applications, we found that the silicon nitride roller on a steel pin had low and constant friction under flooded and starved lubrication conditions. In contrast, the bronze pin and steel roller had severe stick-slip with very high friction, which could cause roller skidding on the cam. The silicon nitride roller and steel pin have provided long cam life in many applications.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Digital $37.00 Print $37.00

Preview Document

We also recommend:

Standards

SAE Mobilus®

Publications

News

Events

Professional Development

A World in Motion (PreK-12)

Participate with SAE

SAE Membership

Donate

Preventing Catastrophic Camshaft Lobe Failures in Low Emission Diesel Engines 2000-01-2949

SAE MOBILUS