Combating automative engine valve recession

Abstract

[INTRODUCTION] Valve recession occurs when wear of the valve or seat inserts in an automotive engine has caused the valve to sink or recede into the seat insert (as shown in Figure 1). Excessive recession leads to valves not seating correctly and cylinder pressure loss. Leaking hot combustion gases can also cause valve guttering or torching, which will accelerate valve failure. Although new valve materials and production techniques are constantly being developed, these advances have been outpaced by demands for increased engine performance and wear related problems remain an issue. Dynamometer engine testing is often used to establish short-term solutions. This is time consuming and does not necessarily reveal the actual causes of wear. A long-term approach is required in order to understand fundamental wear mechanisms and the effect of varying engine operating conditions or design changes to the valve train. This information can then be used to develop tools for predicting wear and for solving problems more quickly if they do occur. In this case study, such tools were developed using a combination of component failure analysis, bench test work and wear modelling