On their own market, European car manufacturers must face high constraints, especially in three domains: environmental issues, reliability and development time reduction. For environmental issues, they have to combine fuel economy and low exhaust emissions. Diesel engines are a very cost effective way to reduce fuel consumption. However, to satisfy new standards on exhaust emissions, Diesel particulate filters and NOx traps will be necessary. These devices, associated with downsizing, will severely increase thermal and mechanical loads on engine main parts. Reliability has a great impact on brand image. The competition on this point leads to longer warranty periods and mileage targets, associated with lower failure rates. Development time reduction allows accelerating models renewal, which is also an important factor of competitiveness.
In order to satisfy these three contradictory constraints on Diesel engines development, RENAULT Powertrain engineering division has developed an overall methodology that allows to validate and optimize field reliability during development and before start of production. This paper presents this overall methodology, which combines numerical simulation and experimental characterization. It is then illustrated by examples focused on a recent Diesel engine 16 valves cylinder head.