Benchmark diagnostic capabilities Swirl valves
Customer: Tier 1 supplier to the automotive industry
Market: Light duty on highway – United States
BRACE execution: OBD Competence Cluster
Location: BRACE offices
Swirl valves are used in the inlet chamber of certain Diesel engines. By keeping the swirl valves closed at lower speeds/loads of the engine the way the intake air enters the combustion chamber is closer to the optimum for a good air and fuel mixture. At higher speeds/loads the swirl valves open to also have an optimum air intake flow to the combustion chamber.
Damages to the swirl valve system or failures in the opening or closing therefore impact the combustion and may result in increases in exhaust gas emissions.
Swirl valve systems are explicitly mentioned by the Californian legislator for monitoring. Typically these system consists of an electronic or a vacuum actuator, some linkage mechanism and a shaft with butterfly valves. Adding feedback position sensors for diagnostics is therefore complex as the feedback must be able to notice when anywhere in the system something goes wrong. A typical position feedback inside the electronic actuator for example might not be acceptable for California OBD.
To support the Tier I on understanding the requirements BRACE analysed the CARB legislation and looked for examples of swirl valve systems already used on the US market. BRACE used the US Service Information Websites of a number of OEMs as they are required to provide information on how their OBD systems function. A study was done on which vehicles use swirl valves, what type of feedback position sensing was done and what failure modes could occur and by what diagnostics would these be detected.