Advances in Static and Dynamic Exhaust System Sealing 1999-01-0597

As the automotive industry continues to keep pace with new emissions regulations, the requirements of exhaust system joints become increasingly demanding. These joints, both static and dynamic, must not only prevent the release of untreated exhaust gas, but must also combat the ingestion of oxygen into the exhaust system, which could have adverse effects on the closed loop emission control system. In order to meet these stringent demands, a “system” approach to joint design must be coupled with advances in seal and gasket material, geometry and construction.

Three particular types of joints will be discussed - static flange-to-flange joints, static spherical joints and dynamic spherical joints. Dynamic joints are typically used in transverse mounted engine, front wheel drive vehicles to “decouple” the engine rolling motion from that of the exhaust system. Static flange-to-flange joints are used in various locations throughout the exhaust system. Although these joints provide good positional control, they do not compensate for assembly misalignments. Static spherical joints are typically used to connect the exhaust manifold to the remainder of the exhaust system. The ball and socket nature allows the joint to be bolted solid at a variety of different angles, compensating for build variations.

The sealing ability of current exhaust joining techniques is compared to those of the advancements presented. The test data indicate the improvement possibilities when these advances are implemented.