Heavy Duty Off-Road Truck Exhaust System Design 2009-01-2853

An important segment of power system design often left to the Original Equipment Manufacturer (OEM) is the engine exhaust system. The requirement of exhaust after treatment has increased the importance of exhaust systems to be impermeable and still retain their physical flexibility. To achieve the necessary flexibility, OEMs will often choose to incorporate an available expansion joint(s) into the exhaust system. Often, conversations with expansion joint suppliers result in the OEM having to supply vital information about the application or a vehicle to record acceleration and vibration information. Unfortunately, the cost of building low volume vehicles does not always afford the OEM with enough resources to develop a custom expansion joint for the exhaust system. As a result, it is important to understand what the proper inputs are, make a sound engineering judgment as to what the worst case magnitude may be and provide that information to different suppliers. Comparing feedback from the suppliers will assist with the selection of a part which fits the application and meets all of the design requirements.

Vehicle maintainability and ease of assembly are areas sometimes overlooked when designing the exhaust system. The potential size of exhaust system components can result in them being difficult to handle, making it important to analyze maintainability and assembly concepts prior to design. Proper design can alleviate build tolerance issues, simplify maintenance and teardown procedures and improve assembly.

For assembly, the designer must first focus on how the rest of the vehicle was designed and the intended assembly procedure. For exhaust system design it is common that the surrounding components have already been conceptualized, simplifying the determination of assembly sequence and space constraints. Once the intended assembly sequence is understood, designing a system that fits into the assembly process is much easier. For maintenance, the designer must take into consideration how often the exhaust components will need to be maintained, and more importantly, during what other maintenance procedures must all or part of the system be removed.

As engine and emission technologies advance a robust, maintainable, assembly friendly exhaust system becomes more important. This results in the priority and significance of the exhaust system design increasing within the vehicle design process.