Chapter 13 Exhaust Systems 291 Copyright Goodheart-Willcox Co., Inc. Vertical Muffler The vertical muffler system takes the exhaust gases from the exhaust manifold turbocharger outlet, pipes them to the rear of the cab, then upward through a single muffler and stack into the atmosphere, Figure 13-22A. This system is most common on road tractors, but is also used on straight trucks. It directs fumes up and out and allows easy access to the muffler and stack. Vertical stacks might be pleasing to the eye, but they cost more than underframe systems and are more vulner- able to damage from jackknifing and overhead obstacles, such as tree branches. They can present clearance prob- lems with close-coupled trailers or truck bodies that are snug to the cab. When attached to the cab instead of to a separate vertical support, vertical stacks can transmit noise and vibration to the driver’s compartment. As newer diesel engines breathe cleaner to meet federal emissions regula- tions, the need to get the exhaust outlet high up into the air is becoming less important. Horizontal Muffler Horizontal mufflers with short tailpipes (tailspout) that are aimed downward are shorter, simpler, and lighter than vertical mufflers and stacks, Figure 13-22B. Though it is not common practice, many heavy duty trucks may be equipped with horizontal systems in the near future. Drawbacks to horizontal systems include higher restriction from mufflers that must be short and compact, and increased noise from sound waves reflected off the pave- ment. Also, thermal shock from road splash tends to shorten the life of mufflers mounted close to the road. Because the outlet pipe generally bends toward the ground, the strong exhaust flow can kick up dust from dirt or dry gravel surfaces. This can be especially bothersome for vehicles regularly running on such surfaces. A variation of the horizontal muffler is hung on the frame but the outlet pipe winds upward along the cab’s corner or side, Figure 13-22C. The muffler’s outlet can be Fluid in Fluid out Exhaust gas in Exhaust gas out Figure 13-21. Exhaust gas flow through a heat recovery silencer. (Nelson Industries) A B C Rain cap Stand pipe Muffler Muffler Rain cap Stack pipe Exhaust pipe Exhaust pipe Wye connector Wye connector Resonator Resonator Muffler Exhaust elbow Manifold connectors Manifold pipe Manifold pipe Manifold connectors Tail spout Resonators Exhaust elbows Exhaust pipe (straight or flexible tubing) Exhaust pipe (straight or flexible tubing) Exhaust pipe (straight or flexible tubing) Figure 13-22. Three popular exhaust system layouts used in mobile diesel engine installations. A—Vertical. B—Horizontal. C—Combination. (Nelson Industries)