Lesson 3
The dual exhaust permits the exhaust gases to travel in a straighter path to the rear of the vehicle.
Therefore, the dual exhaust system causes less back pressure than the single and is desired for best engine
performance. However, the additional parts make dual exhaust systems more expensive than single exhaust
systems.
If a single exhaust system is used on a V-type engine, the exhaust gases from the two banks of cylinders
must be brought together at some point. On some engines, a crossover pipe made from a steel tube
connects the two exhaust manifolds. Exhaust gases from both cylinder banks then leave through one
exhaust pipe that is connected to one of the exhaust manifolds. Another method is to bring together the
exhaust pipes from the right and left cylinder banks, forming a "Y" connection.
TURBOCHARGER
A turbocharger, when used, is mounted in the exhaust system. Its turbine housing is generally connected
directly to the outlet of the exhaust manifold. All exhaust gases leaving the manifold pass through the
turbine housing, to drive the turbocharger, and then escape through an exhaust elbow to the exhaust pipe.
Driving the turbocharger slows down the exhaust gases somewhat. As you know, slowing down the exhaust
gases reduces the engine's power output. With the turbocharger, however, the power loss due to slowing the
exhaust gases is more than made up by the increased intake air pressure.
SPECIAL BYPASSES
Water tankers of 2 1/2-ton trucks have a special bypass in their exhaust systems. The bypass is used in cold
weather to direct the hot gases into a chamber under the water tanks to help keep the water from freezing.
A bypass control valve is mounted in the exhaust system at the rear of the exhaust pipe and in front of the
muffler. The control valve can direct the exhaust gases either to the muffler or to the chamber under the
water tank. A control lever to operate the bypass control valve is located in the vehicle cab.
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