(fig. 4-49) reduces the
acoustic pressure of exhaust gases and discharges them to the atmosphere with a minimum of
noise. The muffler usually is located at a point about halfway in the vehicle with the
exhaust pipe between it and the exhaust manifold and the tailpipe leading from the muffler
to the rear of the vehicle.
The inlet and
outlet of the muffler usually is slightly larger than their connecting pipes, so that it
may hook up by slipping over them. The muffler is then secured to the exhaust pipe and
tailpipe by clamps.
muffler has several concentric chambers with openings between them. The gas enters the
inner chamber and expands, as it works its way through a series of holes in the other
chambers and finally to the atmosphere. They must be designed also to quiet exhaust noise
while creating minimum back pressure. High back pressure could cause loss of engine power
and economy and also cause overheating.
components usually are made of steel. They are coated with aluminum or zinc to retard
corrosion. Stainless steel also is used in exhaust systems in limited quantities due to
its high cost. A stainless steel exhaust system will last indefinitely.