THE MUFFLER
Much despised, detested by many automobile operators and neglected
by almost every chauffeur, and even “cut out” altogether when the
traffic policeman is not around, the muffler plainly ought not to be
so treated. It is deserving of careful consideration every once in a
while, if the owner cares much for efficiency and economy in operation.
The muffler is located under the car, and being out of sight is usually
out of mind. It is therefore often neglected or misused. And yet it
ought not to be. The muffler is placed on the end of the exhaust pipe,
and its sole purpose is to silence the exhaust of the engine so that
the driver of an automobile while taking pleasure himself does not
wholly deprive others of it.
Let us consider the use of the muffler. The exhaust valve opens while
the burned gas is still under a pressure of from twenty-five to thirty
pounds per square inch. If this were exhausted directly into the
air the resulting noise would stifle conversation in the car, annoy
everybody along the street, and quickly get the driver into trouble
with the police. The muffler prevents all this. It provides a chamber
in which these exhaust gases may expand and cool somewhat and at the
same time breaks up the pressure by allowing it to leak out slowly
through a number of very small holes, instead of letting it loose in
one “big noise.”
In the early history of the automobile, mufflers were not used and
everybody for blocks around knew when an auto was coming. As the
automobiles increased in number this became a nuisance and was stopped
by law. Then they sought—indeed had been seeking—a means of stifling
the sound. In the early muffler there was trouble because the gas would
back up in the cylinder and decrease the power of the motor. It was
thought there was no way to decrease the sound without decreasing the
power; therefore the manufacturers devised a valve to “cut out” the
muffler on the car whenever extra power was desired.
Sometimes the back pressure was so great as to interfere when driving
through heavy roads or up hills. The “cut-out” let the gas exhaust
directly into the air instead of going through the muffler. At the
present time nearly every city has a law prohibiting the use of
“cut-outs.”
As a matter of fact those well posted on automobile engines understand
to-day that the “cut-out” is absolutely unnecessary on a modern car if
the muffler is kept in proper condition. Muffler manufacturers have
been able to produce a design with which there is no back pressure at
all. For this reason manufacturers discourage the use of the “cut-out”
on their cars and some of them will no longer install one except as an
“extra.”
The average driver, however, does not know that his muffler needs as
careful attention as any other part of the mechanism and so he neglects
it. In these days of noiseless cars it requires a great number of very
small holes inside the muffler. These become clogged with soot or
carbon from the exhaust. The deposit collects very rapidly, especially
when the grade of oil used is poor or too much oil is used. It also
results when the carburetor is adjusted to give too rich a mixture.
When these small openings become clogged, the exhaust gases cannot
escape readily and naturally the cylinder of the engine is not cleaned
at the exhaust stroke. Result: It is impossible to bring in a full
cylinder of new gas on the next intake stroke. There is not a full
charge to explode and this means a loss of power to the engine.
Cases are known where the throttle was opened wide without any increase
in power. Trying to find out what the matter was the driver opened the
“cut-out” and this caused the machine to accelerate very rapidly.
In other cases when the engine was cranked, there would be a few
explosions, a sputter and a stop, and the reason was that the muffler
was so clogged that it was impossible to exhaust the gas from these few
explosions, the cylinder remained full of burned gas, and, of course,
could not take in a further supply. These, of course, are extreme
cases, but the writer had this experience not long ago:
He was riding in a car that could hardly make headway against a strong
wind blowing. This meant frequent use of the second-speed gear, which
in itself causes an undue use of gasoline. He found on experimenting
that the muffler “cut-out” pedal could be used in place of the
accelerator pedal; that is, when the muffler “cut-out” was open the
engine had considerable more power and immediately speeded up. In fact,
he kept the “cut-out” open most of the way home and had no more trouble
in bucking the headwind. The experience led to the discovery that the
muffler was almost totally clogged with carbon.
Of course, where the engine is stopped or there is a decided decrease
in power, the owner will hunt for the trouble, and find it, perhaps, in
the muffler. He might not notice less serious cases where, while the
muffler is somewhat clogged, it does not decrease the power strikingly;
but even in these less serious cases it will often be found that the
power of the motor may be materially increased by having the muffler
cleaned. Yet it is seldom done, even when the car is supposed to be
overhauled completely. Many drivers seem to think the muffler can take
care of itself. In looking over the inspection card of a well-known
make of car it was found that no provision was made for even looking at
the muffler. The service-station inspection orders contain no mention
of the muffler.
There is still another cause of the clogging of the muffler with
carbon, and that is the practice of putting kerosene in the cylinders
to clean them. The kerosene cleans the carbon from the cylinder walls
and that is what makes the trouble, for it is exhausted right into the
muffler. Some drivers understand this and when using kerosene for this
purpose open the muffler “cut-out”; this allows the discharge of the
greater part of the carbon into the air, but even then some of it finds
its way into the muffler and in time makes trouble.
A muffler of modern design, if kept clean, needs no “cut-out”
arrangement, but if it becomes clogged it is necessary to use a
“cut-out” when the full power of the engine is needed. The consequence
may be a trip to the police station and then to the court and then a
fine to be paid. It is evident, therefore, that if one wishes to get
power out of his car on an economical basis and wishes to escape fines,
he should look after his muffler.
Since instruction books, and even service-station inspection charts do
not say much about the muffler, and since it is evident that it has an
important part in the operation of the car, where the owner does not
find sufficient information concerning it from the instruction books
furnished him, he would better ask the agency to furnish him a special
muffler pamphlet, which will show its construction and care.