CHAPTER XXIII
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.