The Washington times., 1928-09-26

tenSlV6 research Work going
assurance is given by engine
made an exhaustive study of
A study of compression noise
shows that it is at its maximum
during acceloration over certain
speed ranges which may vary for
different makes of cars or even
for the same make of car under
varying conditions. Practically all
high compression engines become
quiet when the car attains its roll
ing speed.
The thing that is stimulating in
terest in the process of eliminating
power noise is the fact that the
problem Is believed to have been
virtually overcome by one OF the
large manufacturers. Competitors
are studying this car as they have
never studied cars before, search
ing for the clew to the solution.
Better driving is regarded as mere
w a temporary remedy. but 1t is
being advocated nevertheless, since
il has not been established
Nhekuer thu mechanral remedy is
something that Will be available 10
present Users.
MUFFLER UNDER SUSPICION
suspicion points to the muffler.
many engineers believing that the
exhaust gases of higher speed.
higher compression engines have
placed too great a burden on the
exhaust system.
This accounts, in part, for the
number of muffler changes within
the last two years, some concerns
having gone from mufflerS that
have served them well for years 70
types embodying radically different
principles OF silencing.
Many experts are surveying the
possibilities in insulating the null
fIer from the frame and some own
ers already have made such 2
change.
The practice is to hang the NUT.
fIer from the frame by means OF
metal brackets, but this arrange
ment is thought to encourage the
teIegraphing of exhaust noises to
the chassis end, Of course, TO the
Enclosed body.
Heat at the muffler complicates
the problem, but some experiments
are being made with composition
materials which may overcome TINS
objection.
High compression is desirable
from the efficiency as well as int
performances standpoint. 1t contrlo-
utes to safety by making the en-
CINE an effective brake when go
ing downhill.
With these outstanding points In
its favor, engineers are willing TO-
go to almost any limits to silence
the compression noises rather than
TO turn aboutface at this stage
OF automotive progress.
Greater Volume. Need
The burden on the present-day
muffler Is due to the need for han
ding a greater volume Of mor2
highly compressed charges that ara
exhausting at more rapid rate.
A muffler merely provides a
means whereby gases can expand
by degrees rather than to exhaus-
and expand rapidly into the All
directly after leaving the comblis-
ti0n chambers.
At the present moment the stu
alton is shown to be one Of over
loading. The muffler has more
work than 1t can do. As result,
the expanding gases set up vibra-
through a large portion OF their
expansion after they leave the mui'
fIer itself.
IL the final exhaust pipe Is not
large enough or IL 1t has a peculiar
shape it, too, may add to the
power noise and cause passengers
fn 0nrdYNlafv ne drnnfVnu n.16
ming.
During acceleration, especially be-
tween 80 and 40 miles an hour, tUis
noise may become a defeaning roar.
Strangely enough, at higher speeds
many high compression, engines
seem to run quietly.
Two leading manufacturers have
provided a partial cut-out which
helps to take care Of this problem,
and it is plan which may be tried
by any owner who finds his engine
and exhaust system bothersome.
BY providing a bypass around the
muffler for about half the exhaust
ing gases the muffler is spared the
ordeal of being overloaded. The, re-
suits are very noticeable to the pas
sengers.
Really No Bother
TO bypass a portion Of the ex-
hausting gases, however, means in
creasing the noise at the tail pipe.
This does not bother the occupants
OF the car. but it attracts the notice
or other users of the highway.
Many owners have noticed that
power noises moderate after a car
Is broken in, especially after IL
has been driven 5000 to 10000
miles. This is explained by the
tact that an accumulation of carbon
In the muffler takes the sharp
edges ofc the plates and rounds out
the corners.
The gases thus pass through the
passages more smoothly and with
less vibration of the muffler plates.
ANY automobilist who is ANNOYED
by the exhaust noises of his car
or by compression noises which
are telegraphed to the car BODY
should keep his ears and ewes
open for new Developments, in ex,
haust systems and particularly in
improvements in mufflers,
A. new muff1er Is inexpensive and
the indications are that suner.
silent types will be available within
the near future.
High compression must be re.
tanned. but the manufacturers are
determined to retain 1t without
sacrifice Of quiet and comfort.
Copyright, 1928