The Washington herald., 1918-06-02
Efficiency AIDED BY
right THROTTLE Use
Correct Position Of Control Levers
When Driving Will Give In
creased Power.

One OF the least UNDERSTOOD le-
vers on the car is the spark con-
troll lever. Yet economy OF opera
tion, safety and a number of other
things depend upon its proper use.
The beginner retards 1t as directed
when starting, merely because he
has been told to do so. Such q
thing as control on the road, or
even the reasons for moving 1t at
all are completely beyond his knowl-
edge.
OF course, he knows that this le-
yer controls the spark which fires
the explosive mixture in the cylin-
ders. But the matter OF advancing
and retarding the spark 10 so haZy
in the minds of most motorists that
what follows will hardly be under
stood unless preceded by a few
words of explanation.
In order to have the engine run
in the right direction. the spark
must occur on the power stroke
just as the piston Is starting down.
II the spark should occur while the
piston is going up it might stop the
engine or start it running backward.
Evidently 1t is important when start
ing the engine to have the spark
occur on the downward stroke of
the piston. This is done by re-
tarding.
Ii the spark lever is advanced
too far, the explosion will occur on
the up-stroke of the piston, forcing
the fiy-wheel backward. and pos
sibIy injuring the operator IL he is
Cranking by hand, or breaking the
starting mechanism. With present
systems using self-starters there is
no danger of a broken wrist, but
something must give and it is usu-
ally the started gears or sprocket,
necessitating an expensive repair.
Easy to Retard Spark.
1t Is easy to retard the spark on
strange car if you understand the
procedure. Remove the cover of
the distributor so that you can
watch the distributor brush. Be
sure that switch is off. Crank
engine and note which way the
brush revOlves.
If it turns the same way as the
hands of a clock, we call it clock
wise" motion-if the opposite way.
it is -clockwise." Having
learned which way the brush turns
we must turn the distributor in the
same direction in order to retard
the spark. Remember the rule so
that you may always apply it cor
rectly. Turn the distributor in the
same direction as the movement of
the brush. This applies equally to
a magnetic. but here We watch the
turning of the drive shaft and turn
3 IL ~
is not even necessary to remove
the cover of the breaker-box. Crank
the engine. noting the direction of
rotation of the armature and move
the breaker-box in the same direc-
ton.
If 1t is necessary to retard the
spark in order to start the engine,
it is equally necessary to advance
the spark in order to give power
to the engine. The piston moves
SO rapidly that it will be part way
down the cylinder before the ex-
plosion catches up with 1t, so that
the most important part of the
stroke is lost.
By advancing the spark the ex-
plosion occurs earlier and the full
length Of the power stroke is used.
kkep Spark Advanced.
This matter Of advancing and re-
tarding the spark should be careful
ly attended to on the road. A safe
rule is always to keep the spark as
far advanced as possible short of caus-
ing the engine to knock. On some
cars the proper point is marked on
the sector; on the others the lever
Is pushed along to the limit of mo-
! ton. This is for use at all times, ex-
cept on a hill. As soon as the car
slows down appreciably what is
known as a spark knock" occurs,
This is due to the fact that the spark
occurs on the compression stroke. The
explosion meets the piston coming
down and endeavors to force it down,
causing a knock. This does not hap
pen on a level road unless the engine
is overloaded because the crank shaft
turns so rapidly that the piston has
time to pass head center and start
downward before the explosion pres
sure is developed. But when going
up a hill the engine slows down and
the knock occurs. The remedy, of
course, is to retard the spark Just
enough to stop the knock.
So 1t is necessary to keep the spark
OluCI " uCNCiOp lIc pOW-
er of the engine. But there is an
other important reason, and that is
to prevent the engine from overheat-
ing. We must ignite the gas in the
cylinder as early in the stroke as pos
sible in order to have 1t burn up be-
fore the exhaust valve opens. This is
to prevent the hame of the burning
gasses passing over the valves and so
oyerheatins and burning them. The
operator who runs with retarded spark
loses power. In order to overcome this
he opens the throttle wider than is
necessary, feeding more gas to the
cylinders than can be burned in the
short time before the exhaust valve
opens. The resulting fame, passing
through the valve ports, overheats the
engine.
The careful operator keeps the spark
lever Just ahead Of the throttle lever
on a level road. As he needs more
speed he opens the throttle more and
then advances the spark lever as well.