New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1919-03-02
What the Spark
Lever Is and
What 1t Does
Unless You Know Control
and Management of This
Part Of Automobile. You'll
Hardly Get Best Results
By II. Clifford Brokaw
Technical Director West Side Y. NJ.
[. \. Automobile School

t
Almost every driver understands that
this lever is moved to certain posi-
ton when starting the engine and to
another position after the engine is
running, but it is doubtful il many
persons understand why the lever is
spark lever indicate that many think
1t is moved to give hotter spark,
or more sparks. Others think that
retarding the spark shuts off the spark
entirely.
The spark lever is fer the purpose
OF controlling the time al which the
spark occurs with relation to the posi-
ton o. the revolving crank when igni-
ton takes place and power is gener-
atcd. 1t is desired TO have the gas
lgnited so it will expand and give
the piston a decided push at the mo-
mcnt III the revolution Of the crank
when the piston has stopped going up
IN the cylinder and is ready to start
down again.
To make this clear it might be we'll
30 explain the cycle of the ordinary
automobile engine. 1t is called four
cycle or four part cycle. because tho
operation is divided into four parts
or ssroEeS suction compress ion, power
and exhaust. On the first part. start
ing with tho piston at the top, the
crani, draws the piston down through
out the length of the cylinder and it
sucks III a charge OF explosive mix
ture gasoline and air.
Further revolution of the crank after
the Nisfon has reached the bottom Of
the cylinder drivce the piston up and
congresses the miyturc into q space at
the top of the cylinder varying in diff
teront motors from one-fourth to I
inch in denth. depending unon the
shnpe OF the combustion chamber. As
sumlng that the crank has been re
,olvine cloelwise. or right handed. the
spark should occur after the piston has
reached tho top Of the cylinder at the
end OF the compression strch, and has
started e. move dowu again frac. zion
az nj inch. This ihsures the continu-
ing nation of the cfanl,e IN right
lhnd direction by the powor Eefefated
- the burning gas miNture,
Warn the pistoh neArs the bottom
81 the eSihdef on this power stroke
tho exhaust NAlVu opens and remn ma
epen nhtll tho piston has reat he'd the
TOP of the cylinder once more on the
exhaust stfoke, Then the inlet Ynlyo
rgain opens and fresh charge is
cfhwn IN MS the piston travels down in
the cylinder.
II the spark should occur near the
end of the compression stroke. when
The piston stll was travelling up, the
crank would be in such position that
the force of the explosion would drive
the piston backward and revolVe the
crank counter cJockwisa, or left-handed.
This IS known as "kick- back" and
has been responsible for many broken
wrists. Therefore, when starting the
engine the spark lever is placed at
full retard. 50 that when the spark
occurs the piston will have travelled
Gown little way. carrying the oranl,
on in the right hand direction.
Power IS not generated the instant
the spark occurs. 1t takes a short time
only fraction OF a second-for the
gas to burn sufficiently to expand and
give pressure. When the engine is
cranked by hand it turns over so slow
y that there is very little movement
of the piston from the time the spark
occurs until the pressure is obtained
When. however, the engine is running
under its own power the speed is great
enough TO let the piston travel a short
distance between the time Of the spark
and the pinnacle of pressure; and when
piston will travel half the ler/,h of
tho cylinder before pressure is pro
duccd + the spark occurs with the
piston at the top of the cylinder This
would mean loss of power and waste OF
gasolene. as pressure would be main
tanned for such short part of the
stroke.
For this reason when the engine is
run at high speed the spark lever is
moved to an advanced position. This
causes the spark TO occur when the
piston still IS travelling UP on the com
preston stroke, but because of the
speed the piston has reached the tor
of the stroke and is ready to travel
downward before the pressure is gen
Grated When the engine speed is tt
be Increased the lever is to be movec
gradually to the advanced position
while the throttle is opened wide o,
the lever may be place at "advance'
immediatcly and the throttle opened
gradually.
In general the spark lever is placed
~ full retard when the engine is to bt
started and is advanced directly in pro
portion to the speed of the motor
speed Of the motor and not Of the cal
the exact point being determined b,
the power which the motor develop.
and the absence of knocking in tn,
engine That is, if the spark is too
far advanced the engine VIII knock ant
lose power. If it is too far retarded
the engine viii not give full power
either
Another point which enters int
the position at which the spark leve
should be carried and which il not ger
orally understood is that the spar
cannot be so far advanced when tn
throttle is wide open as with il close
or nearly closed. This Is due to tn
fact that with the throttle wide ope,
n greater amount of mixture is take
IN. When compressed it has highe
tempersturc-to point whore it is al
most self igniting. The result is yer
rapid combustion. Often it will b
found when climbing a hill that a knoc
in the engine may be overcome by clos
ing the throttle slightly instead of re
taTding the spark.
1t requires Il little experimenting t
determine just the position OF spar
lever and throttle at which the great
est power may be obtained under vary
ing road conditions. This 10 somcthin
evry driver should study gu. for hi
own car in the light OF the foregoins
1T should also be borne in mind whe
considering an old car that perhaps tn
Inkagc Of the levers is worn or Their
~ play Of the parts, which render
their operation uncertain. with thi
condition it is impossible to get an
dependable results
with magnetic ignition there is no
much movement Of the spark lcyeo re
CURED. u IL usually placed at rEtar
for starting the engine and is the
moved In advance, where it remains 70
a