Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1919-05-18
.e|MPL|F|ED LESSONS IN
{ CARE OF AUTOMOBILE
Guerrlick Continues His Description
OF Carburctor and Its
Functions.
HOW ENGINES SPEED VARIED
Iimcs-Dispatch's Expert Automobile
Trouble Solver Answers Many
= Questions i'm Plain Language for
: Readers With Machine Problems.
(carburctor. Continucd)

The carburetor, as far as IL was ex-
planned in the last lecture. would he
-all right for n single speed, uniform
load engine. but the engine Of the
automobile must have many speeds.
and be able TO overcome varying loads.
ENcrc must. therefore. be a number OF
stditions 10 the carburetor as ex-
Flaincd so far.
First, LEI us see how the speed of
means of a throttle or butterfly valve.
ar" which. when nearly closed, will
allow but small amount OF The mix
When tho throttle is fully opened
however, fun echarse of mixture win
Will 10 powerful. When the explosion
is powerful the piston will be driven
down faster than with the mildor eN-
speed will be greater.
The throttle or butterfly valve is OPP
Grated by n lever on top of the steering
column or by the foot pressing on the
acccicrator. Both OF these, through a
series Of boll-cranks and sliding con
ing il 10 the right or left You will
note that when tho rod IS" is moved
ever ~ tshowm do,Sdi neI rsyol %m , Inc
butterfly valve n i'm a direction on
n,ositc. to tina, shown by the arrow mus
checking tho flow Of the ,nixture while.
when IT is moved 10 the left. it will
open tho butterfly and so let the full
charge reach the cylinders, When we
E!Ve tho engine more gas as the say
ing is we opcn the throttle or butterfly
ms explained above.
How Throttle Affect. Mixture.
WIN this throttle, affect the mixture?
closed. the mixture viii hc checked by
il, and so. sort of pile up in the mixing
..hhameer &C.. and thus greatly reduce
lhc nozzle and the air entering ut ID"
will not be so great II the throttle
s s %ne" i6e s 1merS Wil 10 be greater
will be greater Thc proportion OF gas
as before. because the resistance Of the
opening ID" and the friction OF the
walls VIII tend to check the flow OF the
incoming air more than the resistance
gasoline. Thus, as the throttle is
opened the mixture Will constantly be-
The mixture entering the cylinders
must always be in the same proportion
OF gas and air Therefore tho carbu-
rotor as above will not do. and some
thing must be added TO allow more air
10 enter ut the higher speeds
In most car6uretors This is done, by
which works automatically. Letter
~ shows such q valve. This. YOU
Mltt noie IS he!d against It's seat by
can be adjusted by the screw u;
When there is vacuum in &C" II must
also be in the space w. and under the
valve H Now, = vacuum means an
air pressure less than That Of the at
lnosphere. and rs THO atmosphere is on
;oo OF the valve H" the pressure on
TOP OF II Will be greater than under IT,
and it would tend TO OPEN
Let u suppose that the spring ''S'' is
adjusted so that its pressure would
Just hold the valve closed against the
pressure OF tho atmosphere when the
engine is moving slowly. What would
happen when the vacuum iv ~" is in
creased. as u VIII be when the engine
Is specded up. Why. The valve III"
VIII open, as the spring is not strong
enough TO hold !, closed against the
additional difference in pressure. he
tween tho atmosphere and the vacuum.
thus extra air Will enter the mixing
chamter, and so bring the mixture back
70 the RI Ght proportion. Tho higher
the speed The farther the valve vii!
opsn and Tho more air cnicr.
for the low speed. and Will open SO as
70 give pretty nearly the right mix
lures for the higher speeds but he
saNsc Of the Nar.at:ons in tho spring
always he exactly right for tho higher
speeds. II may be TOO rich or too weak
for this reason most carhUrctors. in
addition 70 a low speed adjustment
srmc this is done by having an extra
Spriug in connection with the auxiliary
Valve, while offers pave a way "a
move tho nrzZlrr needle with the
throttle lever.
Nj carbure;or makers try tn have.
ihe spray as hNc rs possible. as the
nearer 20 mist II leaves the nozzle
The Quicker il Will change TO the case
We saw, n a previous lesson tina, the
decrease as the opening Is made small
or' We also saw that it would in