El Paso herald. (El Paso, Tex.) 1901-1931, 1918-05-25

MOT least among the factors that
N contribute TO the relative eff
cheney Of the modern motor car as
compared with its predecessors Of a 1
few years ago, is the present day de-
sign OF manifolds. The efficiency Of I
the manifold has much to do with
carbura ton efficiency, and this in
turn largely determines the power, !
economy. etc. Of the engine. No other /
Fart Of the internal combustion en-
CINE has undergone quite such revo- I
lutionary changes within the past few
years as the manIfolds, especially the
inlet.
Two considerations have forced
manifold design on 4 attention or
the engineers One has been the in
sistent demand Of the motoring pub /
lie, ever since there has been such ]
thing, for economy Of operation as re-
CARDS fuel and secondly the declining
quality Of the gasoline that we have
been getting.
In the days when we got highly
volatile fuel that exploded without
announcement Of any kind we could
afford 70 use long exposed manifolds,
because the snappy gas Of that time
had little tendency to condense on us
way 70 the cylinders. The long mani
folds Of Yesterday had certain merits,
principally their lack OF sharp curves
which would interrupt the flow OF
gas But their length and exposed
position would make them Impossible
with present day grades Of fuel
Perhaps the average car owner does
not know. or rather does not stop 10
think. just what process the fuel goes
through before 10 reaches the COM
bustfOn chamber The fuel flows from
the gasoline tank, through pipe into
the carbureter, either directly OF via
a vacuum tank The fuel enters the
float bowl Of the carbureter. where II
passes through a very small opening
The partial vacuum that is created IN
the cylinders by the movement OF the
piston. lifts the fuel into the com
bustiOn chamber. Now II the fuel Is
very light and highly explosive, It
flows into the combustion chamber
without trouble. But when Ii is
heavy. it does not flow readily. its
rate Of flow decreasing as its weight
Increases. Everyone knows that cold
tends 10 thicken oil Of any kind, gaso-
line as weu as others. A fairly good
grade Of fuel may leave the carbu-
refer pretty well volatilized. but
striking a cold surface, as the metal
Of an exposed manifold, IL viii con-
dense on the walls and relatively
little OF Il will reach the combustion
chamber. This is the problem our en-
gineers have endeavOred TO solve.
One Of the first methods Of improv-
ing the manifold was that Of putting
q jacket around the intake section at
some position rear the cylinders and
passing either heated bases or hot
water around the manifold Another
method was tried little later Of bolt
ing the carbureter directly 10 the
cylinder block, so that the heated gas
passage in the casting would supply
/ heat enough TO vapOrize the fuel This
latter method is uavd to great ex-
tent now.
One school Of designers tried the
experiment Of heating the fuel before
it reached the carbureter- Still an
( other group favored the idea Of heat
ing the gasoline right in the carbu-
reter. Both these methods had GER
tain Disadvantages, from the fact that
If fuel is heated before Il gets to the
] carbureter or even in that instrument,
IL still has an excellsnr chance Of con-
/ densinE again on its way from the
/ carbureter to the combustion chamber,
| unless additional means Of keeping II
warmed is provided. If this latter Is
Z done why not perform the whole op-
GRAFTON after the gasoline has left the
] carbureter2
In a number Of recent designs the
I inlet and exhaust manifOlds have been
[ placed in close juXtaposition. with the
D intention OF having the uedLeu Ea9el
I in the latter impart enough warmth
I to the former to keep the fuel thor
I oughly vaporized. In similar designs
I the inlet manifold Is made to pass
/ through the exhaust outlet at single
point While these designs seem TO
give satisfaction. probably the most
! efficient method OF handling the PROB
l lem is found in the idea Of incorpor-
ating the inlet manifold within the
cylinder block. where ii is practically
( surrounded by a hot volume and Is
close 70 parts that ordinarily run not
Another idea that contributes to e1-
ficfent carburetion is found IN the
fitting OF the air pipe leading 10 the
exhaust nine with a movable shutter
I whereby after the engine is hot, the
/ shutter may be opened TO admit colo
air. so as to obtain exactly the right
! conditions for maximum fuel enc
I iency.
/ Last year there was violent r.
ruptIon OF manifolds commonly called
] 'bot spots" The name was accurate
I " descriptive for it simply means a
] spot in the inlet manifold maintained
/ al a high temperature so that the gas
I i'm passing over Il is warmed and mace
I highly volatile. IL is peculiar faci
] that vaporized fuel does not take the
/ same course as liquid fuel. Gas OF