Arizona republican., 1919-10-19

OIle OIL the IdcLOrS tndL contribute
very largely to the efficiency of the
modern automobile engine is the mani |
fold. As matter of fact the present
types of manifold have been practically |
forced by the degradation of fuel which
has taken place within the past few
years. 1t is peculiarly appropriate, too, |
that we should consider the question of
manifolding just now, when we are
standing on the verge of cold weather,
because it is during the winter that the
manifold exerts its greatest influence
very fine to indulge in the long sweep
ing manifolds that were then the rule.
To get at the bottom of the problem,
we must bear in mind the fact that cold
acts on gasoline just as it does on mo-
lasses-thickens it. With a long mani
fold, where the metal has a chance tol
get cold, the fuel coming in contact
on engine efficiency.
In the now dim past when we got a
very high grade of gasoline it was all
with this cooled area it quite likely to-
become so heavy that instead of gas
eous vapor it it fluid again. When
we got very light, volatile gas this
was not is likely to occur, but with the
present grades. which are not very
much lighter than kerosene, this preci-
pitation is almost certain to occur if
the manifold is long and unheated.
For this reason the modern tendency
in manifold design has been all toward
short passages leading directly. from
the carburetor to the combustion
chambers. The fold curved manifolds
Of the past have practically disap-
peared. Some designers hit upon the
scheme of Incorporating their mani
folds in the cylinder block itself. This
had the advantage of compactness Of
design and, better still. heated the
manifold from it's proximity to the hot
water in the water system.
Today every authority recognizes the
| fact that it is necessary to apply heat
in some form to the inlet manifold in
order to secure efficient VaporiZation
of the gasoline fuel. Many different
ways of achieving this end have been
worked out. One Of the first methods
tried consisted in putting jacket
around the intake manifold at some
| point near the combustion chamber
and passing the heated gases of the
| exhaust around the intake. In this way
the exhaust is make to furnish heat to
I keep the intake manifold at a proper
operating temperature.
A second method consists in boiling
! the carburetor directly to the cylinder
block and over the exhaust passage, SO
that the heat of the latter will keep the
carburetor sufficiently warm to insure
the delivery of light and volatile fuel.
This method is in very general use
now.
There were still other schools of ex-
periments. One insisted that the fuel
must be heated before it reached the
carburetor. Another group heated the
gas in the carburetor itself. The OBJ
vious trouble with both these methods
was the fact that the fuel heated al
such distance from the combination
chamber ran a considerable chance o.
condensing again before it got to the
cylinders. With the constantly decreas
ing quality of our motor fuel this dan
ger became greater.
| 1t is almost obvious that if the fue
must be heated at all it is better t.
perform that operation when it is nea
as possible to the combustion chamber
so the advocates of heating the fue
after it has left the carburetor hav
had the better of the argument.
The most recent designs in manifold
agree in placing inlet and exhaust il
close proximity, so that the heat of tn
latter may be impaired to the fue
keeping the fuel thoroughly vaporize
until it is in the combustion chamber
Some Of these designs place the inle
and exhaust together for a considerabl
distance, while in others the inlet pas
sage simply passes through the exhaus
at a given point. In some construc
tons the inlet passage is actually with
in the exhaust for a certain distance
its metal wall being subjected to tn
heat of the burning gases on thei
way from the cylinders.
Still another recent idea that help
efficient carburetion is the fitting Of
small shutter in the pipe leading to tn
exhaust, so that after the engine is be
the temperature may be regulated 6
the point Of maximum fuel efficienc.
| Last year there was a flood of fut
warming devices known as hot spots
These were heated areas in the inlt
manifold. the fuel passing over whic
was heated and vaporized on its wa
to the combustion chamber Son
commentators on motoring matters IL
formed their readers that the hot sp'
contributed to securing easy startir
in cold weather. 1t requires only
moments thought to realize that IL
hot spot depends on the heat of Il
exhaust for its heating qualities ar
consequently does not get warm unit
the engine has been started for son
minutes. so that its help in startir
is purely imaginary.
Engineers have discovered that viii
our present grades of fuel must
warmed to certain degree to obta.
fuel efficiency, the heat must not
too great or the gas loses so much
volumetric efficiency that the net r,
suit is a power loss which can be
afforded. If the fuel is proper
warmed and is then mixed with co
air the result Is snappy fuel thi
gives a maximum of power. This
the reason for the use of shutter pc
hitting the admission Of cold air aft
the engine has run long enough
reach fair degree Of operating eff
cheney. 1t may be noted, however, tn
with our present grades of fuel there
little likelihood Of too high a degree
heat being reached in cold weather.
The problem of securing fuel eff
cheney is by no means a simple or
Some of the best engineering braii
in the country are engaged on it at Il
present time. There are many diver
factors to be taken into considerable
and each must have due weight. HOY