Early fuel evaporation with bypass

Heating apparatus for the air-fuel mixture of a vehicle engine including a perforated grid placed across the flow of the air-fuel mixture. The grid is spaced downward from the outlet of the carburetor. A bypass housing formed of permeable screen material may be placed with an open inlet end registered with the carburetor outlet and with an open outlet end registered with the face of the heating grid. During engine start and idle modes with or without use of a choke all of the fuel-air mixture passes through the grid. During off-idle engine modes which require substantially greater flow rates, a portion of the mixture may bypass the grid and pass through the permeable walls of the bypass housing.

This invention relates to heating apparatus for the air-fuel mixture of an 
engine and includes a mounting means to permit portions of the mixture to 
bypass the heater when fluid flow demands are relatively large. 
Present regulations established by the Environmental Protection Agency 
reduce allowable unburned hydrocarbon emissions of a vehicle to incredibly 
small quantities as compared with unregulated engines. The previous 
addition of catalytic converters to vehicles effectively reduced these 
emissions. However, emissions of hydrocarbons is still a concern 
particularly during starting and subsequent engine warm-up. During this 
period, the mixture is rich and the carburetor and the engine intake 
passages are cool. Thus, fuel tends to condense thereon and form 
relatively large liquid droplets, rather than forming fine droplets or a 
vaporous mixture. A much leaner mixture might be utilized if the large 
droplets could be eliminated and resultantly hydrocarbon and other 
emissions might be reduced. 
During engine operation and particularly during the engine starting and 
warm-up modes, the mixture entering the engine should be of relatively 
high temperature. As previously stated, fuel that is passing through a 
cool intake manifold tends to condense and to collect. Warming the flow 
prevents this and it is known to use an electrical heater to increase the 
temperature. The specific heater may take many forms yet the basic concept 
is well known. 
The preferred form of heater in the subject application is a perforated 
grid made of a specific ceramic material. The material possesses a 
positive temperature coefficient of resistance. This means that when an 
electrical potential is first placed across the material, the low initial 
resistance of the material permits a relatively large flow of current 
therethrough so as to increase its temperature. As the temperature 
increases, however, its resistance increases so that the material will 
automatically exhibit and maintain a given heating characteristic at a 
given voltage. Each side of the heating grid has a metallic coating which 
form electrical connections to a voltage source and serve to evenly spread 
the electrical potential across the grid thickness. Such a ceramic heating 
grid is disclosed in U.S. Pat. Nos. 4,108,125 and 4,141,327 which issued 
Aug. 22, 1978 and Feb. 27, 1979 respectively. 
The heating grid is normally located across the fluid flow through the 
carburetor outlet and the fluid mixture passes through a plurality of 
openings in the grid. However, in testing a substantial restriction to 
flow has been observed which is objectionable under certain engine modes. 
During testing and development, a grid was placed across the outlet of a 
one barrel carburetor mounted on a 225 cubic inch displacement engine. 
During cruise or wide open throttle modes, engine power losses proved to 
be excessive. The 225 C.I.D. six cylinder engine demonstrated power losses 
as large as 25.2 horsepower at 4400 RPM. A data chart and specification 
list is found at the end of the detailed description and just before the 
claims. 
The subject invention concerns the application of a grid type heater for a 
fuel-air mixture. A bypass means is disclosed in cooperative association 
with the heater to decrease flow restriction during off-idle engine modes. 
During these part throttle and wide open throttle modes only a portion of 
the mixture flows through the heater grid. The remainder flows through the 
bypass. Specifically, the grid is spaced downstream from the outlet of the 
carburetor. In one embodiment, a bypass housing is utilized and 
characterized as a hollow member formed of screen-type material with open 
ends. During starting and the warm-up modes, practically all of the 
mixture passes through the bypass interior defined by the screened housing 
and subsequently through the heater grid. However, when the engine power 
requirements are greater and flow rates increase part of the mixture then 
bypasses the heating grid. In an embodiment utilizing a screened bypass 
housing, large fuel droplets are intercepted during flow through the 
screen. They subsequently collect and pass down the screen to the heated 
grid where vaporization may take place. 
Therefore, an advantageous feature of the subject heater assembly is the 
provision of a heating grid located a spaced distance below the inlet to 
the intake manifold or the outlet of the carburetor so that during engine 
modes requiring low fluid or mixture flow rates substantially all the flow 
is directed to the heater grid. But during engine modes requiring greater 
mixture flows, a substantial portion of the flow passes laterally through 
a bypass means or space between the grid and the carburetor outlet. 
Another advantageous feature of the subject heater assembly is the 
provision of a heating grid having plural flow openings therethrough in 
combination with a bypass mounting which takes the form of a generally 
funnel like member of screen-type material to direct fluid flow to the 
heating grid particularly during start and idle modes of engine operation 
but which permits a portion of the flow to pass directly through the walls 
of the housing during cruise and wide open throttle modes. 
Another feature and object of the subject heater assembly is the provision 
of a heating grid having plural flow openings therethrough which provides 
flow of a fuel-air mixture therethrough in combination with a permeable 
bypass flow housing with its inlet end positioned to receive flow from the 
carburetor and an outlet end positioned to discharge through heating grid 
whereby during engine operation requiring a large fluid flow, a 
substantial portion of the mixture passes directly through the permeable 
sides of the bypass housing. 
Other advantages and objects of the present invention will be even more 
readily apparent from a reading of the following detailed description 
reference being had to the drawings in which a preferred embodiment is 
illustrated.

In FIG. 1, the intake manifold 10 of an internal combustion-type engine is 
illustrated. The manifold 10 defines a passage 12 through which a fuel-air 
combustion mixture passes to the engine cylinders (not shown). The 
manifold 10 supports carburetor assembly 14 which includes a throttle body 
portion 16, a venturi forming main body portion 18 and an air horn or 
inlet portion 20. The throttle body portion 16 includes a pivotal throttle 
blade 22 mounted upon a rotative shaft 24. The throttle blade 22 operates 
to regulate the flow quantity of fuel and air through main passage 26. The 
passage 26 is aligned with a similar passage in a main body portion 18. A 
constricted throat portion 28 in the main body 18 produces a low pressure 
condition therein so that fuel may be drawn and mixed with air flowing 
therethrough. An inlet passage 30 through the air horn portion 20 is in 
alignment with the restricted passage 28. The main body portion 18 also 
includes a fuel bowl forming portion generally indicated by the numeral 32 
and covered by portion 34 of the air horn housing. An inlet fitting 36 
connects by a nut fastener 38 to a conduit 40. The conduit 40 carries fuel 
from the vehicle fuel pump and fuel tank. 
In a conventional manner, a float control inlet valve (not shown) controls 
the discharge of fuel into the fuel bowl portion 32. From fuel bowl 32, 
fuel is drawn through passages to the venturi 28 during off-idle operating 
conditions. During an idle mode of engine operation in which the throttle 
blade 22 is in the closed position shown in FIG. 1, fuel flows from the 
fuel bowl through a separate idle passage where it mixes with air. The 
fuel-air mixture then is drawn downward through the vertical idle well 
passage 42. An opening 44 in gasket member 46 connects passage 42 with a 
space 48. Space 48 is connected to the passage 26 upstream of blade 22 
through a transfer slot or port 50. When the throttle blade 22 is moved 
slightly from the closed position shown in FIG. 1, the fuel and air 
mixture is drawn from space 48 and past the blade 22 for entry into the 
intake manifold 10. 
However, during idle when the throttle blade 22 is in the closed position, 
the mixture passes through a restrictor or orifice 52 which is formed in 
member 54. The flow then passes over the end of a needle valve 56 and 
through opening 58. Needle valve 56 is threadably received by the throttle 
body 16. The end of the needle valve 56 extends through the opening or 
idle port 58 and into the passage 26. During an idle mode of operation, 
mixture passes between the end of valve 56 and the walls of opening 58 to 
control the flow in a regulated manner. The needle valve 56 has a slotted 
head portion 60 so that it can be readily adjusted and a spring 62 is 
placed between the head 60 and the throttle body 16 to maintain the 
threads in snug relation to prevent unintended rotation. It is this 
relative movement between the end of the needle valve and the port 58 
which provides a desired idling mixture. Since the idle system must 
operate for a considerable period of time while the engine is relatively 
cool, a rich idling system is usually necessary. Unfortunately, such 
richness enhances the formation of liquid within the intake manifold 12. 
As previously discussed, this is undesirable. 
The subject fuel delivery system also includes a fluid heater 64 to warm 
the mixture flowing from the passage 26 of carburetor 14. The heater 64 is 
supported by fasteners 66 and 68 which are located at diametrically 
opposite positions as best shown in FIG. 4. The heater 64 is a thin member 
having a generally oval configuration with openings 70 therethrough to 
receive fasteners 66,68. The mid-portion of the heater 64 includes a 
plurality of small openings 72 which permit flow of the mixture passing 
from the carburetor 14 into the intake manifold. The body 74 of heater 64 
is made of positive temperature coefficient ceramic material characterized 
by increased resistance to electricity as temperature increases. Thus, 
initially the resistance is low and a large current will flow through the 
ceramic material to increase the temperature of heater and fluid. As the 
temperature increases, the electrical resistance also increases, which 
automatically limits the electrical current and the temperature obtained. 
To enhance the even flow of electrical current through the thickness of 
the body 74, metallic coating 76, 78 are deposited on opposite flat 
surfaces of the ceramic body 74. 
Referring back to FIG. 1, the electrical connections to the surfaces 76 and 
78 are made by the fasteners 66 and 68 respectively. Fastener 66 is 
metallic and is encircled by a conductive sleeve or spacer 80. The lower 
end of sleeve 80 engages the metallic surface 76 while the upper end of 
the sleeve 80 engages an insulative spacer support member 82. The contact 
between sleeve 80 and fastener 66 connects the surface 76 with a terminal 
member 84 which is supported by the spacer member 82. Terminal 84 is 
connected through a thermal switch assembly 86 to the vehicle battery 88. 
The circuit may also include a vehicle ignition switch. Connector 90 
grounds one side of the battery 88. The lower end of the fastener 66 
extends through without touching the sides of the opening 70 and is 
engaged by a nut fastener 92. An insulative washer 94 prevents contact 
between the fastener 66, member 92 and the metallic surface 78. The other 
metallic fastener 68 extends through an insulative sleeve 96 which engages 
the upper metallic coating 76. A nut fastener 98 engages the bottom 
surface and metallic coating 78 of the heater assembly 64. At the upper 
end of fastener 68, a terminal member 100 is supported between spacer 
member 82 and intake manifold 10 to ground this side of the circuit. Also 
a conductive member 102 may be attached between ground and the terminal 
100. 
The fuel-air mixture from passage 26 of the carburetor flows directly to 
the heater during an idle or start mode of operation. The spaced placement 
of the grid 74 directly below and in line with the opening 26 directs 
substantially all of the flow toward the heater when flow rates are 
relatively low such as during starting and idle. At other times, some 
portion of the flow bypasses the grid 74 and flows laterally with respect 
to the downward idle flow. In an embodiment utilizing a generally 
conically shaped housing 104, the flow is more forcefully guided to the 
grid. However, at higher flow rates, a portion of the flow does pass 
through the walls of the housing 104. The member 104 is made up of a 
screen-type material preferably of stainless steel-type, copper or plastic 
material such as nylon. The side surfaces of the housing are permeable to 
fluid flow. An upper end has an outwardly turned flange portion 106 which 
rests upon an inner edge 108 of member 82. A radially extending head 
portion 110 of fastener 66 holds the portion 106 of housing 104 to the 
terminal 84 and the spacer member 82. A similarly formed portion 112 of 
fastener 68 holds the opposite portion 106 of the housing 104 to spacer 
member 82. An insulative washer member 114 extends between the head 
portion 112 and the portion 106 of the bypass 104 to prevent electrical 
contact between flange 106 and fastener member 68 and thus shorting of the 
grid heating circuit. 
The lower end of the bypass housing is open at 116 and aligned with the 
apertured portion of heater 64 so that fluid passing through the housing 
interior is directed through the many openings 72 as can be seen in FIG. 
2. During a starting or idling mode of engine operation, a substantial 
portion of the mixture passes through the grid heater. During start and 
idle modes, the flow required for engine operation relative to other 
operative modes is relatively low so that practically all the air-fuel 
mixture will pass through the openings 72 of the heater 64. When the 
engine is operated at cruise or wide open throttle modes of operation, the 
throttle blade 22 is moved from the closed position shown in FIG. 1 and 
the fluid flow is increased substantially. If all this greatly increased 
flow were to pass through the grid openings 72, the flow restriction would 
greatly reduce the engine power and performance. As previously mentioned, 
tests conducted with a 225 C.I.D. 6 cylinder engine equipped with a single 
barrel carburetor revealed a power loss of about 30% at higher RPMs when 
the air-fuel mixture had to first pass through the grid heater 64. 
Utilizing the bypass housing 104 between the carburetor 14 and a downwardly 
spaced heater grid 64, the aforementioned large power losses were 
practically eliminated. During the off-idle engine modes when the fluid 
flow through the carburetor increases greatly, a large portion of the flow 
passes through the permeable walls of the bypass 104. Meanwhile, a 
relatively small portion of the flow passes through the openings 72 in the 
heater grid 64. Resultantly, the flow restriction at off-idle is 
substantially decreased. It should be noted that the flow area through the 
screen-type walls of member 104 is large compared with the flow area 
through the passages 72 due to the geometry including the large continuous 
side surface of the member 104. The data hereafter indicates that a 225 
C.I.D. engine with a bypass produced only about 3% less power than a 
standard 225 C.I.D. 
An advantage of providing the screen sided housing 104 is the ability 
thereof to intercept rather large fuel droplets before their entry into 
the intake manifold 10. These droplets collect and combine to form a 
substantial quantity of wasted liquid fuel. With housing 104, the droplets 
are directed downward and along the screen until reaching heater 64. Upon 
contact with the grid, the fuel droplets quickly vaporize and are picked 
up by air passing therethrough. Tests on a vehicle having a 225 CID engine 
with a single barrel carburetor disclosed substantial reductions in engine 
start-up times and reductions in CO under power. 
Although only a single embodiment of the invention has been illustrated in 
the drawings and another without the screen housing but otherwise as shown 
has been described, modifications and other embodiments will easily occur 
to persons skilled in the art, which modifications would still fall within 
the scope of the following claims which solely define the invention to 
which an exclusive property right is asserted. Particularly, other heater 
and housing support arrangements are possible and other electrical 
connection makers are contemplated. 
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Test Specifications 
Test Engine #1 - 
In line 6 cylinder Chrysler engine of 
225 CID carburetor: 1.67 inch diameter single 
bar 
Test Engine #2 - 
Same engine and carburetor as #1 
Heater Grid - overlying outlet of carburetor 
Test Engine #3 - 
Same engine and carburetor as #1 
Heater Grid - .375 spaced from the manifold 
intake 
HORSEPOWER 
RPM #1 #2 #3 
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1200 37.0 34.3 34 
1600 50.0 44.8 47 
2000 62.5 54.5 58 
2400 74.0 63.1 68 
2800 82.6 68.8 77 
3200 89.0 71.3 84 
3600 91.2 72.0 87.5 
4000 89.9 68.5 88 
4400 83.8 58.6 83 
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