US3491534A - Exhaust manifold - Google Patents

Description

w. 1.. GARNER 3,491,534

EXHAUST MANIFOLD Filed April 24, 1968 Jan. 27, 1970 United States Patent US. Cl. 60-32 14 Claims ABSTRACT OF THE DISCLOSURE An exhaust system for multi-cylinder internal combustion engine having a plurality of exhaust ports including a plurality of elongate exhaust tubes having forward and rear ends, means connecting forward ends of the tubes to an engine in communication with ports therein, an elongate collector having front and rear ends, a central, cylindrical, longitudinal outlet bore entering its rear end, a plurality of elongate, cylindrical inlet bores entering its forward end, means connecting the rear end of the tubes to the collector with each in communication with an inlet bore, the cumulative cross-sectional area of the inlet bores being greater than the cross-sectional area of the outlet bore, said bores converging rearwardly and radially inwardly to establish communication with each other and with the outlet bore, and defining a rearwardly convergent chamber with fluted side walls, the flutes defining outer segmental extensions of the tubes to contain or prevent radial outward and circumferential expansion and defusion gases flowing from the tubes, said converging bores defining a central rearwardly convergent stem in the chamber having concaved surfaces defining extensions of the inner portions of the tubes to contain and control radial inward and circumferential expansion of gas flowing from the tubes whereby the streams of gas are directed radially inwardly and rearwardly to converge with each other forward of the outlet bore and to react with and direct each other centrally rearwardly into and through the outlet bore as a single stream of gas, venturi means at rear ends of each tube to bean the flow of gas so that back pressure at the forward end of each tube is substantially equal to the back pressure at the forward end of each other tube and to accelerate the gas flowing therefrom whereby the inner inertia thereof induces and maintains flow of gas through and from the tubes, said chamber and outlet bore defining a venturiwhereby the gas flowing through and from the collector is accelerated and the mass inertia thereof induces and maintains the rearward flow of gases into, through and out of the system.

This invention has to do with an exhaust system and is particularly concerned with an exhaust system for automotive type internal combustion engines.

The ordinary automotive type multiple cylinder, reciprocating, internal combustion engine is provided with a valve controlled exhaust port related to each cylinder and through which products of combustion or exhaust gases are exhausted during operation of the engine.

Except in rare instances, engines of the type or class here concerned with are provided with exhaust systems to collect and conduct the exhaust gases away from the engine and exhaust it into the atmosphere at a location remote from the engine.

The ordinary conventional exhaust system, as found in automobiles and the like, includes an exhaust manifold related directly to the engine and communicating with the exhaust ports therein, or two or more of such manifolds in the case of engines having two or more banks or related series of cylinders, a header pipe of high heat re- 3,491,534 C6 Patented Jan. 27, 1970 sistant tubing extending from the manifold, or manifolds, and an elongate tail pipe or tail pipe assembly fixed to the header pipe and extending to the location where the gases are to be exhausted.

The tail pipe assemblies normally include canister type mufflers.

The ordinary exhaust manifold is a unitary cast iron log type manifold having a single outlet port to connect with a related header pipe and a number of lateral tubular branches with mounting flanges, extending to the engine to communicate with the exhaust ports and bolted in fixed relationship therewith.

The ordinary exhaust system, as set forth above is very familiar to those skilled in the art.

It is well recognized that the exhaust system for an engine greatly affects the efficiency of the engine. If properly designed an exhaust system affords a predetermined back pressure, which is equal at each exhaust port and allows for the freest possible flow of gas from the engine, thereby affording little adverse effect upon engine operation and efficiency. If, on the other hand, such a system is not properly designed, and affords considerable back pressure unequal at the several exhaust ports, and does not allow for free flow of exhaust gases, it materially, adversely affects the operation and efficiency of its related engine.

It has become well-recognized that the ordinary unitary, cast iron, exhaust manifold provided as stock equipment by practically all manufacturers of automotive engines is a most unsatisfactory unit and results in considerable interference with proper engine operation or function and results in great loss of efliciency.

As a result of the above, when maximum performance and efficiency is demanded of an engine, as in high performance and racing engines, special exhaust systems are provided and are substituted for the standard or stock exhaust systems. Such systems, commonly referred to as headers, include a separate exhaust pipe or tube provided for each exhaust port of their related engines, a collector receiving gases from the several tubes and a tail pipe connected with the collector. Header systems such as referred to above are designed and intended to allow for the gases exhausted through each exhaust port to flow as independently as is practical for the exhaust gases issuing from the other exhaust ports and to flow as freely as is possible. That is, their function is to prevent cross interference of the gases flowing from the several ports and to create as little adverse back pressures as is possible.

One of the most recent developments in header design is to make all of the exhaust tubes equal in diametric and longitudinal extent and so that the back pressure on each cylinder of the engine, afforded by the exhaust system is substantially equal. This special feature, in some cases, has been amplified upon by making the several exhaust pipes a predetermined length so that, at a predetermined speed where the pulsation in the tubes is at a predetermined rate, the tubes are harmonically tuned so as to induce the desired flow rate of gases therethrough.

While the above header systems have proven to be a major advance in the art, over the standard or stock systems with cast iron manifolds, they still fail to function as effectively and efficiently as is desired.

A principal shortcoming found in the ordinary header type system is to be found at the collector, where the several exhaust tubes join and the gases flowing therethrough converge or join for subsequent flow into and through the tail pipe. The ordinary collector is a simple, elongate, unitary part defining a chamber and having a plurality of inlet openings at one end to connect with the exhaust tubes and a single outlet opening at its other end to connect with the tail pipe. Such a simple or basic concept fails to take into proper account the ttlrbulence and back pressures created at or in such collectors and the ultimate effect of such turbulence and back pressures at the exhaust ports.

While .the inherent elastic and/orresilient nature of the columns or flow streams of gases flowing through the exhaust tubes, from the ports to the collectors buffers and smoothes out much of the interference created by the 7 collectors, it has been found that the collectors create such an overwhelming amount of interference with the flow of gases from the engines that the, operation and efiiciency of the engines are adversely affected.

In the case of those header systems where theseveral exhaust tubes are the same length, great difiiculty is found in forming the tubes and in finding adequate space about the engines and within the engine compartments to accommodate the system of tubes. Further, in practice, each such. tube is bent and formed in a different manner and to a different extent than each of thej 'other tubes, with the result that though the tubes are the same length, the friction loss and resulting back pressure, created by bending and turning the columns or flow streams of gases through the tubes, creates back pressure dilferentials at the exhaust port ends of the several tubes, with the result that the advantage which isisought and supposed to have been gained, is lost. 7 7

An object of my invention is to provide a novel and improved header type exhaust system wherein the several exhaust tubes are of varying length, are bent and formed to take the straightest and freest path from their related ports to a common collector and wherein each tube is provided with flow restricting means at its discharge end (remote from it's inlet end and related exhaust port) to create a predetermined back pressure at its inlet end whereby the several tubes are tuned to create substantially equal back pressures at their inlet ends.

Another object of the present invention is to provide a novel system of the character referred to having a novel collector designed to induce free and uniform flow of gases from the severalrelated exhaust tubes, through and from the collector.

Yet another object of my invention is to provide a system or structure of the character referred to wherein the flow restricting means at the discharge ends of the exhaust tubes are in the nature of venturi and serve to accelerate the flow of gases issuing from the tubes into the collector and serve to direct the flow of gases through the collector. It is yet another'object of my invention to provide a structure of the character referred to wherein the flow of gases flowing through the exhaust tubes is pulsatingand the several tubes related to the collector discharge pulses of gas sequentially and in such a manner that each pulse ZOf gas from each tube is accelerated and directed into and through the collector scras to create a minus pressure within the collector about the discharge ends of the other tubes to induce and maintain an outward flow of gases in said other tubes and to, in efiect, scavenge gases from said other tubes, thereby reducing back pressures in the system.

Still another object of the present invention is to provide venturi means at the discharge end of the collector whereby the gases are accelerated as they flow therefrom and into the tail pipe whereby the mass inertia of the collective and accelerated mass of gases issuing from the collector induces and maintains a substantially uniform flow through the collector and scavenges gases from the collector to further increase the efficiency of the exhaust system.

Another object of my invention is to provide a system of the character referred to which requires a minimum of easy and economical to manufacture parts and a system wherein the several elements and/or parts are separable and such that they can be easily, quickly and economically assembled without the exercise of special skills and without the use of special tools and equipment.

It is an object of this invention to provide an exhaust 4 system of the character referred to which is, such that it can be easily, conveniently and economically designed and tuned for most efficient operation for any make. and

.design of automobile engine, chassis and body with which 5 it might be related.

The foregoing and other objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of my invention, throughout which description reference is made to the accompanying drawings, in which:

FIG. 1 is an elevational view of my new exhaustrsystem, showing it related to a. portion of an engine;

FIG. 2 is sectional view taken as indicated by line 22 on FIG. 1;

FIG. 3 and FIG. are sectional views taken as indicated by lines 33 and 44, respectively, on FIG. 2; and, '7 n FIG. 5 is a sectio "a1 view of a portion of arthird form of my invention. a

The exhaust system A illustrated in FIG. 1 of the accompanying drawings is shown related to a head H of, for example, the right hand,cylinder bank of a 1968, 289 or 302 cubic inch Ford V-8 engine E. It is to be understood that, in practice, the configuration of the tube parts is varied widely to adapt the construction for use on other ,makes and models of automobile engines, without departing from the spirit of this invention.

The system A is shown as including, generally a plurality of elongate exhaust tubes T having ihlet and outlet ends, a collector C and an exhaust or tail pipe P. s

The several exhaust tubes T are simple, elongate tube members and are provided at their inlet eiids with flanges 10 to facilitate fixing the inlet ends of the tubes to the engine head H by means of bolt fasteners 11 and in connection with e xhaust ports (not shown) in the head.

The above relationship of tubes, tube flanges, bolts, heads and exhaust ports is well known in the art, is not in itself novel and is subject to some well known and accepted variations. Accordingly, I will not burden this disclosure with further unnecessary, detailed description of this portion of my construction.

The several tubes T extend downwardly and rearwardly to terminate in substantial juxtaposition with their outlet ends in a common vertical plane.

It will be apparent that the tube connected with the forward end of the head is substantially longer than the tube connected with the rear end of the head and that the two intermediate tubes are of differing and intermediate lengths. It will also be apparent that as a result of the relative spacing and arrangement of the ends of the sev- .eral tubes, those bends which occur in the tubes are different.

It is to be understood that the header assembly related to the other or left-hand cylinder bank of the engine is not necessarily identical to that assembly illustrated, but, in fact, is quite different and in the case of a 1968 289 or 302. cubic inch Ford V-8 engine, the tubes are bent and formed in a more irregular manner and vary in l ngth to a greater extent.

The several tubes T are the same in diametric extent.

In addition to the foregoing and in the first form of the invention, the discharge ends of the tubes T are provided with venturi nozzles N. The nozzles N are radially inwardly and rearwardly inclined, truncated conical nozzles estab- 55 lished by suitably forming extensions on the tubes.

The nozzles on each tube can be different in minor diameter than the minor diameter or the nozzle on each of the other tubes and is adapted to, first, create a predetermined back pressure in the tube, at its inlet end and,

second, to accelerate the rate of flow of the gases issuing from the tube. The beaning down of the flow of gases in the tube, by the venturi nozzle N, in addition to creating the desired back pressure, also tends to buifer or modulate the pulsation of the stream of gases and causes the pulses to lengthen slightly, in duration, at the discharge end and in and through the venturi, thereby including a more regu- :Iar flow of gases through and out of the nozzles N.

In practice, the size and beaning effect of the nozzles can be established for each different size, shape and length of tube and for each exhaust port on each make and model of engine by means of a test apparatus or test engines with which test tubes are connected and which delivers into and through the. tubes predetermined volumes,

of gas, at predetermined rates of pulsation and at predetermined pressures. With gases thus being conducted into and through the tube and by means of a pressure gauge related to the inlet end of the tubes and/or by means of flow rate measuring means related to the discharge ends of the tubes, the sizes of the nozzles can be established.

Each of the nozzles N, on the several tubes, is established so that the back pressures at the inlet ends of the several tubes are substantially the same.

In the event the beaning effect of the nozzles N, at different engine speeds, creates excessive dilferences in the sought-after back pressures, the nozzles should be set for that speed or range of speeds in which greatest efficiency is desired. In practice, it is normally desired to seek the sought-after efliciency at high engine speeds, which are within a known or established range and where the efli ciency of an exhaust system becomes most critical. Further, such a system is generally more than adequate for low and medium engine speeds and the efficiency here sought to be obtained is of little or no importance. Accordingly, concern about variations in back pressure caused by the beaning efiect, mentioned above, is of academic interest only.

The collector C is an elongate, unitary cast metal part having flat, radially extending, axially forwardly and rearwardly disposed front and rear ends 20 and 21, a central longitudinally extending, rearwardly opening exhaust or outlet bore 22 and a plurality of elongate, axially extending, forwardly opening inlet bores 23 spaced circumferentially about the central longitudinal axis of the collector. The outlet bore is, for example, two inches in diameter and the inlet bores are 1 /2 inches in diameter, with the result that the cross-sectional area of the single outlet bore, being 3.1416 square inches, is somewhat less than one-half the cumulative area of the four inlet bores, which is 7.068 square inches.

The inlet bores have straight, longitudinally extending, forward portions and curved or inclined rear end portions which are turned radially inwardly and rearwardly towards the central longitudinal axis of the collector to converge and communicate with the forward end of the outlet port. The angle of intersection of the inlet ports with the outlet ports is preferably slight and should not exceed thirty degrees, so that the inlet bores, in eflect, fare smoothly into the outlet bore.

The radial inner portions of the inlet bores, near the central axis of the collector, converge with each other forward of the forward end of the outlet bore to define an open central collector chamber X. The chamber X being established by the four intersecting circular inlet bores is defined by a fluted outer wall and is somewhat clover shaped in cross-section. The chamber X has a central rearwardly projecting, rearwardly convergent, polygonal flow directing stem 25 in its forward portion. The sides or surfaces 26 of the stem are concaved and are disposed towards related fluted portions of the outer wall of the chamber.

The fluted wall of the chamber X establish four radially inwardly projecting, circumferentially spaced, longitudlnal- 1y extending, flow directing, rib-like vanes 27 the inner edges 28 of which are tangential with and fare into the wall of the outlet bore.

The forward ends of the straight forward portions of the inlet bores are bored out and enlarged to define forwardly The body of the collector, at the forward end thereof is provided with a pair of diametrically opposed outwardly opening threaded openings 30, which openings extends between and intersect two of the sockets 29 and in which retaining screws 31 are engaged to engage and retain the header tubes T. The openings 30 intersect the sockets 29 on cord lines sufficiently deep so that the threads of the screws 31 engage and bite into the tubes T,.but not so deep as will cause collapsing and adverse deformation of the tubes.

With the retaining means set forth above and comprising the openings 30 and fasteners 31, it will be apparent that two screws effectively maintain the collector C and the four tubes T assembled and that no welding and no use of special tools and equipment is required to make up the noted connection or connections.

In practice, stop means Y, such as simple metal t-abs spot welded to the tubes T and adapted to engage the rear end of the collector and limit engagement of the tubes therein can be provided.

It is to be noted that the rear end portion of the collector in which the outlet bore and the chamber X occur, establishes and defines a secondary venturi nozzle V,

which nozzle serves to accelerate gases issuing from the nozzles N and further accelerates the accumulated or collected mass of gases and discharges it, at increased velocity, rearwardly and from the open rear end of the outlet bore 22.

The concaved and radially inwardly curved flutes of the inner surface of the side wall of the chamber X related to each tube T and/or inlet bore 23 direct the gases issuing from the tube, radially inwardly and rearwardly towards and into the outlet bore. The longitudinal vanes 26 defined by the adjacent sides of adjacent flutes serve to retain the flow stream of gases and prevent the stream from expanding and spreading excessively as it moves rearwardly in the chamber and in such a manner as to create adverse turbulence.

The concaved surface 26 of the stem 25, related to each fluted portion of the chamber surface, directs the column or stream of gas rearwardly into the rear end portion of the chamber and, thence, into the outlet bore and prevents and/or inhibits premature radial inward expansion of the gases, in the chamber which would otherwise create turbulence in the forward portion of the chamber, which would slow and/or impede the rearward flow of gases in and through the chamber and into the outlet bore.

The pulsating flow stream of gases issuing from each tube T and flowing through the collector is eflectively directed and contained within the collector so that its work energy is not spent in random turbulence, but rather, is controlled and directed in such a manner as to react on and with the flow stream of gases issuing from each of the other tubes in such a manner as to induce and maintain a smooth, substantially uniform and positive rearward movement of gases in and throughout the construction.

The positive pressure pulses of the several flow streams of gases flowing into the collector from the tubes T and nozzles N, occur sequentially and combine in the outlet bore to impart a pulse rate of four times that of each of the inflowing streams of gases. This results in the application of three negative or minus pressure pulses to each inflowing stream of gas between each positive pulse of said inflowing stream, which application of negative pulses induces the rearward flow of gas through and out of the tubes and nozzles N.

The mass inertia of the several accelerated and controlled inflowing streams of gases and the mass inertia of the accelerated, controlled and combined outflowing stream of gases, into, through and from the collector,

create minus pressures at the nozzles N and V which effectively draw and scavenge the gases in the tubes T to reduce back pressures therein and maintain a most eflicient flow rate therethrough.

The tail pipe P can be of any desired form and construction.

In the form the invention now under consideration, the pipe P is a simple length of pipe or tubing with inlet and outlet ends 40 and 41 and has a mounting flange 42 at its forward or inlet end to establish flat bearing and sealing engagement with the flat rear end of the collector. The flange is shown fixed to the collector by means of suitable bolt fasteners 43.

In practice, a gasket 42 is arranged between the flange 40 and collector.

In practice, and as illustrated in phantom lines in FIGS. 1 and 2, the tail pipe can be in the nature of a rearwardly divergent, conical or horn-like pipe in the nature of an extension of the venturi nozzle V and through which the gases flow and expand in a controlled manner for subsequent exhaust into the atmosphere.

In FIG. 5 of the drawings, I have shown a portion of the collector C with a different form of tube T and nozzle N related to it. 3

In this second from of the invention, the tube T and nozzle N are separate parts. The nozzle N is an annular insert engaged in and seated on the bottom of its related socket 29 and the rear end of the tube T is engaged in the socket and against the nozzle insert to hold and maintain the insert in place.

With this form of the invention, the tubes need not be specially made.

Further, varying, changing or tuning of the system is made possible by providing sets of inserts of varying sizes which inserts can be changed as circumstances require or as desired. Such an arrangement or set-up may be extremely desirable for tuning and preparing a race car engine for use in different environments and for different use. For example, tuning the exhaust system of a race car engine for use or operation on a relative low speed race course at high altitudes and next tuning the same engine for operation on a high speed course at low altitudes.

Also, in this second form of the invention the rear end of the outlet bore 22 is provided with an enlarged socket 50 in which the forward end of a flangeless tail pipe P is slidably engaged and seated. The pipe P is retained by a screw fastener 51 engaged in the collector laterally of the longitudinal axes thereof and with its threads engaging in the exterior of the portion of the pipe P engaged in the socket 50.

In practice, if desired and as shown in phantom lines in the second form of the invention, the forward end portion of the outlet bore, where the fluted walls 23 of the chamber X join with the bore, the bore can be formed with an aerodynamically curved venturi throat which fares smoothly into and with the walls of the chamber and which opens or enlarges as it extends rearwardly and to the inside diameter of the tail pipe. Such an arrangement is particularly adaptable for incorporation in a system wherein a simple, straight tail pipe is employed, but is of no advantage in a system wherein a rearwardly divergent, tuned horn-type tail pipe, such as is shown in phantom lines in FIGS. 1 and 2 of the drawings is employed and where the tail pipe constitutes an extension of the venturi.

In practice, that tube T or T which affords the greatest back pressure can be a straight through tube, that is, without a flow bearing means or venturi nozzle related to it. The remaining three tubes are then provided with beaning means or nozzles so that each affords the same back pressure as the single straight through tube.

It is to be noted that the differentials in flow characteristics in the several tubes is not extreme, but is rather slight and the extent of beaning required to balance the tubeS in @QCQItlance with my invention, is slight.

In practice, if the tubes are initially tuned and balanced so that their flow characteristics are the same, without the requirement of using beaning means such as referred to above, the flow beaning means can be eliminated, in which case the collector still functions to collect and effectively and efliciently combine the several inflowing streams of gas and the venturi effect of the chamber and outlet bore still functions to induce and maintain the flow of gas through the system.

Further, even though the tubes may be initially balanced and tuned, the provision of the nozzles N may still be employed as venturi to accelerate the rate of flow of the gases in and through the collector to increase the mass inertia of the streams of gases issuing from the nozzles and to induce and maintain the desired flow of gases into, through and from the tube, and, further, super-charging and enhancing the venturi action afforded by the venturi V defined by the chamber and outlet bore.

Having described my invention, I claim:

1. An exhaust system for a multi-cylinder, internal combustion engine having a plurality of exhaust ports including a plurality of elongate exhaust tubes having forward inlet and rear outlet ends, means connecting the forward ends of the tubes to an engine in communication with ports therein, an elongate collector having front and rear ends, a central, cylindrical, longitudinal outlet bore entering its rear end, a plurality of elongate, cylindrical, forwardly opening inlet bores entering its forward end, means connecting the tubes to the forward end of the collector with each in communication with an inlet bore, the cross-sectional area of the inlet bores and tubes beng substantially equal, the cumulative cross-sectional area of the inlet bores being greater than the cross-sectional area of the outlet bore, said inlet bores extending longitudinally rearwardly and radially inwardly in the collector to converge and establish communication with each other and with the outlet bore, said convergent inlet bores converging to define a rearwardly convergent collector chamber with concaved fluted side walls, the flutes of said side wall defining outer segmental, longitudinally rearwardly and radially inwardly extending extensions of the tubes related thereto and contain or prevent radial outward and circumferential expansion and diffusion of the outer portions of the streams of gases flowing from the tubes and radially inwardly and rearwardly in the collector, said converging inlet bores defining a central longitudinally rearwardly convergent stem in the forward end of the chamber having concaved substantially radially outwardly disposed surfaces defining extensions of the radial inner portions of the tubes to contain and control radial inward and circumferential expansion of the radial inner portions of the streams of gas flowing from the tubes and radially inwardly and rearwardly in the collector whereby the streams of gas are directed radially inwardly and rearwardly to converge with each other forward of the outlet bore and so that they react with and direct each other centrally rearwardly into and through the outlet bore as a single stream of gas, said chamber and outlet bore define a venturi whereby the gas flowing through and from the collector is accelerated and the mass inertia thereof induces and maintains the rearward flow of gases into, through and out of the system.

2. A structure asset forth in claim 1 wherein the side portions of adjacent flutes of the side wall of the chamber define circumferentially spaced, radially inwardly projecting, longitudinally extending and rearwardly convergent vanes with substantially straight, longitudinally extending radial inner edges substantially tangential with and faring into the forward end of the outlet bore.

3. A structure as set forth in claim 1 wherein the means connecting the tubes and the collector comprise sockets in the forward end of the colector, concentric with the inlet bores and in which the rear ends Of the tubes are slidably engaged.

4. A structure as set forth in claim 1 wherein the means connecting the tubes and the collector comprise sockets in the forward end of the collector, concentric with the inlet bores and in which the rear ends of the tubes are slidably engaged, and screw fasteners engaged in the collector to extend laterally between adjacent pairs of sockets and with their threads engaging the exteriors of the rear portions of the tubes therein.

5. A structure as set forth in claim 1 wherein the several tubes are the same in cross-section, are of different length and are provided with dissimilar bends, said structure further including flow beaning means adjacent the rear ends of the tubes whereby the back pressure and flow rate of gases at and through the forward inlet ends of the several tubes is substantially equal.

6. A structure as set forth in claim 1 wherein the several tubes are the same in cross-section, are of different length and are provided with dissimilar bends, said structure further including flow beaning means adjacent the rear ends of the tubes whereby the back pressure and flow rate of gases at and through the forward inlet ends of the several tubes is substantially equal, said flow beaning means includes rearwardly convergent flow constricting nozzles in the inlet bores and at the discharge ends of the tubes.

7. A structure as set forth in claim 1 wherein the several tubes are the same in cross-section, are of different length and are provided with dissimilar bends, said structure further including flow bearing means adjacent the rear ends of the tubes whereby the back pressure and flow rate of gases at and through the forward inlet ends of the several tubes is substantially equal, said flow beaning means includes rearwardly convergent flow constricting nozzles in the inlet bores and at the discharge ends of the tubes, said nozzles being venturi nozzles and serve to accelerate the rate of flow of gas into and through the chamber, the mass inertia of which induces and maintains the flow of gas into, through and from each tube and which supercharges and enhances the function of the venturi defined by the chamber and outlet bore.

8. A structure as set forth in claim 1 wherein the several tubes are the same in cross-section, are of different length and are provided with dissimilar bends, said structure further including flow beaning means adjacent the rear ends of the tubes whereby the back pressure and flow rate of gases at and through the forward inlet ends of the several tubes is substantially equal, said flow beaning means includes rearwardly convergent flow constricting nozzles in the inlet bores and at the discharge ends of the tubes, said nozzles being formed integrally on and with the rear ends of the tubes and occurring in the rear portions of the inlet bores.

9. A structure as set forth in claim 1 wherein the several tubes are the same in cross-section, are of different length and are provided with dissimilar bends, said structure further including flow beaning means adjacent the rear ends of the tubes whereby the back pressure and flow rate of gases at and through the forward inlet ends of the several tubes is substantially equal, said flow beaning means includes rearwardly convergent flow constricting nozzles in the inlet bores and at the discharge ends of the tubes, said nozzles being annular inserts engaged in the forward portions of the inlet bores adjacent the rear discharge ends of the tubes.

10. A structure as set forth in claim 1 which further includes an elongate tail pipe with front inlet and rear outlet ends and means connecting the front end of the tail pipe to the rear end of the collector with the pipe in communication with the outet bore.

11. A structure as set forth in claim 1 which further includes an elongate tail pipe with front inlet and rear outlet ends and means connecting the front end of the tail pipe to the rear end of the collector with the pipe in communication with the outlet bore, the forward end of the tail pipe being substantially equal in inside diameter with the outlet bore and diverging rearwardly to define a rearwardly divergent expansion portion of the venturi established by the chamber and outlet bore.

12. A structure as set forth in claim 1 which further includes an elongate tail pipe with front inlet and rear outlet ends and means connecting the front end of the tail pipe to the rear end of the collector with the pipe in communication with the outlet bore, and flow beaning means including rearwardly convergent flow constricting nozzles in the inlet bores and at the discharge ends of the tubes.

13. A structure as set forth in claim 1 which further includes an elongate tail pipe with front inlet and rear outlet ends and means connecting the front end of the tail pipe to the rear end of the collector with the pipe in communication with the outlet bore, the for-ward end of the tail pipe being substantially equal in inside diameter with the outlet bore and diverging rearwardly to define a rearwardly divergent expansion portion of the venturi established by the chamber and outlet bore, and venturi nozzles at the outlet ends of the tubes and serving to accelerate the rate of flow of gas into and through the chamber, the mass inertia of which induces and maintains the flow of gas into, through and from each tube and which super-charges and enhances the function of the venturi defined by the chamber and outlet bore.

14. A structure as set forth in claim 1 which further includes venturi nozzles in the forward portions of the inlet bores and adjacent the rear ends of the tubes to accelerate the rate of flow of gases into and through the collector, the mass inertia of the increased rate of the gases flowing from each tube inducing and maintaining the flow of gases into, through and from the tube and super-charging and enhancing the action of the venturi established by the chamber and the outlet bore.

References Cited.

UNITED STATES PATENTS 1,984,242 12/1934 Trainer 60-29 2,841,951 7/1958 Whitcomb 60-32 2,847,819 8/1958 Muller 60-29 FOREIGN PATENTS 363,382 12/1931 Great Britain.

CARLTON R. CROYLE, Primary Examiner DOUGLAS HART, Assistant Examiner

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