Intake and exhaust tuning system

An intake and exhaust tuning system is disclosed. The exhaust system includes a collector slidably mounted within the exhaust fluid path and adjustable by an actuator to change the fluid path length between the collector and the exhaust ports of an engine. The intake tuning system includes a sliding member engaging parallel straight sections of tubes forming the intake system. The position of the sliding member is adjusted to change the length of the intake fluid path. Sealing members suitable for use in the intake and exhaust tuning systems are also disclosed.

FIELD OF THE INVENTION

This invention relates generally to internal combustion engines and, more specifically, to intake and exhaust systems for such engines.

BACKGROUND OF THE INVENTION

Power output and efficiency of internal combustion engines can be improved by tuning the properties of the intake and exhaust systems to take advantage of pressure waves propagating from the engine cylinders. In the exhaust system of a typical engine, exhaust gases are released into the exhaust system from the engine cylinder at high pressure. The resulting pressure wave travels at the speed of sound through the exhaust system. Part of the energy of the pressure wave is reflected back toward the cylinder in the form of a negative pressure wave when the pressure wave passes points where the air channel increases sharply in diameter. This typically occurs at a collector where exhaust pipes from the individual cylinders converge. In the intake system, the sudden intake of air during the intake stroke in four-stroke engines results in a negative wave, a portion of which is reflected toward the cylinder as a pressure wave by openings or dilations in the intake system.

If the return waves arrive at the cylinder at the appropriate time, they aid in the flow of gases in and out of the cylinder. If the exhaust system return wave arrives while the exhaust valve is still open, the negative pressure will help draw exhaust gases out of the cylinder. If the return wave strikes the exhaust port when both the exhaust valve and intake valve are open, the negative pressure aids in drawing a fresh charge of air and fuel into the cylinder. The return wave in the intake system aids in forcing the charge of air and fuel into the cylinder.

The return waves in the intake and exhaust system must be timed correctly in order to arrive at the intake and exhaust ports, respectively, at the appropriate times. In most engines, the air columns in the intake and exhaust systems are fixed. Since the speed of the return waves is substantially constant, the timing of the return waves is also constant. The engine therefore benefits from the return waves only for a small range of operating speeds where the opening of the exhaust and intake ports coincides with the return waves.

Some systems allow for manual adjustment of the length of the air column in the exhaust system in order to adjust engine operating speeds benefiting from the return wave. However, none of the prior systems provides a suitable means for accommodating the full range of operating speeds of the engine.

Accordingly, it would be an advancement in the art to provide a system and method for adapting the acoustic properties of an intake and exhaust systems according to the operating speed of the engine.

SUMMARY OF THE INVENTION

The present invention provides a system for tuning an intake and an exhaust system of an engine. The exhaust tuning system includes a plurality of upstream pipes connected to the exhaust ports of an engine and a downstream pipe. In one example of the invention, the upstream pipes and downstream pipe adjustably connect to a collector to create a fluid path. An actuator couples to the collector to adjust the collector position and vary the fluid path length from the exhaust ports to the collector. An engine control unit (ECU) is coupled to an engine speed sensor and adjusts the collector position in response to changes in the operating speed of the engine.

The collector may include a plurality of inlet tubes overlapping with the upstream tubes. An outlet tube secures to the collector and overlaps with the downstream tube. Sealing members maintain a sliding seal between the inlet tubes and the upstream tubes and between the outlet tube and the downstream tube. The sealing members engaging the inlet tubes may be offset from one another along a longitudinal direction corresponding to a direction of fluid flow within the inlet tubes.

An intake tuning system includes an upstream tube and a downstream tube. The downstream tube connects to the intake ports of an engine. A sliding tube slidably connects to the upstream tube and downstream tube. The upstream tube and downstream tube each include a straight portion oriented parallel to one another. The sliding tube is a U-shaped member and slides along the straight portions. An actuator engages the sliding tube to adjust its position relative to the upstream tube and downstream tube in order to vary the length of the fluid path followed by gases within the intake system. A speed sensor detects the operating speed of the engine provides the output to the ECU. The ECU causes the actuator to adjust the position of the sliding tube in response to sensed changes in the operating speed of the engine.

A sealing member suitable for use in the intake and exhaust system includes a first outer tube section having a first flange extending circumferentially outwardly therefrom and a second outer tube having a second flange extending circumferentially outward therefrom. An inner tube is slidably positioned within the first and second outer tubes sections having the first and second flanges facing one another. A fastener secures the first and second flanges together to capture a compressible seal between the flanges and the inner tube. In one embodiment, the fastener is embodied as first and second rings secured to one another having the first and second flanges positioned therebetween.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1, an exhaust tuning system10includes a plurality of upstream pipes12extending from the exhaust ports of an engine14. A downstream pipe16is distanced from the upstream pipes12and conducts exhaust gasses to exhaust handling systems such as a catalytic converter and the muffler. A collector18extends between the plurality of upstream pipes12and the downstream pipe16to complete the fluid channel therebetween. The collector18slidably connects to the upstream pipes12and the downstream pipe16to adjust the distance between the exhaust port and the point at which the fluid channels from the individual exhaust ports converge. Seals20secure between the upstream pipes12and collector18and provide a sliding seal therebetween. A seal22secures between the downstream pipe16and the collector18.

An actuator24engages the collector18to change the location of the collector18relative to the exhaust ports. A controller26may be electrically coupled to the actuator24to cause the actuator24to move to a desired position. The controller26may translate directives regarding a desired location of the collector18into a quantity of electrical, hydraulic, pneumatic, or other power supplied to the actuator24. The actuator24may provide feedback to the controller regarding the current location of the collector18to enable the controller26to meter power supplied to the actuator24to achieve an intended change in position.

The collector18includes a plurality of inlet tubes28overlapping with the upstream pipes12. The upstream pipes12may include a straight portion30formed thereon or secured thereto for engaging the inlet tubes28. The inlet tubes28are positioned either inside or outside the upstream pipes12. The sealing members20typically secure to the outermost of the inlet tubes28and upstream pipes12. An outlet tube32overlaps with the downstream pipe16and is positioned either in- or outside of the downstream pipe16. The sealing member22secures to the outermost of the outlet tube32and downstream pipe16.

A converging section34, or funnel, couples the inlet tubes28to the outlet tube32. The converging section34provides a dilation point within the air column thereby serving to reflect negative pressure waves toward the exhaust ports of the engine. Pressure waves propagating through the upstream pipes12will expand into adjacent upstream pipes12and the downstream pipe16upon reaching the converging section34. This sudden dilation of the fluid path at the converging section34results in a negative pressure wave propagating back up the upstream pipe12that originated the pressure wave. The arrangement of the upstream pipes12, inlet tubes28, and converging section34provide a narrow fluid path up to the dilation point at the converging section34.

The above described arrangement of upstream pipes12, inlet tubes28, and the converging section34ensures that the pressure waves from the different cylinders of the engine travel separate fluid paths up to the dilation point at the converging section34. This avoids dissipation of the pressure wave and negative pressure wave. It further avoids interference between cylinders, enabling more predictable behavior and more precise tuning of the exhaust tuning system10.

The converging section34may include an ear36, or bracket, extending therefrom to engage the actuator24. In one embodiment, the actuator24is embodied as a ball-screw, hydraulic, or pneumatic, cylinder38and piston40. In the illustrated embodiment, the piston40secures to the ear36and the cylinder38secures to the downstream pipe16by means of a bracket42. Alternatively, the cylinder38or piston40may secure to one or more of the upstream pipes12.

Referring toFIG. 2, while still referring toFIG. 1, the converging section34may include a front plate44secured at the larger end thereof. The front plate44has a plurality of inlet apertures46receiving the inlet tubes28. An outlet aperture48is formed at the narrow end of the converging section and receives the outlet tube32. The inlet apertures46may be symmetrically positioned on the front plate44to provide consistent wave propagation properties for all fluid paths.

Referring toFIG. 3, in one embodiment, the sealing members20may be longitudinally offset from one another to accommodate larger sealing structures. In the illustrated embodiment, the sealing members20secure to inlet tubes28having differing lengths. Each inlet tube28may have a unique length or have a length that is different from immediately adjacent tubes28. In an alternative embodiment, the inlet tubes28have substantially equal lengths. In such embodiments, the upstream pipes12may have either equal or differing lengths and secure to the sealing members20such that the upstream pipes12extend outside the inlet tubes28.

Various embodiments of the actuator24are also possible. For example, the actuator24may drive a threaded rod54engaging a threaded aperture56formed in the converging section34or formed in an ear58secured to the converging section. The actuator24may secure to any fixed structure forming the engine or automobile in which the exhaust system is used. The actuator24may also secure to the downstream pipe16, as illustrated, or to the upstream pipes12. In the embodiment ofFIG. 3, the actuator may be embodied as a stepper motor60or servo60. A controller26may adjust the location of the collector18by causing the stepper motor60to rotate the rod54a specific number of degrees causing the threaded aperture56to translate along the rod54.

Referring toFIG. 4, an exhaust tuning system10includes an engine control unit70. The engine control unit70receives inputs from sensor such as an operating speed sensor72, temperature sensor74, pressure sensor76, and the like. The ECU70provides an output to the actuator24, or the controller26of the actuator24. The ECU70may also receive feed back from the actuator24regarding the current position of the collector18.

The ECU70determines, based on the inputs received, a collector position suitable for coordinating pressure waves within the exhaust system with opening and closing of the exhaust ports. The ECU70may monitor the inputs and make substantially constant or regularly periodic adjustments to collector position. Alternatively, the ECU70may adjust the collector position only upon detection of a change in one or more of the inputs exceeding a specific threshold. The threshold may be proportional or otherwise related to operating speed or another parameter. The ECU70may map collector positions to specific values, or combinations of values, of one or more parameters such as operating speed, exhaust temperature, exhaust pressure and the like. In one embodiment, only operating speed is used. In other embodiments, changes in the speed of the waves due to temperature and pressure changes may be accommodated by mapping collector positions to values for operating speed, temperature, and/or pressure. Some engines may vary the timing of valve opening and closing relative to crankshaft position according to operating speed, load on the engine, and other parameters. Accordingly, the ECU70may adjust the collector position to coincide with these variations.

Mapping may be accomplished by various means. In one embodiment, tables map values, or ranges of values, of inputs to the ECU70to collector positions. In other embodiments, the ECU70accomplishes mapping according to a mathematical formula. In still other embodiments, the ECU70accomplishes mapping according to a plurality of mathematical formulae each corresponding to a range of input values for one or more inputs. Mathematical formulae and maps are typically generated by testing of a particular engine to determine which collector position provide the highest performance gains for a particular operating speed.

A formula for calculating collector position is L=((850*(360−EVO))/RPM)−3. Where L is the length of the fluid path from the engine14to the collector18, EVO (exhaust valve opening) is the angular position at which the exhaust valve opens, and RPM (revolutions per minute) is the angular velocity of the crankshaft. A collector position achieving the desired length L may then be calculated.

In some embodiments, calculated values for L may be adjusted based on tracking of the exhaust gas pressure at the exhaust port. For example, where tracking of exhaust pressure shows that a return wave is arriving early or late, the ECU70may adjust the collector position to lengthen or shorten, respectively, the length L. In still other embodiments, feedback of exhaust gas pressure is the only means used to determine collector position. The ECU70, for example, may determine whether the return wave is arriving early or late and adjust the collector position to lengthen or shorten, respectively, the length of the fluid path from the engine14to the collector. The ECU70may sample the arrival time of the return waves and adjust collector position substantially continuously or periodically in order to cause the collector position to track changes in engine operating speed.

Referring toFIG. 5, in an alternative embodiment, the operating speed of the engine is measured by a digital tachometer80coupled to the distributor82of the engine. The output of the digital tachometer is input to the ECU70. The ECU70calculates a desired fluid path length or collector position as described above. The ECU70may provide an output to a control module84coupled to an indexer driver86driving the actuator24. The control module84refines the output of the ECU70to produce an output signal to the indexer driver86. The control module84translates a position, change in position, or fluid path length from the ECU70into signals provided to the indexer driver86effective to achieve the desired change in position.

Referring toFIG. 6, a method90for tuning an engine exhaust system may include detecting92the current operating speed of the engine. The exhaust gas temperature may also be optionally detected94. The exhaust gas pressure may also be optionally detected96. A fluid path length providing proper return wave timing is then calculated98, based on the operating speed detected in step92and optionally based on the exhaust gas temperature and exhaust gas pressure detected in steps94and96. Calculation98may include applying an equation to operating conditions or consulting a map containing a mathematically or experimentally determined fluid path length or slider position providing desired performance at a given operating condition, such as RPM. The collector position corresponding to the length calculated in step92is then calculated100and the position of the collector18adjusted102to the calculated position.

The method90may optionally include detecting104arrival of the return wave, and recalculating106the collector position if the return wave arrives early or late. The collector position is then readjusted108. The steps104,106, and108may be repeated multiple times for a single iteration of the method90.

Referring toFIG. 7, an intake tuning system120includes a throttle122controlling flow of air into a throttle tube124. A sliding member126engages the throttle tube124and an intake tube128to create a fluid path from the throttle122to the intake port of the engine14. In the illustrated embodiment, the sliding member is U-shaped. The U-shaped configuration enables translation of the sliding member126to change the length of the fluid path between the throttle122and the intake port. The U-shaped configuration further causes displacement of the sliding member to result in a change in the fluid path length equal to twice the amount of the displacement. A sealing member132creates a sliding seal between the throttle tube124and the sliding member126. A sealing member134creates a sliding seal between the sliding member126and the intake tube128.

An actuator136engages the sliding member126to adjust the length of the fluid path between the throttle122and the engine14. A controller138may be coupled to the actuator and meter power supplied to the actuator136to achieve a desired change in position of the sliding member126. In the illustrated embodiment, the actuator136is a ball-screw, hydraulic, or pneumatic cylinder140and piston142coupled to the sliding member126to cause translation thereof. A first end146of the cylinder140and piston142combination may engage the sliding member126by means of a cross member144extending between the legs of the U-shaped sliding member126. Alternatively, the first end146secures directly to the sliding member126.

A second end148of the cylinder140and piston142combination secures to the engine14, such as to the head or block of the engine. In the illustrated embodiment, the second end148secures to the head of the engine14between the throttle tube124and intake tube128. The second end148may secure to a bracket150secured to the head of the engine14proximate a valve cover152. The throttle122or the throttle tube124may likewise secure to a bracket154secured to the head of the engine14.

Referring toFIGS. 8 and 9, an engine may include multiple throttle tubes124, sliding members126, and intake tubes128coupled to the engine's multiple intake ports. In such embodiments, a cross member146may be embodied as a plate156having multiple apertures158formed therein for receiving the arms of the U-shaped sliding members126.

The sliding member126may engage a guide158to ensure smooth changes in sliding member position. In the illustrated embodiment, the guide158is two grooved rails160extending parallel to the intake tubes128. Struts164supporting the rails160secure to the block of the engine14, or other structure within an engine compartment. In the illustrated embodiment, the struts164extend from a free end166of the rails160to the engine14. The struts164may be arranged in the crossed configuration ofFIG. 8having a gusset166securing the struts164to one another near the intersection point. The rails160engage keys168secured to the sliding member126or cross member144. In some embodiments, the guide158secures to the sliding member126whereas the keys162are fixed relative to the engine14.

Referring toFIG. 10, in some embodiments, an intermediate pipe174slidably engages the sliding member126and the throttle tube124. The intermediate pipe174enables a broader range of fluid path lengths inasmuch as the intermediate pipe174slides within either the sliding member126or the throttle tube124for shorter fluid path lengths. A second sealing member176slidably seals the intermediate member with respect to the throttle tube124.

Referring toFIG. 11, an intake tuning system120includes an engine control unit70. The engine control unit70receives inputs from sensor such as an operating speed sensor72, temperature sensor74, pressure sensor76, and the like. The ECU70provides an output to the actuator136or the controller128of the actuator136. The ECU70may also receive feed back from the actuator136regarding the current position of the collector sliding member126.

The ECU70determines, based on the inputs received, a sliding member position suitable for coordinating pressure waves within the intake tuning system120with opening and closing of the intake ports. The ECU70may monitor the inputs and make substantially constant or regularly periodic adjustments to sliding member position. Alternatively, the ECU70may adjust the sliding member position only upon detection of a change in one or more of the inputs exceeding a specific threshold. The threshold may be proportional or otherwise related to operating speed or another parameter. The ECU70may map sliding member positions to specific values, or combinations of values, of one or more parameters such as operating speed, exhaust temperature, intake pressure and the like. In one embodiment, only operating speed is used. In other embodiments, changes in the speed of the waves due to temperature and pressure changes may be accommodated by mapping collector positions to values for operating speed, temperature, and/or pressure. Some engines may vary the timing of valve opening and closing relative to crankshaft position according to operating speed, load on the engine, and other parameters. Accordingly, the ECU70may adjust the sliding member position to coincide with these variations.

Mapping may be accomplished by various means. In one embodiment, tables map values, or ranges of values, of inputs to the ECU70to sliding member positions. In other embodiments, the ECU70accomplishes mapping according to a mathematical formula. In still other embodiments, the ECU70accomplishes mapping according to a plurality of mathematical formulae each corresponding to a range of input values for one or more inputs. Mathematical formulae and maps are typically generated by testing of a particular engine to determine which sliding member position provide the highest performance gains for a particular operating speed. In some instances, particular combinations of sliding member position and collector position provide better performance for a particular operating speed than others. Accordingly, testing to determine mathematical formulae and maps may include identifying such combinations and developing maps and formulae to achieve them during engine operation.

In some embodiments, calculated values for sliding member position may be adjusted based on tracking of the intake gas pressure at the intake port. For example, where tracking of intake pressure shows that a return wave is arriving early or late, the ECU70may adjust the sliding member position to lengthen or shorten, respectively, fluid path length. In still other embodiments, feedback of intake pressure is the only means used to determine sliding member position. The ECU70, for example, may determine whether the return wave is arriving early or late and adjust the sliding member position to lengthen or shorten, respectively, the length of the fluid path from the engine14to the throttle122. The ECU70may sample the arrival time of the return waves and adjust sliding member position substantially continuously or periodically in order to cause the sliding member position to track changes in engine operating speed.

Referring toFIG. 12, in one embodiment, the operating speed of the engine is measured by a digital tachometer80coupled to the distributor82of the engine. The output of the digital tachometer80is input to the ECU70. The ECU70calculates a desired fluid path length or sliding member position as described above. The ECU70may provide an output to a control module128coupled to an indexer driver190driving the actuator136. The control module128refines the output of the ECU70to produce an output signal to the indexer driver190. The control module128translates a position, change in position, or fluid path length from the ECU70into signals provided to the indexer driver190effective to achieve the desired change in position.

Referring toFIG. 13, a method200for tuning an engine exhaust system may include detecting202the current operating speed of the engine. The intake temperature may also be optionally detected204. The intake pressure may also be optionally detected206. A fluid path length providing proper return wave timing is then calculated208, based on the operating speed detected in step202and optionally based on the intake temperature and intake pressure detected in steps204and206. The sliding member position corresponding to the length calculated in step202is then calculated210and the position of the collector18adjusted212to the calculated position.

The method200may optionally include detecting214arrival of the return wave, and recalculating216the sliding member position if the return wave arrives early or late. The sliding member position is then readjusted218. The steps214,216, and218may be repeated multiple times for a single iteration of the method200.

The exhaust tuning system10and intake tuning system120and associated methods may be used to achieve a variety of objectives by controlling the timing of returning positive and negative waves. For example, the timing may be controlled to prevent reversion, in which exhaust gasses escape into the atmosphere through the intake or exhaust runners.

Timing may also be controlled to help the cylinder to achieve a higher percentage of volumetric efficiency by drawing in air during the valve overlap period, and then forcing an additional volume of air (or air-fuel mixture for carbureted engines) into the cylinder at the end of the intake cycle. In the intake-exhaust cycles, beginning with exhaust valve open (EVO), a positive pressure wave is generated when the exhaust valve opens and bow-down is in progress. If the length of the exhaust runner is correct for the RPM, then that wave will return to the cylinder as a negative pressure wave from the open end of the exhaust runner during the intake-exhaust valve overlap period to prevent reversion, draw off residual exhaust gas, and start the inflow of air by means of lowered cylinder pressure.

After the overlap period, the action of the piston moving down the cylinder and drawing in a fresh charge generates a strong suction wave. This wave is then reflected off the open end of the intake runner as a compression wave. If the intake runner is tuned to the proper length for a given RPM, the returning compression wave will force an additional charge of air into the cylinder just before the intake valve closes. This increases cylinder pressure and volumetric efficiency, and therefore torque. At the same time, reversion through the intake system is prevented by maintaining positive pressure at the intake port until the exhaust valve closes. The wave generated at intake valve close (IVC) will echo several times and will have become weaker by the time intake valve open (IVO) occurs. However, it appears to nonetheless provide a significant improvement.

The above benefits obtained by the tuning systems10,120have particularly beneficial application in the field of lean-burn technology, in which emissions are reduced by using an extremely lean fuel/air mixture. This approach reduces the formation of Nitrous Oxides by reducing the temperature of combustion. Increasing cylinder pressure at IVC serves to increase the amount of fuel that can be added while still maintaining a high air/fuel ratio.

An engine may be dynamically tuned using one or both of the exhaust tuning system10and intake tuning system120to achieve all or part of these benefits. In addition to the methods described above, dynamic tuning may be accomplished by consulting an empirically derived map or curve fit of tuning system configurations and engine operating conditions. For example, incremental positions of a slider126and collector18may be mapped to one or more RPMs. In operation, a controller consults the map and sets the slider126and collector position to the position mapped to the present operating speed of the engine. Mappings may map tuning systems10,120positions to multiple variables in addition to RPM such as throttle position, engine temperature, throttle position, and the like. Maps may be derived by connecting an engine or vehicle to a dynamometer and experimenting with tuning systems10,120positions to determine which provides a preferred performance characteristic such as fuel efficiency, torque, horsepower, or the like.

The sealing members20,22,132,134, and176may be embodied as illustrated inFIG. 14. A flange230is formed on an outer tube232. A second flange234is formed on an extension236. The flanges230,234capture an o-ring238encircling an inner tube240. The outer tube232and inner tube240may be any tube forming part of the exhaust tuning system10or intake tuning system120, such as the upstream tubes12, downstream tube16, inlet tubes28, outlet tube32, throttle tube134, sliding member136, intake tube128, or intermediate tube174.

A retainer242maintains the flanges230,234over the o-ring238. The retainer242may force the flanges230,234together to the extent that the o-ring238is pressed against the inner tube240. In one embodiment, the retainer242is embodied as rings244a,244babutting the flanges230,234, respectively. Fasteners, such as bolts246and nuts248may force the rings244a,244btogether. In some embodiments, spacers250maintain a minimum separation between the rings244a,244b. The inner tube240may have a spacer252at an end thereof positioned within the outer tube232. The spacer252may serve to reduce movement of the inner tube240within the outer tube232despite the difference in the diameters thereof and prevent complete removal of the inner tube240from the outer tube232. The spacer252may also provide a partial seal between the outer tube232and the inner tube240.

A felt ring254may be positioned between the extension236and the inner tube240. The felt ring254serves to reduce the amount of contaminants reaching the o-ring238. The felt ring254may also carry lubricant, which is deposited on the inner tube240. An aperture256, or zert, may be provided adjacent the felt ring254to facilitate application of lubricant thereto. Internal lands258formed in the extension236retain the felt ring254.

Referring toFIGS. 15 and 16, the sealing members20,22,132,134, and176may include a bearing seal260in addition to a seal, such as the polymer o-ring238. The bearing seal260may include a plurality of races262receiving roller bearings264. The bearing surfaces of the roller bearings264have a concave portion having a radius substantially matching that of the inner tube240. The races262have a convex bearing surface substantially conforming to that of the bearings264. In the embodiment ofFIGS. 15 and 16, the o-ring238is positioned within a groove266formed in the outer tube232.

The embodiment ofFIGS. 15 and 16may be formed as separable sections268a,268bsecurable to one another by fasteners270engaging flanges272formed on the sections268a,2686b. Set screws274, or like fastening means, secure sections268a,268bto the outer tube232or inner tube240. In some embodiments, the cross member144is secured by a fastener270to the sections268a,268b.

Referring toFIG. 17, in an alternative embodiment, the sealing members20,22,132,134, and176include rigid rings296,298seated within a groove300formed in the outer tube232or a member secured to the outer tube232. One of the rings296,298has an undeformed inner diameter slightly smaller than the inner tube240such that the ring296,298elastically retains itself around the tube240to create a seal. The other of the rings296,298has an undeformed outer diameter slightly larger than the inside diameter of the groove300such that it elastically retains itself within the groove300to create a seal.

In some embodiments, an additional set of rings302,304is provided within a groove306. In one embodiment, rings296and304have an undeformed outer diameter slightly larger than their respective grooves300,306, whereas rings198,302have undeformed inner diameters slightly smaller than the outer diameter of the inner tube240. In this manner, as the inner tube240slides within the outer tube232, at least one set of rings will be forced against one another to enhance sealing.

The rings296,298may each have a gap308formed therein. The gap308facilitates deformation of the rings296,298,302,304when positioning them into their respective grooves300,306and around the inner tube240. The gaps308of the rings296,298,302,304are offset from one another to hinder leakage of gases therethrough. An aperture310may extend through the outer tube232to facilitate injection of lubricant over the rings296,298. A set screw312is threaded into the aperture310during operation to seal the aperture310.

Referring toFIG. 19, in an alternative embodiment of the sealing member ofFIG. 18, lubrication for one or more of the sealing members20,22,132,134, and176is provided by a felt ring256positioned within an outer ring314. An inner ring316secures to the outer ring314, effectively capturing the felt ring256between the inner ring316and the extension236. An aperture318is formed in the outer ring314to permit the injection of oil onto the felt ring. An oil cup320may secure to the outer ring314over the aperture318and bear a cap322. The cap322may be opened to permit filling of the oil cup320and then closed to ensure a reservoir of oil is available to soak the felt ring254. In some embodiments, the outer ring314, inner ring316, and extension236are secured to one another such as by tack welding, bonding, rivets, or the like. In the embodiment ofFIG. 19, the end324of the inner tube240has an outwardly tapered inner surface to improve fluid flow. The inner tube240has an outer diameter such that it is slidable within the outer tube232and extension236. The extension236and outer tube232are secured to one another in a similar manner to the embodiment ofFIG. 19, such as by rings244a,244babutting the flanges230,234, respectively. Fasteners, such as bolts246and nuts248may force the rings244a,244btogether.

Referring toFIGS. 20-22, in an alternative embodiment, the intake tuning system70includes one or more dampers326. The dampers326may serve to maintain the plate156square relative to the throttle tube124, sliding members126, and intake tubes128. The force of the vacuum exerted on the sliding members126may tend to cause the sliding members126to skew. The steadying force exerted by the dampers326helps to counteract this tendency. In the illustrated embodiment, four dampers326are used proximate the four corners of the plate156vertically between the legs of the sliding members126and located laterally on either side of the sliding members126.

In the illustrated embodiment, the dampers326are embodied as pistons328and cylinders330. The cylinders330may be spring loaded such that the pistons328are biased outwardly. Alternatively, the cylinders330may contain hydraulic fluid, or other means, exerting frictional force on the pistons328such that movement is resisted. In yet another alternative, the cylinders330both bias the pistons328outwardly and exert frictional force.

In the embodiment ofFIGS. 20-22, the plate156secures to the sliding members126proximate the sealing members132. The plate156may secure directly to the sliding members126or the sealing members132,134. The sliding members126or the sealing members132secure to the plate156by means of welds, bolts, or like fastening means. For sealing members132,134embodied as illustrated inFIGS. 14 and 19, the plate156may secure to the outer ring314, extension236, or rings244a,244b.

The cylinder140and piston142, in the illustrated embodiment, are positioned between the throttle tubes124. The intake manifold332securing to the throttle tubes124may have a gap334formed thereon suitable for receiving the cylinder140. A mounting bracket336may likewise be positioned within the gap334. The cylinder140may mount to the manifold332.