Where a manifold usually has several holes converging into a common chamber to route all your gasses, a header has precisely formed tubes that curve gently to join your exhaust ports to your exhaust pipe. How does this help? First of all, as with any fluid, exhaust gasses must be treated gently for maximum horsepower production.
You don't want to just slam-bang exhaust gas from your engine into the exhaust system. No way, Jo-se'! Just as the body of your '94 Eclipse is beautiful, swoopy, and aerodynamic, so must be the inside of your exhaust system. Secondly, a header can be "tuned" to slightly alter your engines' characteristics.
We'll go in-depth into header tuning a little later. Nextly, exhaust gasses exit from your manifold or header, travel through a bit of pipe, then end up in the catalytic converter, or "cat".
The cat's main job is to help clean up some of the harmful chemicals from your exhaust gas so they don't end up in your lungs. In most cars, they also do a great job of quieting things down and giving any exhaust system a deeper, mellow tone. There's room for debate on this, but in our experience, removing a catalytic converter from a new car won't gain you much in the horsepower department.
Are you a muff? Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be. For the same reason gunshots are loud, engine exhaust is loud. Not 5. Even the gentleman's gentleman has gotta use a muffler, or system of mufflers, on their exhaust.
A muffler can no more "make" horsepower than Wile E. Coyote can catch roadrunners. Any technician with any dyno experience will tell you that the best mufflers are no mufflers at all! Types of Muff Mufflers can take care of the silencing chores by three major methods: Absorption, Restriction, and Reflection. Mufflers can use one method, or all three, to attenuate sound that is not so pleasing to the ears of the Highway Patrol.
The absorption method is probably the least effective at quelling engine roar, but the benefit is that "absorbers" are also best at letting exhaust gas through. Absorption mufflers are also the simplest. All of the above named mufflers utilize a simple construction consisting of a perforated tube that goes through a can filled with a packing material, such as fiberglass or steel wool. This is similar to simply punching holes in your exhaust pipe, then wrapping it up with insulation.
Neat, huh? Another trick absorption mufflers use to kill off noise is, well, tricky. For example, the Hooker Aero Chamber muffler is a straight-through design, with a catch.
Instead of a simple, perforated tube, there is a chamber inside the muffler that is much larger than the rest of the exhaust pipe. This design abates sound more efficiently than your standard straight-through because when the exhaust gasses enter this large chamber they slow down dramatically. This gives them more time to dwell in the sound insulation, and thus absorb more noise. The large chamber gently tapers back into the smaller size of your exhaust pipe, and the exhaust gasses are sent on their merry way to the tailpipe.
Restriction Doesn't that word just make your skin crawl? It's right up there in the same league with words like "maim" and "rape". Obviously, a restrictive muffler doesn't require much engineering expertise, and is almost always the least expensive to manufacture.
Thus, we find restrictive mufflers on almost all OEM exhaust systems. We won't waste much time on the restrictive muffler except to say that if you got 'em, you might not want to flaunt 'em. Reflection Probably the most sophisticated type of muffler is the reflector. They often utilize absorption principles in conjunction with reflection to make the ultimate high-performance silencer.
Remember any of your junior high school math? Specifically, that like numbers cancel each other when on a criss-cross? That's the same principal used by the reflective muffler. Sound is a wave. And when two like waves collide, they will "cancel" each other and leave nothing to call a corpse but a spot of low-grade heat. There are numerous engineering tricks used in the reflective muffler. Hedman Hedders makes a muffler that looks a lot like a glasspack.
In fact, it is a glasspack with a catch. And, this muffler is packed with a lot of fiberglass to help absorb any straggling noise that might be lagging behind. The Exhaust Pulse To gain a more complete understanding of how mufflers and headers do their job, we must be familiar with the dynamics of the exhaust pulse itself.
Exhaust gas does not come out of the engine in one continuous stream. Since exhaust valves open and close, exhaust gas will flow, then stop, and then flow again as the exhaust valve opens. The more cylinders you have, the closer together these pulses run. Keep in mind that for a "pulse" to move, the leading edge must be of a higher pressure than the surrounding atmosphere. The "body" of a pulse is very close to ambient pressure, and the tail end of the pulse is lower than ambient.
It is so low, in fact, that it is almost a complete vacuum! The pressure differential is what keeps a pulse moving. A good Mr. Wizard experiment to illustrate this is a coffee can with the metal ends cut out and replaced with the plastic lids.
Cut a hole in one of the lids, point it toward a lit candle and thump on the other plastic lid. What happens? The candle flame jumps, then blows out! The "jump" is caused by the high-pressure bow of the pulse we just created, and the candle goes out because the trailing portion of the pulse doesn't have enough oxygen-containing air to support combustion.
Ok, now that we know that exhaust gas is actually a series of pulses, we can use this knowledge to propagate the forward-motion to the tailpipe. On the other. Yet, the number of passages 30 in a given cross sectional area of the present substrate 28 closely approaches that of the passages P in a conventional converter substrate S, due to the relatively thin substrate walls 32 of the present converter substrate Due to their relatively high surface area per pass and volume ratio, the thin substrate walls 32 serve to absorb heat more quickly than the relatively thick walls W of prior art substrates S.
This allows the present catalytic converter element 24 to reach its normal operating temperature more quickly than catalytic converters of the prior art, thus reducing the "cold start" period when emissions are relatively high due to the need for exhaust gases to warm up the converter to reach an optimum temperature for the catalytic reactions to occur efficiently.
Thus, the catalytic converter 24 of the present catalytic converter and resonator combination 10 reduces the period of time following a cold start when exhaust emissions are relatively high due to the catalytic converter being relatively cool.
While conventional converter substrates S have been formed of relatively expensive metals in order to provide the required structural strength at the elevated temperatures found in such devices, the catalytic converter 24 of the present catalytic converter and resonator combination 10 preferably uses a ceramic material for the substrate walls Such ceramic materials provide excellent resistance to heat, but a relatively strong material is required in order to provide the required structural strength, particularly in the case of the relatively thin substrate walls 32 of the present invention.
A ceramic material known as Dow-Corning XT tm , manufactured by the Dow-Corning Company, has been found to be suitable for the construction of such thin wall catalytic converter substrates 28 of the present invention.
Other materials providing sufficient structural strength at the elevated temperatures experienced within an operating catalytic converter, may be used as desired.
The canister rearward portion 18 includes a resonator element 34 installed therein. The resonator element 34 is a generally tubular or cylindrical device, which may be rolled from a flat sheet of suitable metal or otherwise formed. The resonator element 34 has a hollow core 36, a forward end 38, an opposite rearward end 40, and an outer diameter 42 which is substantially less than the inner diameter 26 of the rear portion 18 of the canister This difference between the inner diameter 26 of the canister rearward portion 18 and the outer diameter 42 of the resonator element 34, defines a sound attenuating plenum 44 therebetween.
The resonator element 34 includes a plurality of sound attenuating perforations 46 formed radially therethrough, for the attenuation of exhaust sound in a relatively narrow range of frequencies. The passages or perforations 46 may be dimensioned and spaced to accommodate different frequency ranges as desired, as is known in the art. The resonator element 34 is secured concentrically within the canister rearward portion 18 by a forward plate 48 and opposite rearward plate 50, affixed respectively to the forward end 38 and rearward end 40 of the resonator tube 34 and within the rearward portion 18 of the canister 12, normal to the axis of the resonator pipe 34 and canister These two plates 48 and 50 are toroid shaped, to allow exhaust gases to pass from a plenum 52 disposed between the catalytic converter element 24 and the forward end 38 of the resonator tube element 34, through the central passage of the forward plate 48 and thence through the hollow core 36 of the resonator pipe element 34 and out through the central passage of the rearward plate 50, as indicated by the exhaust gas arrows G.
The essentially equal diameters 22 of the catalytic converter element 24 and inner surface of the forward portion 16 of the canister 12 serve to affix the catalytic converter element 24 concentrically within the canister The tight fit of the catalytic converter element 24 within the forward portion 16 of the canister 12, provides a tight seal between the catalytic converter element 24 and forward portion 16 of the canister 12, thereby precluding any bypass flow of exhaust gases therebetween.
The toroidal plates 48 and 50 serve to secure the resonator pipe element 34 concentrically within the rearward portion 18 of the canister 12, with the tight fit of the catalytic converter element 24 within the forward portion 16 of the canister 12 serving to secure the converter element 24 concentrically therein.
Thus, it will be seen that all of the above elements, i. As noted further above, the resonator portion 34 of the present invention functions by attenuating sound of a predetermined frequency. However, depending upon the relative pressures between the resonator core 36 and the resonator plenum 44, some exhaust gases may flow into the plenum Accordingly, the rearward resonator attachment plate 50 may include one or more generally peripheral passages 54 therethrough, for allowing exhaust gases to depart the resonator plenum 44 and exit the canister 12 from the outlet end 20 thereof.
The forward resonator attachment plate 48 may be formed with a solid periphery, to preclude the flow of exhaust gases from the converter and resonator plenum 52, directly into the resonator plenum As noted further above, resonators serve to attenuate sounds in only a relatively narrow band or range of frequencies, depending upon their construction. The range of frequencies damped by a given resonator, is primarily dependent upon the length of the internal resonator element or pipe therein, with shorter elements resulting in the control of relatively higher frequencies, and longer elements being adapted for the reduction of relatively lower frequencies.
As the predominant frequencies emitted by a given internal combustion engine will be dependent upon the configuration of the engine, it will be seen that it is desirable to provide some means for adjusting a resonator configuration for a given installation. Such adjustability may be important even for different resonators to be used with identical engines in identical exhaust systems, but in different vehicles, due to different resonant qualities of the specific vehicle structure.
Accordingly, the present invention provides for adjustment or tuning of the resonator frequency response band, by means of the combination catalytic converter and resonator.
The converter and resonator combination 60 is constructed similarly to the converter and resonator combination 10 of Figure 1, having a hollow, monolithic tubular canister or shell 62 with a forward or inlet end 64, a forward portion 66 immediately behind and adjacent the inlet end 64, and a rearward portion 68 immediately behind and adjacent the forward portion However, the rearward portion 68 terminates in a conical section 70, which has a minor diameter equal to the diameter of the resonator element 72 therein.
The forward portion 66 is essentially identical to the forward portion 16 of the converter and resonator combination device 10 of Figure 1, with the forward portion 66 being dimensioned to hold and secure at least one catalytic converter element 24 therein.
The element 24 of the device 60 of Figure 2 is identical to the element 24 of the device 10 of Figure 1, having a substrate 28 with a plurality of longitudinal passages 30 therethrough defined by walls 32, as shown in detail in Figure 6. The specific structural details and materials of the catalytic converter 24 have been discussed in detail further above in the discussion of the converter and resonator combination 10 embodiment of Figure 1, and need not be repeated here.
The canister rearward portion 68 includes a resonator element 72 installed therein, constructed generally in the same manner as that described for the resonator element 34 of the embodiment 10 of Figure 1. The resonator element 72 of the embodiment 68 of Figure 2 has a hollow core 74, a forward end 76, and an opposite rearward end 78, which also comprises the rear or outlet pipe for the converter and resonator combination embodiment 60 of Figure 2.
The forward portion of the resonator element 72 is formed essentially identically to the resonator element 34 of the device 10 of Figure 1, having a plurality of relatively small sound attenuating perforations or passages 80 formed through the wall thereof. The forward end 76 of the resonator 72 is secured concentrically within the canister rearward portion 68 by a forward plate It will be seen that the rear portion of the embodiment 60 of Figure 2 differs from that of the embodiment 10 of Figure 1, in that there is no need for a rearward resonator element support plate in the embodiment 60 of Figure 2.
As the resonator element 72 extends rearwardly from the rear conical portion 70 of the shell 62, the rear portion 78 of the element 72 is supported by the smaller diameter, necked down end portion 84 of the conical portion 70, and is welded at that joint to provide a leakproof seal at the time of manufacture or assembly.
Accordingly, the rearward portion 78 of the resonator tube 72 is devoid of perforations, in order to provide a leakproof outlet for exhaust gases passing through the device 60 and onward to a trailing exhaust pipe not shown conventionally connected to the outlet end 78 of the resonator pipe element The remainder of the catalytic converter and resonator combination 60 of Figure 2 is constructed similarly to the embodiment 10 of Figure 1, with the resonator element 72 having an outer diameter substantially less than the inner diameter of the rear portion 68 of the canister This difference between the inner diameter of the canister rearward portion 68 and the outer diameter of the resonator element 72, defines a sound attenuating plenum 86 therebetween.
A forward sound attenuating plenum 88 is also defined between the rear of the catalytic converter element 24 and the forward end 76 of the resonator element 72 and its supporting front plate 82, within the outer shell 62 of the combination catalytic converter and resonator device The toroidal front plate 82, along with the necked down rearward end 84 of the conical rearward portion 70 of the shell 62, serve to secure the resonator pipe element 72 concentrically within the rearward portion 68 of the canister 62, with the tight fit of the catalytic converter element 24 within the forward portion 66 of the canister 62 serving to secure the converter element 24 concentrically therein.
Engine exhaust gases flow through the device 60 of. Figure 2 generally in the manner described for the exhaust gas flow through the converter and resonator 10 of Figure 1, as indicated by the exhaust gas arrows G. While the small perforations 80 are adapted to attenuate sounds of a certain predetermined frequency range, it will be seen that some exhaust gases G will flow through these passages However, this is of no consequence, because as gas pressure equalizes within the plenum 86 between the resonator element 72 and the outer shell 62, those gases will flow back through the resonator perforations 80 to be entrained in the exhaust gas flow G as it passes through the resonator element The above described construction for the combination catalytic converter and resonator combination 60 of Figure 2, provides a means of adjusting the length of the resonator element 72 within the outer shell 62 of the device 60 during manufacture or assembly.
The resonator forward end support plate 82 may be welded or otherwise suitably secured to the forward end 76 of the resonator element 72, and the assembly inserted into the outer shell 62 of the device 60 before the conical rearward end 70 is welded to the rearward end 68 of the outer shell or canister At this point, the rearward conical end 70 is welded in place, with the rearward or outlet portion or end 78 of the resonator tube element 72 extending outwardly past the smaller diameter trailing end 84 of the rearward element 70 of the shell or canister It will be seen that at this point, the resonator element 72 and its attached forward end support plate 82 may be adjusted or repositioned as desired axially within the outer shell or canister 62, as indicated by the adjustment arrow A in Figure 2.
This allows the resonator element 72 to be positionally adjusted to a predetermined position as desired, in order to achieve the attenuation of sound within a certain predetermined frequency range. Extending the resonator element 72 rearwardly from the rearward portion 70 of the device 60 with less of the element 72 residing within the plenum 86 results in the attenuation of relatively higher frequencies, while inserting the resonator element 72 into the interior of the shell 62 results in the attenuation of relatively lower frequencies.
The seam or joint defined by the smaller diameter rearward end 84 of the conical rearward end 70 of the outer shell or canister 62 and the unperforated end portion 78 of the resonator element 72, is then welded to provide a leakproof seal and to immovably affix the resonator element 72 in place. Thus, the catalytic converter and resonator combination device 60 of Figure 2, may be adjustably.
While the above described adjustment of the resonator element 72 within the shell or canister 62 affects the attenuated frequency range of the device 60 to a great extent, it has very little, if any, effect on the volume of sound which emanates from the device As there is no structure within the toroidal plenum 86 surrounding the resonator element 72 , there may be a certain amount of sound which radiates from the resonator element 72, through the plenum 86, and outwardly through the walls of the outer shell or canister Accordingly, the plenum volume 86 may be filled, at least to a certain degree as desired, with a sound absorbing material 90, in order to dampen the volume of sound which may emanate from the device Such material may comprise glass fiber, corrosion resistant metal strands "stainless steel wool" , spun fibers or strands of a rock or stone material such as basalt "rock wool" , or other suitable material which is capable of retaining its structure when subjected to the high temperatures occurring within the present device The above described embodiments each include a single resonator tube element 34 or 72 with a single catalytic converter element 24 concentric therewith.
However, it will be seen that additional catalytic converter elements may be added in series with the single element 24 of the devices 10 and 60 respectively of Figures 1 and 2, if so desired, for further efficiency. Figure 3 discloses such an alternate embodiment, designated as catalytic converter and resonator combination The catalytic converter and resonator is constructed generally along the lines of the converter and resonator 10 of Figure 1, comprising a canister or shell with an inlet end , forward portion , rearward portion , and outlet end The canister forward portion is actually divided into two separate portions, respectively and , each having a catalytic converter, respectively and , affixed therein, with each sealed about its periphery in the manner of the single catalytic converter 24 within the forward portion 16 of the converter and resonator combination 10 of Figure 1.
The two catalytic converter elements and may be spaced apart by a catalytic converter plenum disposed therebetween, if desired. Alternatively, the two converters and may be positioned immediately adjacent one another, in order to transfer heat generated by the catalytic reactions therein to one another for greater efficiency.
A catalytic converter and resonator plenum may be provided behind the second converter , in the manner of the converter and resonator plenum 52 of the converter and resonator 10 of Figure 1. Each of the catalytic converter elements and includes a substrate, respectively and These two substrates and are preferably formed in the manner described further above for the substrate 28 of the catalytic converter 24 of Figure 1, i.
A ceramic material, such as the Dow-Corning XT described further above, may be used to form the substrates and of the embodiment of Figure 2. It will be seen that additional catalytic converter elements, not shown, may be placed in series with the two catalytic converter elements and of the catalytic converter and resonator combination of Figure 3, if so desired, for further efficiency in processing exhaust emissions.
The rearward portion of the canister contains an axially concentric resonator tube or pipe element having a plurality of noise attenuating perforations therein.
The resonator element is affixed within the canister rearward portion by a forward and a rearward toroidal plate, respectively and , as in the converter and resonator combination 10 of Figure 1. A resonator plenum is defined between the resonator element and the canister rearward portion , similar to the equivalent construction shown in Figure 1. As in the catalytic converter and resonator combination 10 of Figure 1, the forward resonator tube retaining plate is preferably formed with a solid, impermeable periphery, to preclude exhaust gases from flowing directly into the resonator plenum from the catalytic converter and resonator plenum However, the rear retaining plate may be provided with a series of peripheral passages therethrough, in the manner of the rear plate 50 of the converter and resonator combination 10 of Figure 1, in order to allow any small amount of gases passing into the resonator plenum to escape therefrom.
The catalytic converter and resonator combination of Figure 3 functions essentially like the converter and resonator 10 of Figure 1, with exhaust gases G entering the canister through the inlet end , and thence passing through the two catalytic converters and The converters and The noise level of the exhaust is canceled or attenuated in a frequency range generally relatively higher frequencies according to the spacing and dimensions of the perforations of the resonator element The gases G then exit the catalytic converter and resonator combination from the rear or outlet end of the canister , to pass into the remainder of the exhaust system.
Figures 4 and 5 illustrate two further embodiments of the present invention, for dual exhaust systems having a pair of inlet pipes and a corresponding pair of outlet pipes. The catalytic converter and resonator of Figure 4, designated by the reference numeral , will be seen to have a single catalytic converter element therein, but includes a pair of resonator elements.
The catalytic converter and resonator is constructed somewhat along the lines of the converter and resonator 10 of Figure 1, comprising a canister or shell with an inlet end , forward portion , rearward portion , and outlet end However, it will be seen that the inlet and outlet ends and each respectively comprise a pair of laterally joined, truncated, conically shaped shells blending together to smoothly join the oval shaped canister portion The inlet and outlet ends and each have a pair of cylindrical inlet and outlet pipes, respectively and , extending therefrom.
These twin inlet and outlet pipes and allow the catalytic converter and resonator combination of Figure 4, to be installed in a dual exhaust system. The catalytic converter element of the converter and resonator combination of Figure 4, will be seen to have an oval configuration closely fitting within and sealed to the forward portion of the converter and resonator canister Thus, exhaust gases cannot pass between the inner wall of the canister shell and the outer wall of the catalytic converter element , but must pass through the substrate , as in the manner of the other embodiments.
The substrate of the catalytic converter element is preferably constructed similarly to the substrates 28, , and of the converter and resonator devices 10 and discussed further above, i. A catalytic converter and resonator plenum may be provided behind the converter element , in the manner of the converter and resonator plenum 52 of the converter and resonator 10 of Figure 1. The canister rearward portion contains first and second laterally spaced, axially concentric resonator pipe elements, respectively and , each having a plurality of noise attenuating perforations therein.
The resonator elements and are affixed within the canister rearward portion by a forward and a rearward plate, respectively and , as in the converter and resonator combination 10 of Figure 1. Instead of the toroid shaped plates of the catalytic converter and resonator combinations 10 and of Figures 1 and 3, the two plates and each have an oval peripheral shape, to fit closely within the oval shaped canister Each plate and includes a pair of laterally spaced apart resonator passages therethrough, for exhaust gases to pass from the converter and resonator plenum into the two resonator elements and , and from the resonator elements and.
A resonator sound attenuating plenum is defined between the first and second resonator elements and and the canister rearward portion , similar to the equivalent construction shown in Figure 1. The plenum of the converter and resonator combination of Figure 4 serves essentially the same function as the plenum 44 of the device 10 of Figure 1, i.
However, it will be noted that the plenum of the device of Figure 4 is somewhat larger than that of the other two converter and resonator combination devices 10 and described further above, since the surrounding canister does not encircle only a single resonator element. The resulting relatively large plenum may be desirable, with pressure waves from the two resonator elements and perhaps canceling one another in the central area of the plenum between the two resonator tubes and However, it is possible that amplification of certain frequencies might also occur under certain conditions, and accordingly, it may be desirable to divide the single large plenum with a longitudinal baffle shown as an optional component, in broken lines in Figure 4 in order to separate the two resonator elements and The baffle may extend forwardly of the forward resonator attachment plate , if so desired, to divide the converter and resonator plenum as well.
The forward resonator tube retaining plate may be formed with a solid, impermeable periphery, as in the catalytic converter and resonator combination 10 of Figure 1. However, an alternative is shown in the converter and resonator embodiment of Figure 4, in which both the front and rear plates and include a plurality of peripheral passages, respectively and , therethrough, in the manner of the rear plate 50 of the converter and resonator combination 10 of Figure 1, in order to allow any small amount of gases passing into the resonator plenum to escape therefrom.
The catalytic converter and resonator combination of Figure 4 functions essentially like the converter and resonator 10 of Figure 1, with exhaust gases G entering the canister through the dual inlet pipes of the inlet end , and thence passing through the single catalytic converter element While the single oval shaped converter element is generally shaped to fit more conventional catalytic converters, it will be seen that the dual resonator embodiment of Figure 4 could be constructed with the forward portion of the canister configured with two adjacent cylindrically shaped areas, to accept two laterally spaced cylindrical converter elements configured somewhat like the converter elements 24, , and of Figures 1 and 2, if so desired.
The converter element serves to react the exhaust gases G catalytically, whereupon the gases G pass into the catalytic converter and resonator plenum and rearwardly through the two resonator elements and The noise level of the exhaust is canceled or attenuated in a frequency range generally relatively higher frequencies according to the spacing and dimensions of the perforations of the two resonator elements and , and the installation of a dividing baffle if any therebetween.
The gases G then exit the catalytic converter and resonator combination from the rear or outlet end and corresponding outlet pipes of the canister , to pass into the remainder of the exhaust system. The axially parallel configuration of the inlet pipes , substrate passages of the catalytic converter element , dual resonator elements and , and outlet pipes , serve to provide the least possible change of direction for exhaust gases G flowing through the catalytic converter and resonator combination of Figure 4.
In fact, other than some mixing and expansion which may occur in the plenums of the device of Figure 4, the components of the two basic exhaust gas passages defined by each corresponding inlet and outlet pipe and , are precisely axially aligned with one another. Preferably, the canister shell , resonator elements and , forward and rearward resonator attachment plates and , and longitudinal resonator plenum baffle if installed are all formed of corrosion resistant stainless steel, although other materials may be used if desired.
The catalytic converter and resonator combination embodiment of Figure 5, will be seen to be similar to the converter and resonator combination embodiment illustrated in Figure 4 and discussed above, and closely related to the catalytic converter and resonator combination embodiments 10, 60, and , respectively of Figures 1, 2, and 3.
If you remove the resonator and all the rest of the exhaust system such as the muffler then there may be a slight increase in horsepower. An exhaust resonator is designed to reduce the drone, buzz, or even whine of your exhaust by attaching onto your muffler. While mufflers reduce the exhaust volume, resonators tune the exhaust for a more pleasant sound. Catalytic converters and resonators are often thought to be the same object, as they are both part of the exhaust system.
A catalytic converter does not reduce the amount of noise made by an exhaust system and a resonator does not reduce the toxic emissions of a vehicle. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Dissertation Where is the resonator located? Ben Davis March 11, Where is the resonator located?
0コメント