Resonator

[svxfiles]

Originally Posted by Gamesy

that would explain why when my resonator is rattling i have **** for power but once it stops ratting its like V-tec kicks in lol

Nope, no, no.
Its your tranny.










































I'm kidding!

[Bonestock]

Originally Posted by oab_au

Well in my fairly vast mechanical experience/knowledge, I have to completely disagree with you.

Freeman is right. The 'Resonator' is a vital piece of the exhaust system. It acts as the expansion area for the gas plug from the cylinder to drop pressure in. It also is an expansion point for the sonic wave to reflect back to the cylinder as a negative pressure. Without it the engine looses a lot of torque.

It should be replaced with a Resonator of the equivalent volume.

Harvey.

I am going to have to disagree with you too Harvey (in a happy non-condescending manner-- hint hint lol). The main purpose of the acoustic resonator in our exhaust is for SOUND and nothing else. Its not there for a scavenging effect if that is what you are hinting at. You get all the back pressure the engine could ever need with those cats and terrible muffler design. If you wanted to equalize the exhaust pulses it would be done MUCH closer to the exhaust manifolds in the form on an H-pipe or X-pipe.

I think you are confusing the automotive resonator with an expansion chamber found on two strokes.

[svxfiles]

Originally Posted by Bonestock

I am going to have to disagree with you too Harvey (in a happy non-condescending manner-- hint hint lol). The main purpose of the acoustic resonator in our exhaust is for SOUND and nothing else. Its not there for a scavenging effect if that is what you are hinting at. You get all the back pressure the engine could ever need with those cats and terrible muffler design. If you wanted to equalize the exhaust pulses it would be done MUCH closer to the exhaust manifolds in the form on an H-pipe or X-pipe.

I think you are confusing the automotive resonator with an expansion chamber found on two strokes.

Bonestock, I understand your scepticism, and normally would agree with your general statement.
However, this being an SVX, with an engine that actually works like a pair of three cylinder engines sharing a common crankshaft, an X pipe or balancing is not necessary, or helpful.
I have had about fourteen(?) custom exhausts on my Claret, always in search of "The Perfect Exhaust".
and, as Harvey stated, its sure hard to better the exhaust over stock!

I have removed the factory resonator and not noticed the differance,
BUT several customers with multiple SVXi have,
to the point that they insisted on the re-installation of a resonator.

Who am I to argue with someone who only drives one or two SVXi...
AND REALLY pays attention! John.

[oab_au]

Originally Posted by Bonestock

I am going to have to disagree with you too Harvey (in a happy non-condescending manner-- hint hint lol). The main purpose of the acoustic resonator in our exhaust is for SOUND and nothing else. Its not there for a scavenging effect if that is what you are hinting at. You get all the back pressure the engine could ever need with those cats and terrible muffler design. If you wanted to equalize the exhaust pulses it would be done MUCH closer to the exhaust manifolds in the form on an H-pipe or X-pipe.

I think you are confusing the automotive resonator with an expansion chamber found on two strokes.

No problem, we will find agreement somewhere.

Your last statement is exactly right. The resonate chamber is doing the same sort of job, in reflecting the sound wave back to the cylinder.

This bit gets a definite no.

You get all the back pressure the engine could ever need with those cats and terrible muffler design.

This is a myth that the engine needs a positive back pressure. What the engine needs is a negative pressure, returned to the cylinder, that produced it. It gets this from the resonator's, reflecting wave.

The rear muffler is not as restrictive as you may think, judging from the quite exhaust note. It is quite, because all the sound energy has been used up in improving the negative pressure in the cylinder, the rest has got lost in the huge muffler.

Harvey.

[Trevor]

Originally Posted by oab_au

No problem, we will find agreement somewhere.

Your last statement is exactly right. The resonate chamber is doing the same sort of job, in reflecting the sound wave back to the cylinder.

This bit gets a definite no.


This is a myth that the engine needs a positive back pressure. What the engine needs is a negative pressure, returned to the cylinder, that produced it. It gets this from the resonator's, reflecting wave.

The rear muffler is not as restrictive as you may think, judging from the quite exhaust note. It is quite, because all the sound energy has been used up in improving the negative pressure in the cylinder, the rest has got lost in the huge muffler.

Harvey.

There is no “sound wave”. There is no “sound” energy. There is no backwards reflection of “sound”. The fact that pulses of gas exiting a pipe make a noise is of no consequence. There is no sound until the exhaust gas directly enters the atmosphere, or has caused the system to vibrate.

Everything depends on the energy produced as a result of the velocity and the number of packages of gas travelling down a conductor at a given point in time. Each moving package of gas creates a followng package of low pressure gas. Nothing is “reflected” back, everything is ongoing. There is a train which has innertia travelling down a line and power is available which can be utilised.

Therefore the dependant factors within a four stroke engine constitute. --- engine speed; valve timing; number of cylinders feeding a given conductor; effective conductor cross section; resistance as a cosequence of shape or texture; when where and if individual outputs are combined; length of the conductor prior to any area providing substantial expansion; resistance from that point on.

A chamber providing expansion prior to the muffler, provides the first step in an evolving process. The muffler system, muffles the impending sound vibrations before these enter the atmosphere by smoothing the high and low energy peaks available between pulses. A factor of time is involved in respect of each pulse of energy negotiating the muffler before exit, and the rate and speed is modified. Inevitably this must incur some resistance.

[Blacky]

Now that I can sink my teeth into.

[Sean486]

I am thinking I may have this done at some point. Probably couldn't hurt and I have never been completely happy with exhaust sound without the resonator. Has anyone used the one that Dayle is selling?

http://svx-motorsport-accessories.st...svxhiflre.html


Oh and Trevor, I really respect your opinions, but I'm sorry I feel a bit lost every time I read one of your posts. Can you dumb it down for me a bit. Are you saying you agree that the SVX should have the resonator as a important part of the exhaust?

[icingdeath88]

Originally Posted by Sean486

I am thinking I may have this done at some point. Probably couldn't hurt and I have never been completely happy with exhaust sound without the resonator. Has anyone used the one that Dayle is selling?

http://svx-motorsport-accessories.st...svxhiflre.html


Oh and Trevor, I really respect your opinions, but I'm sorry I feel a bit lost every time I read one of your posts. Can you dumb it down for me a bit. Are you saying you agree that the SVX should have the resonator as a important part of the exhaust?

It's hard to tell what exactly the conclusion is supposed to be, but I think he's saying the resonator is a good thing, just explaining it in a completely different way from Harvey. Also he's disagreeing with Harvey and saying the muffler is restrictive.

[Freeman]

Restrictive? Wait, what?

And that one from Dayle looks nice. Nice price on it too

[Bonestock]

I believe Trevor is explaining in depth what I am talking about. The resonator in the exhaust is there for no reason other than altering the exhaust "note". Altering can be many things but usually the presence of a resonator in a cars exhaust QUIETS the overall db and or/helps eliminate certain frequencies the designers deem undesirable.

Now for a few of the other comments. One can not simply state (as fact no less) that you can not remove a part of the exhaust system w/o replacing it with a part of equal shape design or volume. That goes against every MFG, tuner, race team or whatever expertise you want to mention.

Since our engines are basically air pumps, the more air you can get into it & out the more power it will make (with the appropriate amount of fuel obviously). Now I am not saying you can strap a sewer pipe to the intake and exhaust since the air must still travel thru the engines intake, combustion chamber and onto the exhaust ports etc. Its all about proportion on N/A engines. Sure you can shift the power about with different type of manifolds, headers, pipe diameter etc. It just depends on if the engine can benefit from the changes ie allows the exhaust gases to exit more efficiently. And increasing efficiency is called improving the engines VOLUMETRIC EFFICIENCY. I can not see how the addition of a resonator can have any effect on the engines performance providing it does not change flow +/- by any significant degree. I guess I should also note that when referring to exhaust back pressure its really a misnomer since we are really talking about maintaining exhaust velocity (to aid in expelling the burnt mixture as well as help draw the air and fuel into the combustion chamber ie scavenging like I mentioned before).

I may only have one SVX but I have been in the automotive world on both personal and professional level for quite some time now.

Oh and I guess I should throw in the obligatory hugs and kisses so no one takes offense.

[oab_au]

Originally Posted by Trevor

There is no “sound wave”. There is no “sound” energy. There is no backwards reflection of “sound”. The fact that pulses of gas exiting a pipe make a noise is of no consequence. There is no sound until the exhaust gas directly enters the atmosphere, or has caused the system to vibrate.

Everything depends on the energy produced as a result of the velocity and the number of packages of gas travelling down a conductor at a given point in time. Each moving package of gas creates a followng package of low pressure gas. Nothing is “reflected” back, everything is ongoing. There is a train which has innertia travelling down a line and power is available which can be utilised.

Therefore the dependant factors within a four stroke engine constitute. --- engine speed; valve timing; number of cylinders feeding a given conductor; effective conductor cross section; resistance as a cosequence of shape or texture; when where and if individual outputs are combined; length of the conductor prior to any area providing substantial expansion; resistance from that point on.

A chamber providing expansion prior to the muffler, provides the first step in an evolving process. The muffler system, muffles the impending sound vibrations before these enter the atmosphere by smoothing the high and low energy peaks available between pulses. A factor of time is involved in respect of each pulse of energy negotiating the muffler before exit, and the rate and speed is modified. Inevitably this must incur some resistance.

What a load of unmitigated crap.,

http://www.subaru-svx.net/forum/show...+system+design

http://www.subaru-svx.net/forum/show...+system+design

http://www.subaru-svx.net/forum/show...+system+design

Harvey.

[Trevor]

Originally Posted by Bonestock

I believe Trevor is explaining in depth what I am talking about. The resonator in the exhaust is there for no reason other than altering the exhaust "note". ---------

My post has not been correctly assimilated.

The resonator is there for a very definite reason, as was covered in my explanation covering the function of the exhaust system. The resonator is the first area providing substantial expansion and effectively ends the “tuned" portion of the system.

“Therefore the dependant factors within a four stroke engine constitute. --- engine speed; valve timing; number of cylinders feeding a given conductor; effective conductor cross section; resistance as a consequence of shape or texture; when where and if individual outputs are combined; length of the conductor prior to any area providing substantial expansion; resistance from that point on.”

A “tuned” exhAust system will certainly improve the volumetric efficiency of an engine. By this means, existing unused energy generated by a moving gas, is effectively harnessed.

[Trevor]

Originally Posted by oab_au

What a load of unmitigated crap.,

http://www.subaru-svx.net/forum/show...+system+design

http://www.subaru-svx.net/forum/show...+system+design

http://www.subaru-svx.net/forum/show...+system+design

Harvey.

A hollow obscenity, which in no way alters the correct information I have provided. However, it is very effective as a conclusive means of accurately illustrating the exact character of its author.

[Bonestock]

Originally Posted by Trevor

My post has not been correctly assimilated.

Thats because they are acoustic resonators on our cars and not expansion chambers (and I cant be bothered to get into wave dynamics) like those fitted to 2 stroke motorcycle engines etc.

The different sized resonators in the exhaust system are to change the exhaust note by canceling out certain frequencies (each size will have different effects) or to reduce the overall db .... nothing else.

And before this turns into a pissing match, and it will, thats all I have to add to the subject.

Hugs and kisses

[Trevor]

Any section within an exhaust system whereby the cross section is increased for a short distance, must constitute and work as an expansion chamber, i.e. a place where the gas flow can and will expand, no matter what.