Resonators
Thread Starter
2nd Gear Member
Joined: Sep 2006
Posts: 288
Resonators
I am looking for some resonator selection tips from people who have experience with this...As far as material of construction is concerned, I know stainless steel is ideal for longevity.
I am more interested in how the size of a resonator effects the sound. Will longer resonators reduce the volume more, since they have more baffling material?
Does the length of a resonator effect how much deeper it makes the exhaust?
Here are some possibilities I have found:
AERO
http://stores.channeladvisor.com/ver...ts/Items/AR25?
VIBRANT
http://stores.channeladvisor.com/ver...ts/Items/1792?
DYNOMAX
http://store.summitracing.com/partde...5&autoview=sku
BORLA
http://store.summitracing.com/partde...5&autoview=sku
Some of these are shorter than others....OAL is less important than the case length I would guess since the actual packing is only in the case.
5th Gear Member
Joined: Mar 2006
Posts: 2,544
From:
RE: Resonators
A resonator reduces sound three ways.
First, as you mentioned, it contains packing and/or baffles, like a muffler. In this case, a longer resonator will generally be quieter than a shorter one (assuming similar design).
Second, the resonator breaks up the length of exhaust piping. This means that instead of one resonant frequency, the pipe now has two. This is good--it means that instead of a single, loud, drone peak there are now multiple--but quieter--peaks. In this case the size of the resonator doesn't matter. What affects this is WHERE the resonator is place.
Third, the resonator acts as a Helmholtz Resonator (google that, I can't possibly describe it here) which will cause destructive interferance at certain frequencies.
I would say the #1 factor is item #2 above, where you locate the resonator. Ideally you want the two lengths of pipe to be different, but not even multiples of each other.
Any pipe that is resonant at a given frequency is also resonant at even multiples of that frequnecy. So a pipe that's resonant at 1200 hz is also resonant at 300, 600, 2400, and 4800. That means that if you place your resonator exactly in the middle of a pipe, you haven't done much good becasue now you've got two halves with the exact same resonance characteristics as each other. What you want is to divide the pipe into two lengths that are not even muliples of each other. That way the resonance characteristics of each pipe-segment interferes with the other--that is what kills drone most effectively.
Examples:
half-half is bad as the aforementioned example described.
1/3 - 2/3 is bad becasue 2/3 is exactly twice 1/3.
2/5 - 3/5 is good becasue there is no common ground between the two lengths.
Bottom line: I would pick a resonator based on fitment and material. Then, choose the best place to install it. There isn't that much leeway on our cars but you can hit the 2/5-3/5 example pretty damn close.
First, as you mentioned, it contains packing and/or baffles, like a muffler. In this case, a longer resonator will generally be quieter than a shorter one (assuming similar design).
Second, the resonator breaks up the length of exhaust piping. This means that instead of one resonant frequency, the pipe now has two. This is good--it means that instead of a single, loud, drone peak there are now multiple--but quieter--peaks. In this case the size of the resonator doesn't matter. What affects this is WHERE the resonator is place.
Third, the resonator acts as a Helmholtz Resonator (google that, I can't possibly describe it here) which will cause destructive interferance at certain frequencies.
I would say the #1 factor is item #2 above, where you locate the resonator. Ideally you want the two lengths of pipe to be different, but not even multiples of each other.
Any pipe that is resonant at a given frequency is also resonant at even multiples of that frequnecy. So a pipe that's resonant at 1200 hz is also resonant at 300, 600, 2400, and 4800. That means that if you place your resonator exactly in the middle of a pipe, you haven't done much good becasue now you've got two halves with the exact same resonance characteristics as each other. What you want is to divide the pipe into two lengths that are not even muliples of each other. That way the resonance characteristics of each pipe-segment interferes with the other--that is what kills drone most effectively.
Examples:
half-half is bad as the aforementioned example described.
1/3 - 2/3 is bad becasue 2/3 is exactly twice 1/3.
2/5 - 3/5 is good becasue there is no common ground between the two lengths.
Bottom line: I would pick a resonator based on fitment and material. Then, choose the best place to install it. There isn't that much leeway on our cars but you can hit the 2/5-3/5 example pretty damn close.
Thread Starter
2nd Gear Member
Joined: Sep 2006
Posts: 288
RE: Resonators
I already purchased the Vibrant ones (which also happen to be the shortest of the bunch with a case length of 9.5", compared to 10" for the Aero, 12" for the Dynamax, 14" for the Borla's).
I was hoping the resonator might quiet the exhaust down a little, but am afraid the one I got is too short....or do you think there won't be a huge difference among these choices?
I was hoping the resonator might quiet the exhaust down a little, but am afraid the one I got is too short....or do you think there won't be a huge difference among these choices?
Thread Starter
2nd Gear Member
Joined: Sep 2006
Posts: 288
RE: Resonators
I have an appointment to get them installed tommorow, going to install them in the location indicated in the attachment. Everyone else seems to have had success installing them here (and I am not sure there is anywhere else to do it). I am guessing as far foward as possible, otherwise it looks like you might just be splitting the pipe in half (from cats to resonator and from resonator to mufflers).
[IMG]local://upfiles/49501/4A6E5DD49D634E58B8E9BB7F8878D2CD.jpg[/IMG]
5th Gear Member
Joined: Mar 2006
Posts: 2,544
From:
RE: Resonators
Yeah, that's the only real spot you can put them on these cars.
Ideally, get a flexible measuring tape (like the kind used for fitting clothing) and measure from the manifold back to the tailpipe, following the curves of the exhaust as you go. Take that total measurement, divide it into fifths, and try to put the resonators at the 2/5 - 3/5 split. It may not be perfect, but you should have several inches of room to play with.
Ideally, get a flexible measuring tape (like the kind used for fitting clothing) and measure from the manifold back to the tailpipe, following the curves of the exhaust as you go. Take that total measurement, divide it into fifths, and try to put the resonators at the 2/5 - 3/5 split. It may not be perfect, but you should have several inches of room to play with.
