what is an exaust resonator?

[GasSavers_Ryland]

I just picked up a 1983 Civic Hatchback DX, and the only thing it seems to really need is a muffler, and a transmision, the exaust pipe has been replaced most of the way back with some of that stupid clamp on piping, looks to be 1 3/4 or so tubing going all the way back to the muffler, when I've replaced exaust pipe on other cars, some where around the middle of the car they have what is labbled as a Resonator, and after the resonator the tubing size steps down, but what is this resonator? is it just a little muffler?
If I find a small muffler (tractor muffler?) that I can stick inline, should I then reduce the size of the exaust pipe further back, thus keeping exaust velosity up?

when I get this car running well enough to be reliable I'll most likely sell my stock 1985 CRX HF with it's spare HF engine and tranny, so keep your eyes out in the coming months!

[omgwtfbyobbq]

Depending on the engine/exhaust, the car may have a resonant frequency that's kinda displeasing to most drivers. The factory will put a resonator in to kill or change this, so the resonant frequency is either much higher in the pm/speed band and gets masked by other noise, or dissappears completely. It's not a muffler, just a change in the exhaust shape to kill any reinforcement sound waves may get at some speed. W/o one, the car may be noticeably louder at some speed/rpm. My vw exhibited this when I put a glasspack where the resonator was after the entire exhaust rotted through before it, it's quiter at 65mph compared to 55mph.

[budomove]

mmmmm. just saw this site. pretty cool.

http://www.1stgencivic.com/forum/viewforum.php?f=31o

[onegammyleg]

Originally Posted by omgwtfbyobbq

Depending on the engine/exhaust, the car may have a resonant frequency that's kinda displeasing to most drivers.

Exactly rite

A resonator is to reduce the effects of exhaust pipe resonance , the obnoxious loud droning sound (not the wifes voice) that is loudest at one particular rpm.

A resonator is usualy of straight through design with no fiberglass absorbtion material inside.
Aftermarket ones often look like hot dogs , while oem types may look like a normal muffler.
The are usualy placed in the middle of the pipes length which will aproximately double the rpm that the resonance is heard at.

[bones33]

This link has a calculator that will help you place the resonator (or any other exhaust pipe diameter change) where you want it.
http://www.nightrider.com/biketech/c...austlength.htm
It applies to all ICEs not just harleys.
That droning at a specific RPM is a sweet-spot of the exhaust system. Tune this in conjuction with the intake length and volume and the rest of the engine and you'll have a good little boost of engine efficiency. Exhaust diameter changes usually take place in several places - header, resonator, muffler, end of tailpipe and other places where diameter changes. Use these to your advantage where possible, like where you spend most of your time on the freeway, AND where you need maximum power.
Megaphones have a continuum of diameter changes so the sweet spot is over a larger RPM zone, but they are not really useful on the street due to noise.

[JanGeo]

On my Geo is was in the middle of the car exhost system and was made by welding a bunch of metal pieces together in a weird shape - all stainless of course but once welded with non-stainless rod it rusted out on all the welds. Once I bypassed it the exhost note got really snarly and the car ran a LOT better.