Newbie question about cat

[Jonsku]

So, I've '89 325 with cat. I'm just wondering what are those two cylinderical things that are between the motor and cat. I'm making new exhaust, is it possible just to use cat and rear muffler and not to care about those two thingies?
Thanks for your answers in advance.

[KenC]

Two cylindrical things? Do you have a picture?

[Jonsku]

Nope, I think they are kind of pre-cats or something.. I'll try to find a picture on net.



In this picture there are four of those cylinderical thingies, I've two of those (one in each pipe) before the cat. Mine are smaller than in this pic (pic of S50 in E30 I think) :)[/img]

[Rich V]

The two closest to the engine are the cats, the two behind them are the resonators.

[Jonsku]

Can those resonators be before cat? Guess not, on other forum ppl said that they would be kind of flame killers, so that the cat wouldn't burn. If they are flamekillers, I guess it'd be better to save 'em, but if they are resonators then they can be forgotten.
Am I figuring this out right?

[nando]

flame killers?

they are resonators.. what other forum are you going to? www.caridiots.com? :P

[Jonsku]

Hey come on, I told you I'm a newbie :oops:

Anyways, can resonators be b4 cat? If they are, is there difference other than in sound?

[e30Matt]

Resonators are almost always behind the cat.

And there is such a thing as a "flame killer", but it's called a flame arrestor.

[M-technik-3]

Resonators are almost always behind the cat.

And there is such a thing as a "flame killer", but it's called a flame arrestor.

Commonly seen on airfields where fumes and vapors are everywhere.

[e30Matt]

Resonators are almost always behind the cat.

And there is such a thing as a "flame killer", but it's called a flame arrestor.

Commonly seen on airfields where fumes and vapors are everywhere.

:up: Also commonly found on boats where the vapors can be trapped under decks.

[M-technik-3]

Ahh, on Gas type right? no need for on a diesel.