buzzing noise
 

I'm trying to figure out where I'm hearing this buzzing noise from. coming from under the car about in the middle. happens most at between 1500 and 2000 rpm in or out of gear and is louder under acceleration. below or above that range it's just a slight rattle and intermitent. It is worse when it's cold and sometimes gone competely once it's warmed up.

I hope these symptoms are detailed enough for someone to point me in the right direction. I was assuming something loose in the exhaust system but I've checked all of that and it seems fine. I thought maybe it was internal in the cat or muffler.

Recently on a Forester forum someone was mentioning their transmission being toast because of what they seemed to describe as a similar buzzing in the front diff. Is it possible that' where the sound is and how bad could that be? Any help would be great.

Elazar

Re: buzzing noise
 

From your description it really sounds like exhaust, possibly the heat shield on the cats or something. Get the front up in the air at least and have someone rev the engine while you listen.

Re: buzzing noise
 

Hi there, Had this myself - I am guessing that the resonator internals have come adrift. I ended up substituting a length of tubing which made the car very slightly noisier inside but no infernal buzzing which would have driven me nuts. I haven't bothered to cut the old one open but maybe this would cure the noise without extra sound inside the car - it is very robust so even without internals it would still do a fair job perhaps.
All the best, Steve.

Re: buzzing noise
 

It sounds like broken baffles in the resonator just behind the main catalytic converter. This is a very common problem with our cars. Do a search on resonators or buzzing noises to find out more.


After you cut out the old resonator, you can replace it with a universal 2.5" in/2.5"out resonator. Usually 4" in diameter and 14" long, such as a
Magnaflow 10416 http://www.performancepeddler.com/de...CT_ID=MAG10416

Their advertised price is $58.62, but you can make them a lower offer

or an

AeroTurbine AR25. http://www.aeroperformanceexhaust.com/products.htm

Thier price is about $51.75.


You can also just weld in a straight section of 2.5" exhaust tubing in place of the resonator. Many here have done that, but the resonator works the best for keeping undesirable resonances away.

.

Re: buzzing noise
 

Elazar

What you are describing here sounds almost 100% like the fizzle or rattle that happens when the internal baffle plates come loose in the resonator box.

You describe it as louder under acceleration and this makes it very likely to be your resonator baffles. I say this because it is accentuated by what's called 'sympathetic vibration'. The vibration caused when on the move gets amplified and when I had the problem on mine it was strongest at around 1850 rpm.

Some of these vibrations can also be caused by, or added to by loose heat shields between the exhaust pipes and the body.

This resonator is situated in the exhaust line almost directly below the handbrake. There are several possible cures for it.

1. Replace the resonator with a new one from Subaru.
2. Replace the resonator with a cheaper after market model.
3. Cut out the offending resonator box and replace with a straight piece of pipe.
4. Cut out the resonator. Cut it open at the seamed edge. Braze the loose baffle plates so they can't vibrate. Weld it back into position.

If you are on good terms with the nearest exhaust workshop the last one is the cheapest that will give good results.

Joe :)

Re: buzzing noise
 

Thanks all for the advise. That's what I was thinking. I'll probably just replace it with straight pipe. I had plans of redoing the exhaust anyway just not ready to shell out the cash for it right now. what is the resonator for and will I get any better exhaust 'notes' without it? boxer engines sound so great and I want to be able to hear it!

Re: buzzing noise
 

In my opinion it disimproves the sound to an unacceptable level. However I'm of the 'older generation' round here. :rolleyes:

If you are under 30 and have ever remotely considered that the bean can rear pipe on a ricer Honda Civic sounds or looks good, you may like it. :p

It makes the overall sound slightly louder, especially on acceleration. However, although I could live with louder, it also make the sound harder, like the blare off a two stroke bike. It seems to lose some of the deepness, there's no rumble in the sound any more.

You may like it, so it won't cost you much to try it. I advise you to retain the old resonator though, if you don't get on with the blare you might want to fix and refit the box.

BTW the resonator is there to aid the exit velocity of the hot gases. Taking it out of the exhaust line is sure to negatively affect low down torque, although I don't know of anyone on here who has ever done a dyno test, before and after, to verify the numbers.

If you fancy trying something new you might consider opening the resonator chamber and removing the loose baffles, then stitching it up and putting it back in the line. It will be louder than before, but the expansion will still aid gas velocity, and with any luck it won't sound like a wasp in a bottle.

Joe :)

[Old Fogey :tongue:]

Re: buzzing noise
 

John, I love your detailed replies! Always complete with references, links, prices, measurements...

Do you have a Six Sigma certificate or something?

Re: buzzing noise
 

Thanks for that info Joe. The "pissed off weed eater" sound is definitey not what I'm going for. I am only 24 but aside from the SVX I'm more of a muscle car type guy myself and that torquey rumble is what I'd really like to get.

I know this would be another thread but does anybody have any tips for improving the sound how I want? Or maybe directions to any existing threads?

Re: buzzing noise
 

I'm the same Elazar. I would have no problem with it being way louder, so long as it is deep, or deeper than OEM.

People like the Stebro sound, that means changing the back box. Also Tom svxfiles does a great upgrade, you should contact him.

Like John suggests above, do a search for resonator or for buzzes, you'll pull up the threads, they are all a ways back.

You might consider doing what I suggested as the last option. Remove all the baffles from the OEM rattly resonator, then close it up and weld it back in place. You might end up with a louder SVX which many would like to have, plus if the sound retained some rumble, everybody would be doing the mod!! :bash:

Joe ;)