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Resonator - Is it important?

02-20-2007, 12:16 PM
I understand that the Geo Metro had/has a "Resonator" somewhere on the
exhaust pipe....

What does one look like and is it an important thing to have there?

My exhaust pipe was "re-worked" by one of the previous owner(s) to just a
pipe and muffler. (Montanan's)

My Metro sounds like a sports car - kids would like it!

Is the resonator important and where does on obtain them?


02-20-2007, 04:43 PM
"My Metro sounds like a sports car - kids would like it!
Is the resonator important...?"

Your first statement provides the answer to the question you posted: it's about keeping the exhaust quiet...

In theory, the resonator's dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.

As to where to source one, I'm unsure.

02-20-2007, 09:06 PM
My resonator is on the intake side, it's a little rubber bowl (maybe 4 inches in diameter, 2 inches in depth) that fits on bottom of the intake snout on the breather. I had no idea what it was and posted a 'what's this?' question here over a year ago and got the following information:

The Question: 'One other thing, while I'm making a post anyway. On my 1.3L, there is a round device attached to the front of the timing chain cover at the top and it is loosely attached to the air inlet hose...what is this device? If you've seen it you know what I'm talking about. It doesn't serve any purpose that I can see..'

The Answers (condensed): 'that part on air cleaner is a silencer to quiet noise of air going into engine' and also....'Just to be more precise... as the intake valve opens a small portion of combustion gases forces itself into the intake charge before it quickly reverses and only then can the intake charge enter the cylinder. This creates quite a bit of noise in four and less cylindered cars. In six cylinder or higher cars there is more pulses that cancel out most of the noise. It is just a way of adding more volume to the intake sytem to help minimise noise.

SO...Thats the only resonator I know of. It is more noisy if you leave it off, similar to running it without a breather at all. I can't see where there would be any harm in leaving this attachment off aside from intaking some engine compartment air...

Hope this helps. If not, at least you're more informed :rofl:

02-21-2007, 12:01 AM
the resonator is on the EXHAUST pipe. its supposed to be about a foot back from where the front pipe joins the rear pipe under the car. its about 5" in diameter and 18" long. looks kind of like a cherry bomb muffler if you know what one of those are. without it exhaust is a lot louder

02-21-2007, 09:13 AM
THAT explains it! My Metro doesn't have one - just a pipe to the muffler!

Those bozo's in Montana took out the Catalytic Converter and put in a straight
pipe to the muffler.

I had the muffler changed and the muffler shop never said squat about a

Probably didn't know it was supposed to have one!

Would Schuck's or NAPA sell them?


GM Line Rat
02-21-2007, 08:23 PM
Those bozo's in Montana took out the Catalytic Converter and put in a straight pipe to the muffler.

I assume there is NO emmisions testing in your area....Huh Doc?......Mine either!....:grinyes: .

02-21-2007, 08:40 PM
No there is no emission testing for where I live (30 miles out of town), but I
hear rumors that the gubment is considering extending the testing to the whole

I actually expected one day to have to have a Cat Converter (CC) put on....

I suppose that a CC would act as a resonator, actually!

If I keep getting bashed by butt-headed drivers, though, a CC won't do much good.

I should weld "L'" stock steel bars all around The Phoenix rename it The Iron Lady and just drive that!

When doofusses back into me they'll get the butt end of the damage!


02-21-2007, 10:30 PM
DoctorBill, I just went through the resonator hassle with my 1995 Metro. I found one at for $69.95 including shipping. I decided not to buy it because I have no welding skills or equipment. The part name is "exhaust pipe" and the part number is WK46928. The brand is Walker. The part description is "resonator/pipe assembly". It goes from the exhaust manifold pipe back to the muffler. Of course, the part number for a 1992 may be different. I decided to go to Midas, instead, and it was expensive. The charge was supposed to be $125.99, but they neglected to tell me that a new muffler would be reguired because they had to cut it off to make room for the new assembly. They didn't charge for the muffler, just $40 more for labor. My old muffler was only three years old, so I didn't gain much.

Good luck.

GM Line Rat
02-22-2007, 01:38 AM
Doc, My 94 4 Dr Metro still has the Cat, Muffler and resonator on it for now....When it rusts out, I'll put as quiet a muffler on it as I Can.....But that's about it. My 95 Caprice (LT1 Motor) has what they call "Export Pipes" on it (Cat delete pipes) that flow into a set of flowmaster Delta Flow mufflers and I deleted the resonators too.....Nice low end rumble with little exhaust drone at idle but it gets fairly loud when you "Nail It". Wont pass any emmisons tests without the cats....Wife hates it which means.....I love it!......:lol: .

04-07-2007, 12:55 PM
Hi, new guy here drudgin up old posts! Anyway, as far as the resonator goes, You can use a glasspack or cherrybomb type muffler. It works best if you use the cherrybomb type with the metal baffles, as glasspacks will eventually wear out. It shouldn't cost much for the muffler, I've seen some on ebay for around $20 shipped, then an exhaust shop worth it's salt should be able to put it on quickly for around $25-30.

Is it required to have a resonator? Only from an emissions standpoint. Even then, it's just there to make it quieter.


04-08-2007, 10:28 AM
My two cents:
When I bought my 93 Geo 1.0L 5 speed, the previous owner had eliminated
the catalitic converter & the resonator & just had a muffler. I live in an
emissions testing area & in order to get it to pass, I had to install the cat
& resonator. My mileage went down 3 - 4 MPG. Appearantly (according to
the tech at Midas) the cat & resonator create "back pressure" which lowers
your MPG. If you don't need it for emissions, I suggest you leave it alone.

04-14-2007, 09:49 PM
I just had my whole system replaced @ 2". They only put a muffler on. I hate the sounds, it's like a weedwacker! But, the power and economu have both gone way up.

Doc, what size pipe is on yours?

04-19-2007, 03:23 PM
Yet another 2 cents. I took out my cat, and kept the resonator. Power went up, efficiency improved a bit, and the sound is quite reasonable. Definitely louder, but not too much. The cat is a good device to decrease co2, co and nox. It only does that if it is replaced when it has become clogged, or filled up. I assume most people don't replace it periodically, so it isn't doing the good it was intended. It's an interesting question, is the decreased emissions by using a cat better than the decreased amount of gas one would use if there is no cat, due to the improved efficiency? One must wonder...


07-04-2007, 11:37 AM
I found this thread because I had the same question "what's the resonator for?". My '95 Metro 1.0L has a single Cat, then downstream just a muffler - no resonator. Reading posts in this thread makes me think a previous owner had the original resonator/muffler combo replaced by just a muffler.

I'm going to pursue getting it back to stock parts. Here's some pertinent text from the '95 repair manual:
The Geo Metro exhaust system consists (from front to rear) of an exhaust manifold, a warm up three way catalytic convertor (WU/TWC) (if equipped), an exhaust manifold heat shield, a front pipe/three-way catalytic converter assembly and a resonator/muffler/tail pipe assembly. Various flexible rubber hangers suspend the system along the underside of the vehicle.

A resonator is used on all models of the Geo Metro. It allows for the use of mufflers with less back pressure and provides for more effective exhaust system tuning characteristics. The resonator is serviced as part of the resonator/muffler/tail pipe assembly.

07-05-2007, 11:10 AM
I just replaced the resonator on my 98. It is part of the rear exhaust pipe behind the catalytic converter. The whole assembly is about 3 foot long. It was $45 from NAPA. Why monkey around with work around solutions for that price?

07-06-2007, 11:54 AM
When I bought my 93 Swift last year it was making a rattling sound at certain RPMs. Using a broom handle I banged on the resonator and found the rattle was coming from inside. I cut it in half with a hack saw and found the tube inside was broken off and rolling around. The resonator looks like a small muffler, about a foot long. It's empty except for a steel tube that sticks into it about 8 inches from the outlet side. I removed the tube and welded it back together.

The result is that the exhaust has a bit of a growl that is absent on cars with a working resonator. Power and fuel mileage don't seem to be affected.


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