Choosing exhaust parts for REALLY quiet

[jmgtp]

I'm looking to weld up a new exhaust over the winter since my current one was frankensteined together during my motor swap. The goal is new car quiet. Not 3.1 GenII quiet, but stock Chevy Malibu 3500 quiet.

Right now it has:
3400 exhaust manifolds
2.5" downpipe (modded 3.4 dohc dp)
2.5" converter (new Walker 3 way)
no resonator (I have one from an L67 but it might be too long to fit the car)
L67 Grand Prix Mufflers (cans are too big and hit the body on bumps, they gotta go)

It isn't loud but it isnt quiet either. It sounds like a stock GenII 3.1 but a touch louder. I want it to sound like a stock Chevy Malibu 3500 (this is the engine in the car).

Is the secret all in the mufflers and resonator combination or is there more to it?
Replacement suggestion for these parts? I'm thinking of sticking with 2.5" pipes since that is what I have but I wouldnt care if the mufflers necked down to 2.25" or even 2" (unless going down to 2" would really kill performance). This is a daily driver and I'm primarily interested in quietness, low end torque and mpg.

[Superdave]

Exhaust systems on newer cars are engineered to be as quiet as possible by exact placement of the cats, resonators, mufflers and even the exhaust tips, varying diameter of the pipes and ID of the components. They specifically "tune out" the frequencies and what you end up with is a weird wind blowing sound out the back.. lol


If you want it to be really quiet you're going to have to add in at least 1 resonator about 3/4 the length of the system, then use something like a pair of Walker Quiet-flow mufflers out back or even a pair of mufflers off of a newer 60v6 GM car.

[TGP37]

Drop in a turbo, that will quiet up the exhaust, lol.

[bob442]

Yeah, having a resonator and a baffled muffler will quiet it down

[jmgtp]

I think I found a set of Walker Quiet Flows for a decent price and I have an L67 resonator that may fit or I may end up buying a new one that is a bit shorter if it turns out too big.
Are these mufflers as quiet as their name suggests? At least OEM equivalent is what I'd be looking for.

Would 2" pipes after the Y be detrimental? The mufflers I found are 2" in/out. I'm thinking it should be fine (again, daily driver not performance build), the system would be 2.5" into the Y and 2" out.

[geoffinbc]

If it is possible buy pipe with a thicker wall than the typical cheap stuff. Stainless, if you can afford it, will also absorb sound better. You can also wrap the exhaust system to help out.

[Superdave]

Dual 2" is not a problem, Still plenty of flow there.

[RedZMonte]

Stock 00+ bonneville SSEI exhaust would be a good system to modify if your looking for good flowing, quite. my car sounds healthy but not loud one bit. has a medium size resonator and flatter mufflers compared to a GP. '02+ has 2.25" Y-back, '00-01 is 2" Y-back.



This is a bonneville guy on the bonneville club that has a ton of bonnie parts, may be able toget the muffs and res cheap.

http://www.andrewsuderman.com/bonnevilleparts.html

[jmgtp]

Not sure I want to chance spending on Bonneville mufflers that might not fit. The Walker Quiet Flows are OEM replacement and use stock hangers, pretty much a guaranteed fit. Only downside is they are aluminized steel rather than stainless but they should still last for a while since the car isnt winter driven.

In conjunction with the Walker mufflers, I think the key to quiet, like others have said, will be the size of the resonator that I use. I'm going to move the cat as far foward as I can and then use a good size resonator. Hopefully the resonator I have off
an L67 GP will fit - it is long. I think it may only be 2" diameter, but honestly if that was good enough for a 240hp L67 it will be more than good enough for my modest 3500. I might add a second smaller resonator or glass pack in the straight section of pipe that goes around the gas tank to further tone it down. The closer I get to what I call "new car quiet" the better.

I need the car for at least the next month or two (holding out driving the gas guzzler truck until snow is on the ground) and then it will go under the knife again for exhaust work, a/c conversion and cleaning up the things that I rushed during the motor swap. Namely coolant hoses, some of the wiring and the throttle cable bracket.

[woody90gtz]

I have headers and full 2.5" mandrel exhaust, but it is still super quiet at idle and light cruise with my Dynomax VT. At wide open it is just as loud as a Dynomax UltraFlo though. Nice for a sleeper that you still want to hear when you get on it.