FAQ: The Exhaust Thread

the other difference is T304 is nonferrous - meaning it wont' rust the same way the common stainless for exhausts does. It also will take a polish (probably due to nickel content but I am not sure).

Albertj

I think he meant "409" instead of 403. That's common for stainless exhaust components. It's relatively cheap, and heat resistant. The only downside is that it will form a light surface rust after a while, which prohibits further oxidation.

304 costs more for the benefit of no surface rust. That's about all you get for the extra money.

If you really like spending money, go with the best - 321.

OK, next question please - all other things being equal in a given exhaust system, what changes in tone happen when a longer resonator is swapped in for a shorter one (assuming same construction, straight thru pipe)?

Albertj

albertj wrote:

OK, next question please - all other things being equal in a given exhaust system, what changes in tone happen when a longer resonator is swapped in for a shorter one (assuming same construction, straight thru pipe)?

Albertj

noisier, less deep sound

I witnessed almost exactly that scenario on a 4cyl ranger

what about a larger diameter but same length resonator. For example, if I were to replace the stock center post-cat piping with 3", and used a 3" resonator of the same length (I'm thinking 6" chamber)?

update:

I decided to install sound deadening material in the trunk, but could not find any locally and don't have any trips to say Rochester coming up. So I tried a roll of vinyl stair tread material. It's not Dynamat but it does work. Reduces the resonance a lot.

I also added some fiber padding (similar to what's under the trunk carpet) to the molded side panels in the trunk.

At some time in the future I can pull the vinyl out and put DynaMats in... but what I did dampened noise pretty well. We'll see - am on the highway again Sunday.

Albertj

I took videos yesterday ( Sunday ) and posted them on YouTube. One is a cold start-idle-rev sequence and the other is a driveby sequence. My YouTube id is TheAlbertj. (surprised?) If the link does not work you can find 'em that way.

Please tell me what you think of the sound.

First video is a cold start - revving to the 4000 RPM limiter - shutoff sequence. Note the condensation on the resonated tailpipe tips.

https://www.youtube.com/watch?v=AlhoW4BWgHs

Second video is a driving sequence. Up a short hill (off camera, around a loop, then back past the camera. Maybe a little lame but the last ~15 seconds gets the point across and I suspect is what you all were interested in. The muffler cans are kinda big and hung low in back. Rob used a Jones resonator, made the mufflers. Shoulda took pictures...

https://www.youtube.com/watch?v=0ClrUs29qS0

It will be most fun if you have computer speakers with subwoofer. The car is not *that* loud - in the videos you can hear the birds in the background (they come with the neighborhood...)

Other than that... gas mileage is up a little probably due to fresh plugs and a little less exhaust restriction combining to convince the ECM to run a little leaner. The old plugs looked normal - some tan-to-brown ash, and a little gap spread (gapped out at .061to .065; I installed them at .060 100000 miles ago). The Magnecor wires appear to be holding up fine after ~100,000 miles although I have not bothered looking at them in the dark to check for coronas because I am not having any misfiring or other problems.

Albertj

turtleman wrote:

albertj wrote:

OK, next question please - all other things being equal in a given exhaust system, what changes in tone happen when a longer resonator is swapped in for a shorter one (assuming same construction, straight thru pipe)?

Albertj

noisier, less deep sound

I witnessed almost exactly that scenario on a 4cyl ranger

You sure you don't have that backward?

Albertj

Glasspacks need length to work. If the scenario is having a 15" glasspack and then replacing it with a 30" glasspack, the longer glasspack will be quieter and probably deeper sounding. The 15 extra inches of glasspack is standing in for a piece of straightpipe here. More surface area for sound absorbtion - less sound.

If you mean a real resonator, then it's a different story. But I was thinking of something you might have put on your custom exhaust.

When I was researching components for the rest of my exhaust system(I've already installed headers and Magnaflow high flow cat 3" in/out)
I was considering using a Magnaflow 4" or 6" round stainless muffler with an 18" long body, 24" OAL and then continuing with 2 1/2" stainless pipe mandrel bent to a Y with 2 - 2 1/4" in/out Dynomax super turbo mufflers with a shell lenthg of 20". Then new stainless tips.
Anyone have any feedback on trying this system.

Rickw wrote:

When I was researching components for the rest of my exhaust system(I've already installed headers and Magnaflow high flow cat 3" in/out)
I was considering using a Magnaflow 4" or 6" round stainless muffler with an 18" long body, 24" OAL and then continuing with 2 1/2" stainless pipe mandrel bent to a Y with 2 - 2 1/4" in/out Dynomax super turbo mufflers with a shell lenthg of 20". Then new stainless tips.
Anyone have any feedback on trying this system.

As far as the parts go, that's not too far off from my last dual exit system. I used 2.5" dynomax superturbos and a 3" dynomax race bullet muffler/resonator, which I still use now. All of my pipe was 3" though. I bet with 2.5" pipe back from the cat and the slightly smaller rear/muffler piping, it would be notabley quieter, and more tolerable than what I had, which would be about perfect.

I suspect there will be some drone still but barely. I thought those superturbos made a really nice sound from idle all the way to the top. For me, switching from the 3" dp to the headers made a huge difference in sound, not really any difference in volume, but I wasn't sure I liked it. I don't think it matters what muffler you use as far as that goes though.

Have measured and there is enough room for the 6" round muffler / resonator.
Do you think I should use the 6" or 4" ????
Considering the same in / out dimensions what differences in sound would you expect from the 6 - 4".?

Rickw wrote:

When I was researching components for the rest of my exhaust system(I've already installed headers and Magnaflow high flow cat 3" in/out)
I was considering using a Magnaflow 4" or 6" round stainless muffler with an 18" long body, 24" OAL and then continuing with 2 1/2" stainless pipe mandrel bent to a Y with 2 - 2 1/4" in/out Dynomax super turbo mufflers with a shell length of 20". Then new stainless tips.
Anyone have any feedback on trying this system.

it's similar to what I got, but will have to measure the mufflers for you and comment on composition - Rob made them, which was interesting. Used a combination of fiberglass and stainless steel packing.

For those of you who have not replaced your cat yet - another difference in my system is I used a Walker cat - stainless steel and somewhat bigger than the Magnaflow cat - also about $50 more - it is a little smaller than the factory (AC) cat. Frankly, if you have a factory cat and the case has not softened up on you from outer shell corrosion, I would Definitely Keep It. I looked into my factory cat - it uses one of the Corning (I worked for Corning) thin-wall high performance substrates. IF my case had not gone soft I'd have kept it. As for the rest of you if your cat is not sooted up and it is not making the o2 sensor throw codes, I'd keep it and save the $200. What to do if you are not sure - get a replacement gasket (same as fits the Walker) then take after you cut off the exhaust pipe take a look thru the old cat with a strong light on the other side - like a 60W shop lite, or point it toward a sunny window. IF you can see light thru it when you look straight thru you're fine. IF not then consider putting on a Walker (also a high performance substrate to meet factory specs).

More on my system - for some reason Rob made the "Y" more like a "T" in my system. I did not remember to suggest that he start with an elbow and cut a notch out of it for the inlet. The T is 2 1/2"; he opened the 2 1/4" pipes to 2 1/2" to connect each muffler to the T.

As for your resonator Rick I'd use the 6", definitely. Unless you also want to rip out the interior and put Dynamat on the floorboards (which I will do when the Dynamat from Club RSX that I ordered arrives). The 4" won't drone much but the resonation off the floorboards and trunk might get to you on long trips. The resonation is not at the tone of the muffler, rather it is at an annoying harmonic. Gibson makes a truck resonator I'm thinking about swapping in when I find the time/$.

Finally oh by the way Rick, I'd consider getting the Hooker Maximum Flow mufflers if you can get them for your design.

Albertj

albertj wrote:

Finally oh by the way Rick, I'd consider getting the Hooker Maximum Flow mufflers if you can get them for your design. Albertj

I looked at the Gibson website and cannot seem to find a round muffler with the dimensions needed to use as an resonator.
The maximum size I measured while under the car was 28" long x 7" round
What P/N were you thinking of going with.?

The Gibson number I am thinking of is 420887 - it is a Race Superflow Muffler; Stainless Steel; 5 in. Case Dia.; 3 in. Inlet; 3 in. Outlet; L-20 in.;

This failing was planning to one of 2 other things:

Plan B is to get an OE stainless resonator from a wrecked Chevy Impala or GM and weld it in. It is similar size to the original Riv resonator. Undecided whether to get the resonator for the 6 or the 8 if I have to so this.

Plan C is to learn a whole heap more about resonator design and then spec one for Ron to build for me (the gold plated solution). I think the key would be to get the right dimensions for the center resonance chamber and build a muffler like the Gibson 789400S - it's a Helmholtz. Is not packed, rather just baffled/chambered. It is 8" not 7" diameter - but the design is interesting. . The muffler would have stock inlet/outlet pipe welded to louvered pipes and would be baffled about 1/3 2/3. The trick is to get the baffle plates the right distance apart for sound cancellation. I could pack the end chambers with a mix of fiberglass and stainless wool to control sound differently.

Albertj

#1BearsFan wrote:

When you finally get that exhaust built.... audio/video please!

Please tell me what you think of the sound.

First video is a cold start - revving to the 4000 RPM limiter - shutoff sequence. Note the condensation on the resonated tailpipe tips.

https://www.youtube.com/watch?v=AlhoW4BWgHs