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Thread: Another muffler exhaust question.

  1. #21
    Delorean Guru
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    Your rusting can also be due to the fact that Chinese S/S is prone to rusting. Overheating good S/S will just warp it, not make it rust. Popping and glowing in the exhaust is not due to being over lean, you are putting too MUCH fuel into the exhaust and it is burning in it getting it too hot or exploding (popping). If the popping gets too much you can actually blow the pipes apart. That's why you have decel valves on the throttle plates, to allow more air to get in if you slam the plates shut at high revs. The additional air leans the mixture to prevent the popping.
    David Teitelbaum

  2. #22
    EFI'd dn010's Avatar
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    Quote Originally Posted by David T View Post
    Your rusting can also be due to the fact that Chinese S/S is prone to rusting. Overheating good S/S will just warp it, not make it rust.

    My UK stainless exhaust system rusted over after many years, I also drove many of these years on salted roads in the winter so I'm not sure if that has anything to do with it. I was pissed my $$$$ exhaust system ended up looking like this so I contacted the company about it. The company assured me that it was built using 304 grade stainless and the appearance was 'normal' for it's age. They wouldn't budge on this determination and me being in the US, was unable to do anything further about it except buy a new exhaust system. As far as catalytic converters, I bought DPIs spec exhaust and wish I would have gotten it with the converters instead of straight pipes, I'm so tired of smelling like exhaust when I am done driving the D.

    Last edited by dn010; 02-12-2019 at 12:03 PM.
    -----Dan B.

  3. #23
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    The popping was happening with an AFR in the 18:1 to 22:1 (possibly higher; the wideband O2 sensor only goes to 22:1) range, if I remember correctly. The sound wasn't terribly easy to hear, though.

    I had also assumed that too much fuel would cause the exhaust to glow, but back when my valve timing was messed up in August or so the AFR readings were way up over the 22:1 range.

    Basically, my assumption was that the gas wasn't burning in the engine due to all the extra air and was instead making it to the exhaust where it burned instead. However, I really have no idea what I'm talking about.


    As for the stainless steel pipes, yeah, that makes sense. The very short pipe with the flange to the headers is steel and I expected that to rust, but the Magnaflow cats and the other pipes (made by Vibrant) are stainless. I have no idea where the metal came from. The muffler looks good, though, as do the tips and the clamps themselves. The clamp hardware is aluminized steel.

    -- Joe

  4. #24
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    Quote Originally Posted by dn010 View Post
    My UK stainless exhaust system rusted over after many years, I also drove may years on salted roads in the winter so I'm not sure if that has anything to do with it. I was pissed my $$$$ exhaust system ended up looking like this so I contacted the company about it. The company assured me that it was built using 304 grade stainless and the appearance was 'normal' for it's age. They wouldn't budge on this determination and me being in the US, was unable to do anything further about it except buy a new exhaust system. As far as catalytic converters, I bought DPIs spec exhaust and wish I would have gotten it with the converters instead of straight pipes, I'm so tired of smelling like exhaust when I am done driving the D.
    My mechanic friend saw my exhaust and felt that even though it's rusted that it would last until "the next owner", and he knows I have no intention of selling it.

    The other good news about my rust is that my exhaust isn't terribly expensive. There's under $200 in pipes, under $100 in clamps and $140 for the muffler. The cats were $125 each, but only because I decided to be all local code compliant and get 50-state CARB cats instead of the cheap ones. There's another $50 in misc parts here (hangers, flanges, etc), and $50 in tail pipes. The DPI headers cost as much as the entire rest of the exhaust, but those have to be built specifically for the 2.8L/3.0L engine, so that's to be expected. They also seem to be holding up very well, and I doubt I'll need to replace them anytime soon.

    I'm not actually sure if the pipes and cats are 304 or 309 stainless (apparently 309 will show rust, but is still more resistant than steel); the JEGS and Summit Racing sites don't seem to say.

    I should probably provide a link to my site where I discussion building the exhaust (and pictures of when it was nice and shiny): http://www.tmproductions.com/repairs...ing-an-exhaust. Note that I currently don't have the silencers in the pipes between the cats and muffler, as I took them out when diagnosing the glowing cats and pipes; instead, I have silencers without stainless steel wool packing in the pipes leading out of the muffler to the tailpipes

    -- Joe

  5. #25
    Owner since 2007 Farrar's Avatar
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    Quote Originally Posted by jangell View Post
    The Car Chemistry inserts might help with the drone. It seemed to help with mine, which was at about the same RPMs. JEGS has them for $57 each for the 2.5" with 3 discs (more discs means more silencing). You'll likely want a bench grinder handy so you can sand off the paint around the edges of the discs and a bit of the metal so that they'll actually fit in your pipes. You then rivet them in place (I used a magnet to find the discs), or run a bolt or wire through the pipe so they don't shoot out the back. While the CC guys say to install them before the mufflers but after the cats, you can install them after the mufflers as well. They just work best with hotter engine gases, but our exhaust is so short that there really isn't much of a run for them to cool down.
    Thanks for that link! I guess in my case they would go ... in the tips? #2613's exhaust currently has tips made from 2-1/8" I.D. stainless steel tube, what I call the "McMaster-Carr specialty tips". Before the engine swap I had resonator tips clamped on to the mufflers, but I installed them just before the 2.8L died so I never heard them. Bill just handed them back to me in a box. I don't think he even bothered with them. Or maybe he listened to them and decided they sounded awful. LOL My 2.25" in/out Borla exhaust is "throaty" and I do like the sound. It's not particularly loud, but it's not particularly quiet, either. (I made a video of it using my field recording kit for the best audio I could muster; it's on YouTube if you care to listen.) And of course I live in an area where there are no emissions requirements for antique vehicles.

    Anyway, sorry for derailing this thread! But I am interested to see where you go next with your exhaust.
    3.0L, automatic, carbureted

  6. #26
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    On the subject of rusting stainless steel, I had a grill (made by a reputable manufacturer) and it rusted so much it turned brown. The story was they got a shipment of S/S and it turned out to be from Asia. It was supposed to be of good quality but it was not tested. It is a very insidious thing, having companies and countries counterfeit and misrepresent products. It can get purchased by other companies that expect and demand quality and when it turns out to be less than advertised, the products made from it suffer. Anyway Chinese S/S is not up to the standards it is expected to meet. The metallurgy is inferior and the properties of the metal do not conform to world standards. It doesn't matter what they say it is because it isn't. The quality control is non-existant. What do you expect, they make stuff out of the recycled garbage they buy from all over the world. About all you can say is that it is cheap. There is a good reason for that, it is junk.
    David Teitelbaum

  7. #27
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    Quote Originally Posted by Farrar View Post
    Thanks for that link! I guess in my case they would go ... in the tips? #2613's exhaust currently has tips made from 2-1/8" I.D. stainless steel tube, what I call the "McMaster-Carr specialty tips". Before the engine swap I had resonator tips clamped on to the mufflers, but I installed them just before the 2.8L died so I never heard them. Bill just handed them back to me in a box. I don't think he even bothered with them. Or maybe he listened to them and decided they sounded awful. LOL My 2.25" in/out Borla exhaust is "throaty" and I do like the sound. It's not particularly loud, but it's not particularly quiet, either. (I made a video of it using my field recording kit for the best audio I could muster; it's on YouTube if you care to listen.) And of course I live in an area where there are no emissions requirements for antique vehicles.

    Anyway, sorry for derailing this thread! But I am interested to see where you go next with your exhaust.
    I think I already derailed it by going into detail about my exhaust.

    You can find some docs from Car Chemistry here. That includes installation instructions, which mostly boils down to which way they go in the pipes and what ends to optionally put the caps on.

    You could put the inserts either before the muffler or in the tail pipes in your setup, assuming you have enough length to do so. It could extend into the muffler a little without being a problem, I imagine. You can cut off part of the long end if you need to, too.

    This is one of the silencers stuck into the end of one of my pipes, with one of the caps (badly) welded on. I didn't grind off quite enough of the paint and edge metal on the discs, so I had to seat it with a rubber mallet and I still couldn't get it in as far as I would have liked, but it works fine.

    IMG_0678.jpg

    I don't know if this will help with your drone, but for $120 or so it's not too expensive to try, and shouldn't take long to install if your exhaust comes apart easily enough.

    -- Joe

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