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Stock vs Aftermark Downpipes - No expansion joints?
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12-16-2010, 03:13 PM | #1 |
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Stock vs Aftermark Downpipes - No expansion joints?
Curious, why don't aftermarket company's downpipes have the expansion joints that the stock ones do? Expansion joints aren't cheap and BMW doesn't hand sh*t out for free...
Picture: Inside downpipes are stock, outside are aftermarket |
12-16-2010, 03:37 PM | #2 |
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I'm pretty sure that the expansion joints are there to help with engine virbation and flex. Aftermarket companies doesn't use them because it most likely interfers with flow.
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12-16-2010, 03:44 PM | #3 | |
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So if the AM pipes have no give then are they not pulling and or pushing on components up and down stream? |
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12-16-2010, 03:52 PM | #4 |
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If AR doesnt use them then I wouldnt worry.
Supersprint does but they are over $2,000 and only 2.5" Get a set of AR, BB, AA, or MS depending on your pocket book and brand loyalty. All are good choices.
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12-16-2010, 03:56 PM | #5 |
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Being that the dps out there don't have this flex joint and there are no reported issues of not having it, you should feel confident as many members have logged enough miles with these downpours. The only one that I think has this flex joint is made by supersprint and the price is over 2000!!! Lol. That's just plain insane in the membrane!
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12-16-2010, 04:08 PM | #6 | |
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Although I love AR pipes and chose them (will be installing them soon), I would feel a lot better if they used expansion joints and had the support brackets (like the new AA DPs). |
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12-16-2010, 04:10 PM | #7 |
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12-16-2010, 04:20 PM | #8 |
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Aren't both mid-pipes suspended by a hanger somewhat close to the flanges where they interface with the downpipes? I realize that the lack of mounting brackets might put a bit more stress on the turbine housing, I doubt its significant enough unless the engine is subjected to abnormal flexing from a broken motor mount.
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12-16-2010, 04:39 PM | #9 |
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A flex joint in the downpipes is a great thing to have because:
* It helps absorb some of the tension on the turbo flange generated by the engine flexing in the engine bay * It helps absorb some of the vibrations. A straight pipe will simply transmit those vibrations to the exhaust. * It helps with adjusting the midpipes and other exhaust components. I could only speculate that the reason why no vendor is including these as part of their downpipes is added cost. That being said, I've not had any issues with my AR downpipes, nor have I heard of anyone else having issues either.
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12-16-2010, 04:45 PM | #10 |
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But AR downpipes weigh half as much as the stock downpipes. No mounted bracket is needed. If you look at the stock DP's, they are really heavy toward the cat therefore they use mounts to support the weight.
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12-16-2010, 04:52 PM | #11 |
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There's no need. There's so much movement in the rest of the exhaust system. Also, once you delete the cats that part doesn't even get as hot as with the stock cats so there's less of a reason for expansion joints.
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12-16-2010, 05:32 PM | #12 |
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Have you guys tried "Flexing" the actual joint? It is definitely no "Flex Joint", unless their maluability changes when they get 800* or hotter. They are only expansion joints for changes in temp, to contract or stretch when the engine (and exhaust) get warm as a couple others said. Is it necessary? Many of us wouldn't care to have them. These joints don't provide "cushion" by flexing when the engine is under load, dampen vibrations, or resist push/pull on the turbine outlets.
So, if you want the downpipes to have a little 'give' in them to keep stress/tension off of the exhaust and turbo flanges, you'll have to install what is pictured below...the OEM type expansion joints don't achieve that. |
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12-16-2010, 07:36 PM | #13 |
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12-16-2010, 08:02 PM | #14 |
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12-16-2010, 09:09 PM | #15 |
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12-16-2010, 09:48 PM | #16 | |
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They haven't added one because it's not necessary. Period. Adding them means they have to worry about extra tolerances while fabbing them up & makes installation more difficult overall. |
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12-16-2010, 10:52 PM | #17 | |
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Saying that there have been no failures... well, is kinda lame. |
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12-17-2010, 10:46 AM | #18 |
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12-17-2010, 11:48 AM | #19 | |
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I am sure BMW is not paying all the engineers to think of a bunch of unnecessary BS to install on the car. Than again, they are making the car for everyone. I'm sure the guys that get these DP's don't mind a little extra vibration. The real question OP has is what's going to happens in the long run. As for me, when ever I get an aftermarket mod, I'm thinking it's great now but probably not good for the car in the long run. I'm just hoping it'll be ok. wishful thinking I'm sure. |
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12-17-2010, 12:34 PM | #20 |
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Not the case. If you look inside the OEM DPs they are completely smooth. It has to do with vibrations. But reality is that so many people have had aftermarket DPs with no problems....maybe after 75k or 100k there will be issues, but not many of us will have our cars for that long.
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