Stock vs Aftermark Downpipes

deadlyrhythm · 12-16-2010, 04:13 PM

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

Bimmer This · 12-16-2010, 04:37 PM

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.

2kaccordocoupe · 12-16-2010, 04:44 PM

Quote:

Originally Posted by Bimmer This

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.

I think the OP has a valid question here...

So if the AM pipes have no give then are they not pulling and or pushing on components up and down stream?

onefastman · 12-16-2010, 04:52 PM

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.

cn555ic · 12-16-2010, 04:56 PM

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!

NiVeDh · 12-16-2010, 05:08 PM

Quote:

Originally Posted by onefastman

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.

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).

Forcefed3 · 12-16-2010, 05:10 PM

Quote:

Originally Posted by NiVeDh

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).

Yea, I am kind of surprised AR hasn't added mounting brackets yet.

Imperator · 12-16-2010, 05:20 PM

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.

vasillalov · 12-16-2010, 05:39 PM

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.

Bimmer This · 12-16-2010, 05:45 PM

Quote:

Originally Posted by gbreeE90

Yea, I am kind of surprised AR hasn't added mounting brackets yet.

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.

Mr. 5 · 12-16-2010, 05:52 PM

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.

BrianMN · 12-16-2010, 06:32 PM

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.

ar design · 12-16-2010, 08:36 PM

Quote:

Originally Posted by NiVeDh

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).

We have sold over 700 sets with ZERO weld failures. Definitively not needed.

onesuperboi · 12-16-2010, 09:02 PM

Quote:

Originally Posted by ar design

We have sold over 700 sets with ZERO weld failures. Definitively not needed.

That's the JB excuse (thousands of tunes and billions of miles with no failure).

Have you guys even thought about it?

Bimmer This · 12-16-2010, 10:09 PM

Quote:

Originally Posted by onesuperboi

That's the JB excuse (thousands of tunes and billions of miles with no failure).

Have you guys even thought about it?

That's like people blaming McDonalds for making them fat!

Tiago@VRSF · 12-16-2010, 10:48 PM

Quote:

Originally Posted by onesuperboi

That's the JB excuse (thousands of tunes and billions of miles with no failure).

Have you guys even thought about it?

Why would you even consider it if it's not needed. Yeah I love adding complexity & cost where it's unnecessary, seems like a great idea.

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.

onesuperboi · 12-16-2010, 11:52 PM

Quote:

Originally Posted by tvieira24

Why would you even consider it if it's not needed. Yeah I love adding complexity & cost where it's unnecessary, seems like a great idea.

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.

I was hoping for some better explanation, even if the reasons were because it would cost more or it's unnecessary.

Saying that there have been no failures... well, is kinda lame.

guidance · 12-17-2010, 11:46 AM

Quote:

Originally Posted by onesuperboi

That's the JB excuse (thousands of tunes and billions of miles with no failure).

Have you guys even thought about it?

Yes doctor, I concur. It’s a mild case of Burger-phobia.

Zaw · 12-17-2010, 12:48 PM

Quote:

Originally Posted by tvieira24

Why would you even consider it if it's not needed. Yeah I love adding complexity & cost where it's unnecessary, seems like a great idea.

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.

+1

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.

Presidio335xi · 12-17-2010, 01:34 PM

Quote:

Originally Posted by Bimmer This

Aftermarket companies doesn't use them because it most likely interfers with flow.

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.

Bimmer This · 12-17-2010, 02:07 PM

I have seen a lot of those expansion joints crack.

12-16-2010, 04:13 PM	#1
deadlyrhythm Second Lieutenant 49 Rep 238 Posts Drives: 2009 BMW 335i Join Date: Apr 2009 Location: Edmonton, Alberta iTrader: (0) Garage List 2013 BMW X5d [0.00] 2009 335i [0.00]	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 Attached Images
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12-16-2010, 04:37 PM	#2
Bimmer This Major General 103 Rep 6,473 Posts Drives: 2007 BMW 335i Join Date: Nov 2008 Location: Westminster iTrader: (3)	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, 04:52 PM	#4
onefastman Major General 163 Rep 5,689 Posts Drives: 2009 135i 2011 e92m dct Join Date: Sep 2009 Location: Earth iTrader: (15)	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. __________________ Legal Disclaimer: Anything I or anyone else says about my vehicle on this website(1addicts.com or any affiliated or nonaffiliated sites), pertaining to modifications, is only to gain acceptance from my/our peers, and does not actually represent anything actually existing on my car, and thus, cannot be held against me in any issues, i.e. warranty claims, that may arise.
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12-16-2010, 04:56 PM	#5
cn555ic 462 Rep 18,331 Posts Drives: 335i Join Date: Jun 2007 Location: US iTrader: (6)	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, 05:20 PM	#8
Imperator Major 57 Rep 1,175 Posts Drives: 2010 E92 335i Join Date: Mar 2010 Location: Plano, Texas iTrader: (8)	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.
	Appreciate 0 Quote

12-16-2010, 05:39 PM	#9
vasillalov Mad Linux Guru On The Loose 1197 Rep 5,455 Posts Drives: 2008 335i Sedan, 2023 M3 Join Date: Aug 2009 Location: Chicago, IL iTrader: (5) Garage List 2023 BMW M3 [0.00] 2008 335i E90 [8.00]	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. __________________
	Appreciate 0 Quote

12-16-2010, 05:52 PM	#11
Mr. 5 Modder Raider 802 Rep 8,633 Posts Drives: M3 Join Date: Apr 2007 Location: Surf City, HB iTrader: (31) Garage List 2007 e90 335i [8.00]	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. __________________ e36 M3 Coupe, e36 325i Sedan e90 335i--SOLD Best 60-130-------------9.15 Seconds------------------WWW.MR5RACING.COM
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12-16-2010, 06:32 PM	#12
BrianMN Banned 117 Rep 2,428 Posts Drives: 4 Door Family Sedan Join Date: Sep 2009 Location: Minneapolis iTrader: (7)	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. Attached Images
	Appreciate 0 Quote

12-17-2010, 02:07 PM	#21
Bimmer This Major General 103 Rep 6,473 Posts Drives: 2007 BMW 335i Join Date: Nov 2008 Location: Westminster iTrader: (3)	I have seen a lot of those expansion joints crack.
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