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Old 02-10-2016, 09:44 PM   #1
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Default Flex section in MSM downpipe

I failed at car buying an bought an MSM. Since then, I've been trying to correct some small issues I have with both it's OEM configuration and aftermarket options.

That said, I don't yet feel like splurging for an ARtech downpipe, but would like to replace the OEM piece with something that has a flex section. I plan on running a cheapo Ebay pipe like 18psi did, which can be seen here:


My question is this: What's the best location for the flex pipe, or does it not really matter? It looks like I can fit a 4" in the rear straight section, or a 6" closer to the turbo outlet / front. What size flex pipe, and where?
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Flex section in MSM downpipe-80-p1020252_55e7ef5c76c43d043b78f3ac23df7d39297b4922.jpg  
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Old 02-10-2016, 10:01 PM   #2
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Why would you put one there when it's not made that way from the factory or on the brand name pipes?
Have you seen one cracked before?
I'ts fine
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Old 02-10-2016, 10:13 PM   #3
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Just because there's not one from the factory, doesn't mean it shouldn't be there or be improved (eg; **** ECU, **** bypass valve, **** TB inlet, rigid downpipe, etc) This motor twists under load just like every other longitudinally mounted motor with flexible motor mounts. FM doesn't use one, BEGI does, Abe does.

Additionally, for those who actually check, these cars have a tendency to constantly loosen the exhaust manifold nuts and back-out the studs. In my experience, this can be alleviated by a proper flex joint to relieve stress, in addition to Nordlocks and Resbond.

Anyways, back to that question...
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Old 02-11-2016, 12:55 AM   #4
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Quote:
Originally Posted by TheBigChill View Post
Just because there's not one from the factory, doesn't mean it shouldn't be there or be improved (eg; **** ECU, **** bypass valve, **** TB inlet, rigid downpipe, etc) This motor twists under load just like every other longitudinally mounted motor with flexible motor mounts. FM doesn't use one, BEGI does, Abe does.

Additionally, for those who actually check, these cars have a tendency to constantly loosen the exhaust manifold nuts and back-out the studs. In my experience, this can be alleviated by a proper flex joint to relieve stress, in addition to Nordlocks and Resbond.

Anyways, back to that question...
the studs back out from vibration of the engine, not the downpipe.
if anything I'd figure out how to brace it like the stocker was braced instead
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Old 02-11-2016, 09:43 AM   #5
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Whether the motor shakes, or the motor has side-to-side movement with accel / decel (which it does both) and the entire exhaust is rigid (which it is), this means that the weight & leverage of the manifold, turbo, downpipe and full exhaust is riding on those manifold studs & nuts. I'll consider a bracing option.

I appreciate the input, Vlad; I'm just looking for input specifically on where to mount the flex section, and the most appropriate size flex section.
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Old 02-11-2016, 09:49 AM   #6
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Quote:
Originally Posted by TheBigChill View Post
I appreciate the input, Vlad; I'm just looking for input specifically on where to mount the flex section, and the most appropriate size flex section.
Put the flex section in the bottom half near the flange for the mid pipe. Use whatever diameter pipe you have there, and one that is 6" long.
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Old 02-11-2016, 10:37 AM   #7
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Quote:
Originally Posted by TheBigChill View Post
Whether the motor shakes, or the motor has side-to-side movement with accel / decel (which it does both) and the entire exhaust is rigid (which it is), this means that the weight & leverage of the manifold, turbo, downpipe and full exhaust is riding on those manifold studs & nuts. I'll consider a bracing option.

I appreciate the input, Vlad; I'm just looking for input specifically on where to mount the flex section, and the most appropriate size flex section.
Couldn't be more spot on.
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Old 02-11-2016, 10:51 AM   #8
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Mount it towards the rear of the downpipe. I just want you to know it's pointless, and I want you to know why.

The reason I keep telling you about the brace is because while the MSM is built with performance compromises, it certainly doesn't have very many reliability compromises, and if left unmodified and unabused, they run for hundreds of thousands of miles, without cracking the downpipe or anything else.

There are TWO VERY important braces that restrict what you're saying is happening, from happening:
1) the OEM brace from the bottom of the turbo to the block.
2) the OEM brace from the oem dp to the trans tunnel

Both of those take all of that stress from the exhaust and not allow it to flex the turbo or the manifold.

You can reject my factual inputs, that's fine, as long as you understand what I'm saying to you.

Vibration from the lumpy BP that vibrates like crazy is not the same as back/forth movement from accel/decal and fatigue from the exhaust resistance.
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Old 02-11-2016, 01:35 PM   #9
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Quote:
Originally Posted by 18psi View Post
Mount it towards the rear of the downpipe. I just want you to know it's pointless, and I want you to know why.

The reason I keep telling you about the brace is because while the MSM is built with performance compromises, it certainly doesn't have very many reliability compromises, and if left unmodified and unabused, they run for hundreds of thousands of miles, without cracking the downpipe or anything else.

There are TWO VERY important braces that restrict what you're saying is happening, from happening:
1) the OEM brace from the bottom of the turbo to the block.
2) the OEM brace from the oem dp to the trans tunnel

Both of those take all of that stress from the exhaust and not allow it to flex the turbo or the manifold.

You can reject my factual inputs, that's fine, as long as you understand what I'm saying to you.

Vibration from the lumpy BP that vibrates like crazy is not the same as back/forth movement from accel/decal and fatigue from the exhaust resistance.

I'm not dismissing everything you say. You're right about the downpipe-to trans brace; it offers some relief, but it's inferior, gone, and staying gone. I came here for very simple exhaust fabrication advice; nothing more. I've never built my own exhaust, but would like to believe that my engineering education and experience isn't completely useless when approaching such a basic concept. I realize that around here there's direct link to one's assumed intelligence and whether or not they have a build thread with a quirky name.


I will however look at both options: bracing and/or a flex section. But in the meanwhile, I won't ever be convinced that a flex-pipe is useless in this application; I know better than that, as do the people who build these aftermarket exhaust systems
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Old 02-11-2016, 01:45 PM   #10
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Quote:
Originally Posted by TheBigChill View Post
I'm not dismissing everything you say. You're right about the downpipe-to trans brace; it offers some relief, but it's inferior, gone, and staying gone. I came here for very simple exhaust fabrication advice; nothing more. I've never built my own exhaust, but would like to believe that my engineering education and experience isn't completely useless when approaching such a basic concept. I realize that around here there's direct link to one's assumed intelligence and whether or not they have a build thread with a quirky name.


I will however look at both options: bracing and/or a flex section. But in the meanwhile, I won't ever be convinced that a flex-pipe is useless in this application; I know better than that, as do the people who build these aftermarket exhaust systems

Good luck with all your projects, I'll stay out of your threads.
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Old 02-11-2016, 02:04 PM   #11
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Right in the feels! J/K. I simply disagree with the idea that a flex is pointless.

In all seriousness, I welcome anyone's input, but I asked a straight question and was looking for an equally straight answer. It's like coming here and asking about the spring rates on FM Stage 1 suspension, and instead you get "Buy Xidas".

I'm still looking at a brace option, but originally shied away due to FM's design constantly breaking.
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Old 02-11-2016, 02:13 PM   #12
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hahaha ok I'll give you the xidas comment, that always makes me laugh as well.

Put it towards the rear past the o2 bung
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Old 02-11-2016, 02:23 PM   #13
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Yeah I don't think there is a "correct" place for the flex pipe. Put it where you can easily fit it and you should be good.
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Old 02-11-2016, 04:43 PM   #14
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Right on. Thanks guys.


Except for 18psi. You hurt me; you hurt me bad.
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