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Discussion Starter · #1 · (Edited)
I work for a major manufacturer of spiral wound gaskets for the petrochemical industry, whom also designs gaskets for the automotive industry. I consulted one of our engineers concerning the up-pipe issue, presented him with the facts and got a very intelligent answer from him. I originaly wanted to see if he could design a set of gaskets that would be superior to the factory's OE gaskets and resist leaking when used with solid uppipes. He analysed the entire situation and came up with a good, fundamental blanketed response. Before you read:

Caveats:
1. This is the result of an independant engineers analysis done in his spare time. The engineer is a PhD with over 15 years experience in the field, I would consider him to be an expert. However, this should be regarded as an opinion.

2. Please do not ask me for the company name. No, my company will not produce gaskets for individual sale, even for a group buy. This was to be a one-off solution as a favor to me. We produce gaskets that are not labeled (by us)and are sold to OEM's, like Kenworth, Volvo, etc.

3. This is not a "bash" on mfg's of solid pipes. Yes, you will have a person or two say "Dude, yer f'ed in the head, I put my uppipe in with Elmer's Glue and it hasen't leaked in 10,000 miles! AHAHAHAH LOL OWNED!!!!!!!" :rolleyes:


Here it is:

____________________________________________________

XXXXX,


After researching your challenge with the seal issue with the "up pipe" exhaust pipe system (at the flanges) on the USDM Subaru Imprezza WRX, I have made the following determinations on the nonflexible aftermarket designs versus the flexible units:

1. OE design is a flexible tube made of a mild steel. According to Fuji HE engineers this part is subject to vibration, tensional, compressive stresses and shearing stresses due to motor movement and vehicle shift, coupled with a thermal differential within 200C during normal operation. The stresses require flexion relief at this joint because a. the exhaust manifold is not a flexible abutment and b. turbo mount requires movement due to centrifugal oscillation cancellation of the turbo and movement of the exhaust system post turbo exit and c. engine tensional flex shift on its motor mounts can be rapid and requires 1/2 to 3/4 inch flexion at this joint.

2. The aftermarket parts that are not flexible will tend to flex at the flange-gasket abutment area due to the nature of the compressive pressure gasket's design. The gasket will become the most compliant joint in the structure subjecting it to high tensional and compressive stress. This will cause over compression at the flange abutments and eventual seal loss due to gasket over-compression and compaction; inside exhaust pressure and gas temperature will also be an antagonist to this premise. Also, aftermarket components manufactured from rolled 304 stainless tubing may tend to fail (stress fracture at seams) under these stresses; this material used in a solid, non-flexable pipe would not be suitable to the thermal variances under the application of an exhaust pipe at this location on this vehicle.

3. Doubling up on the gaskets and use of sealants essentially simulates a lower compliant joint and allows for flexion relief and thermal dynamics, but over time will result in a seal failure as noted above.

4. Design of a spiral wound gasket with a titanium inner ring, wound titanium + PTFE (or Thermiculite) and an outer compressive pad would provide sufficient heat tolerance but the issue comes back to flexion stress relief.

5. My research leads me to conclude that sealing a solid or high compliant pipe within these two flanges would be a high maintenance issue requiring replacement of the gasket at intervals.
 

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the assessment would lead one to grab an MRT up-pipe that has a braided flex joint in the middle.

Food for thought!

Thanks for getting the opinion from your buddy.

Andrew
 

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If he spelled "Impreza" right and wasn't REALLY BIASED towards his design, I'd believe him.

Let's face it people. We mod our cars. If we wanted OEM reliability, we'd use aLL OEM parts installed by um...the OEM!!!

Stop complaining. My Godspeed uppipe with FireSeal 2000 will hold much longer than I need it too. I'll have solid headers in before it fails.

-Jim
 

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Don't get me wrong, I'm not jumping on any band wagons - I am putting in a TurboXS up-pipe with new gaskets and goop next weekend and have little doubt that I will get it sealed satisfactorily.

There is never a black and white view of the world - there are compromises throughout in all designs -but titanium and kevlar and the like are expensive!! I am happy paying only ~$200 for an up pipe!!!

But Jim, give the guy a break - 15 years making/designing gaskets - you would be biased!!!(or crazy!!)
And engineers.....well.....we (yes I say we, because I am one too!!) always shoot for the most expensive and 100% solution when the 80% solution (solid up pipes for example) will actually meet the needs of 99.9999999% of applications!!!

No flame here intended!!

lotsa love the friendly Aussie in St Louis!!!
 

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Discussion Starter · #5 ·
Err, I didn't get a gasket made - I was suggested to use a flexible pipe. He said that basicly this pipe needs to act as a flex joint and putting in a solid joint transferrers the flex stress to the flanges. The gasket becomes the next weakest link in the chain. :eek:
 

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Sounds to me like Pace's solution (unbolting the turbo bracket to provide flex) has just been validated by this guys investigation into the problem.
 

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The Enemy said:
Sounds to me like Pace's solution (unbolting the turbo bracket to provide flex) has just been validated by this guys investigation into the problem.
Yes and I can't say enough about the FireSeal2000. Stuff is AMAZING.

-Jim
 

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There are thicker uppipe gaskets available now, I believe Irvine Subaru has them for $20/set or $13 each. They are twice as thick as the OEM gaskets. I saw a post over on i-club in the vendors forum.
 

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I have the MRT flex up pipe in my car. It has been in for 3000 miles and does not leak. The car sees red line at least twice a day. heat shields were reinstalled (less the one mounted on the side of the up pipe). New factory gaskets were used.
As the Master of pain's post described it this component sees a lot of stress. consider the thermal stresses alone. the different materials and coefficients of expassion.
For me the extra c note was money well spent.
I always keep OEM in mind when modding my car. As a fellow engineer I never redesign something that works well already. With that in mind- the offending portion of the up pipe's design was the catalytic converter. No need to mess with the flexability aspect.
Now before the flame throwers come out- I am 100% sure there are solutions other than the MRT flex design
 

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PlatinumWRX said:
If he spelled "Impreza" right and wasn't REALLY BIASED towards his design, I'd believe him.
Big Jim, what exactly is his design? I must have missed that part. Looks to me like he is simply suggesting that some sort of flexible pipe should be used to relieve stress on the flanges. He didn't even mention the MRT uppipe, which would seem to solve the problem without having to leave the turbo bracket unbolted.

Side note: As your post count swells, so does your head. It's obvious that no one will ever be as knowledgable as you, but you don't need to constantly rub it in. :rolleyes:
 

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Bask Oner said:


Big Jim, what exactly is his design? I must have missed that part. Looks to me like he is simply suggesting that some sort of flexible pipe should be used to relieve stress on the flanges. He didn't even mention the MRT uppipe, which would seem to solve the problem without having to leave the turbo bracket unbolted.
I believe Jim was referring to point #4. However, notice that he (not Jim) said the flexion stress problem would still exist, thus "his product" would not meet both requirements.
 

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WRXed said:
I believe Jim was referring to point #4. However, notice that he (not Jim) said the flexion stress problem would still exist, thus "his product" would not meet both requirements.
Yeah, my head is freaking huge. My helmet doesn't even fit.

There are atleast four ways to seal an uppipe. Most of them work too. I was in total agreement except for #4.

-Jim
 

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Bask Oner said:


Side note: As your post count swells, so does your head. It's obvious that no one will ever be as knowledgable as you, but you don't need to constantly rub it in. :rolleyes:
Man...why do you even feel the need to mention something like that? Happy family...happy family...happy family :D

peace
-Josh
 

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Or you could go with a OEM JDM STI Uppipe that is made by SUBARU that is almost GUARANTEED not to leak. Flanges are completely straight and there is no bung to leak out of either. It also looks like a stock cat-equipped Uppipe. Got mine. Installing it this weekend. Will have pictures and comments about it after this weekend. Here's a sneek peak.

Kurlee Daddee
(THE ORIGINAL)
 

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So bascially what he's saying is that the Subie engineers knew what they were doing when the put in a flexible pipe. Amazing. ;)
 
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