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1055 10-10-2012 04:20 PM

To all you turbo manifold gurus..
 
Im sick of the flex pipe in my one piece manifold/up pipe combo leaking. Aside fromthe minor heat expansion and slightly better fitment, does it serve a purpose? Whats to stop me from removing it and putting in a piece of pipe that doesnt leak?

AZP Installs 10-11-2012 10:43 AM

Nada. Go for it.

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fahr_side 10-11-2012 11:08 AM

Quote:

Originally Posted by 1055 (Post 4109364)
Im sick of the flex pipe in my one piece manifold/up pipe combo leaking.

Your engine / transmission mounts have obviously failed. Replace those and your stock up-pipe will last forever.

BAC5.2 10-11-2012 11:32 AM

Quote:

Originally Posted by 1055 (Post 4109364)
Im sick of the flex pipe in my one piece manifold/up pipe combo leaking. Aside fromthe minor heat expansion and slightly better fitment, does it serve a purpose? Whats to stop me from removing it and putting in a piece of pipe that doesnt leak?

1) There aren't ANY one-piece tubular header systems that don't leak. It's a "when", not an "if", with very few exceptions.

2) Does the flex serve a purpose? Absolutely. There isn't a "minor" amount of heat expansion, it's actually pretty substantial at high EGT's.

If you cut out the flex and weld in a piece of straight pipe, you will almost certainly crack your header. When the pipe hits 1500F, it going to expand radially and linearly. This is only exacerbated in thin-wall tubular headers. That growth must be mitigated somewhere. Slip joints in lower headers (and the flex in the OE cross pipe) handle this well (though like I said, slip joints are designed to leak unless extremely hot), and a flex in an uppipe help handle this. Eliminate those, and at best you'll get gasket leaks at flanges where they warp. At worst, you'll crack welds. Our headers are on the bottom of the car, in exactly the worst place for environmental exposure, so rapid temperature transitions are par for the course.

Your best option? Go back to a stock header/uppipe combo if the car isn't one run on the bleeding edge more often than not. If it IS a race car, or you think you HAVE to have headers, then replace your leaky flex with one of extremely high quality.

Be warned, though, that unless welded correctly, anything you do will very likely crack at the weld.

1055 10-11-2012 11:46 AM

Quote:

Originally Posted by fahr_side (Post 4110453)
Your engine / transmission mounts have obviously failed. Replace those and your stock up-pipe will last forever.

Brand new engine mounts. Trans mount was done recently. Manifold was purchased used and leaks. Thats why im inquiring.

1055 10-11-2012 11:46 AM

Thankyou azp.

BAC5.2 10-11-2012 01:34 PM

Lol, did you just want someone to tell you what you wanted to hear? Or did you want the right answer?

1055 10-11-2012 07:01 PM

And what is the right answer? Im looking to repair my leaking manifold. I bought it leaking, please.. do tell.


EDIT: for some reason your initial post bac is not showing up in tapatalk.. yet in the web browser it appears fine.

1055 10-11-2012 07:16 PM

Just read you're answer and thats what i was looking for. I didnt think t306 would expand that much. I also have never seen my EGT's go over 1100.. granted that is being monitored by the subaru ecu and not a third party unit.

I will be replacing it with one that doesnt suck. Welding it correctly is no issue. Will probably go with one with a large enough ID to slip over the pipe instead of ******* around with a butt joint.

fahr_side 10-11-2012 08:07 PM

Quote:

Originally Posted by 1055 (Post 4110514)
Brand new engine mounts. Trans mount was done recently. Manifold was purchased used and leaks. Thats why im inquiring.

Just wondering if you'd forgotten your statements in this thread.

BAC5.2 is right. You can cut the flex section out and weld a solid pipe in there, but that just redirects the force of expansion somewhere else. The header will then crack at the next weakest location, sooner or later. In your position I'd probably just get a better header. If I really, really liked the leaking header, I'd try welding a new flex section into the up-pipe and hope that holds for a while.

1055 10-11-2012 09:31 PM

Quote:

Originally Posted by fahr_side (Post 4111254)
Just wondering if you'd forgotten your statements in this thread.

BAC5.2 is right. You can cut the flex section out and weld a solid pipe in there, but that just redirects the force of expansion somewhere else. The header will then crack at the next weakest location, sooner or later. In your position I'd probably just get a better header. If I really, really liked the leaking header, I'd try welding a new flex section into the up-pipe and hope that holds for a while.

I'm well aware of what i said, and well aware of your mockery.

I'll be welding in a new flex pipe.

BAC5.2 10-11-2012 09:33 PM

Quote:

Originally Posted by 1055 (Post 4111163)
Just read you're answer and thats what i was looking for. I didnt think t306 would expand that much. I also have never seen my EGT's go over 1100.. granted that is being monitored by the subaru ecu and not a third party unit.

I will be replacing it with one that doesnt suck. Welding it correctly is no issue. Will probably go with one with a large enough ID to slip over the pipe instead of ******* around with a butt joint.

304, you mean. And yes, it expands quite a bit. I don't believe the stock EGT can read higher than 1100F, but someone like Fahr would know for sure.

If your peak EGT's really are 1100F, then your tune is leaving a LOT on the table.

If I were you, I'd probably go back to stock headers. Most street cars won't benefit from aftermarket headers until you reach pretty aggressive levels of power.

fahr_side 10-11-2012 11:11 PM

Quote:

Originally Posted by BAC5.2 (Post 4111351)
I don't believe the stock EGT can read higher than 1100F, but someone like Fahr would know for sure.

At this point I doubt the OP would believe my answer. ;)

Quote:

Originally Posted by BAC5.2 (Post 4111351)
If your peak EGT's really are 1100F, then your tune is leaving a LOT on the table.

I'm pretty comfortable going up to about 800*C or 1475*F. Some will go higher, some tune for lower temps for extra reliability.
Quote:

Originally Posted by BAC5.2 (Post 4111351)
If I were you, I'd probably go back to stock headers.

This.

1055 10-12-2012 05:44 AM

Quote:

Originally Posted by BAC5.2 (Post 4111351)
304, you mean. And yes, it expands quite a bit. I don't believe the stock EGT can read higher than 1100F, but someone like Fahr would know for sure.

If your peak EGT's really are 1100F, then your tune is leaving a LOT on the table.

If I were you, I'd probably go back to stock headers. Most street cars won't benefit from aftermarket headers until you reach pretty aggressive levels of power.

You are correct, 304. I wanted something drivable with a bit of spunk and great reliability. Mind you its an ej205. Going for a final retune in a couple weeks and we shall see how that changes everything. It wouldnt surprise me if the stock sensor maxed out there.

1055 10-12-2012 05:46 AM

Quote:

Originally Posted by fahr_side (Post 4111455)
At this point I doubt the OP would believe my answer. ;)


I'm pretty comfortable going up to about 800*C or 1475*F. Some will go higher, some tune for lower temps for extra reliability.

This.

Im pretty reasonable, give me logic and some believable factual evidence and ill be on board.

The reason i replaced the stock manifold was because it was rotted to shit. It was cheaper for me to go aftermarket then to find a good condition stock one. The car i picked up for my swap sat for two years exposed to new england elements.


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