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UP: Flex vs. Solid?


ogradnis

Which type of UP would you rather install/have?  

102 members have voted

  1. 1. Which type of UP would you rather install/have?

    • UP w/ flex section
    • Solid UP
    • Stay stock, stay happy
    • What's an UP?


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I was carefully looking at my stock UP pipe yesterday and there is no flex section what-so-ever.

 

Take a look at the post right above yours to see the stock unit with heatshield removed (#50). Did you buy your car new? Maybe it's aftermarket?

My VB Garage... Pumping the air back into despair
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  • 1 month later...

Anyone know what the inside diameter is on this APS UP?

 

Some flex uppipes will have a liner inside it. The liner is only welded on one side. It's to provide a smoother air flow. That doesn't mean it's not a flex.

 

The APS is like that.

 

http://www.finelineimports.net/images/APS_Turbo_Up_Pipe3.jpg

05 STI CGM~520whp/463wtq...more to come!

08 STI Aspen White/Gold BBS~305whp/365wtq:D

Both tuned by Scott Siegel!

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mickey - you must not use welding much in your current job. The weld you describe on the Perrin pipe is a fillet weld and is the strongest weld you can use. Crucial's pipe is fillet welded on the inside vs. the outside is all.

 

A butt weld is when two parrallel objects are butted against eachother and you weld along the seam - which as you state, is one of the worst forms of welds...mostly because of the poor penetration & depth of fusion it provides. Beveled edges are required to make a good weld in that case, but then it's no longer a butt weld, it's a bevel weld.

 

There are several other reasons why the Perrin weld might have failed though, probably contaminants or not enough heat input to get good fusion.

 

The strongest weld is a full penetration groove weld, not a fillet weld, since it fuses the full thickness of the base metal. Standard welding terminology refers to butt JOINTS, which can be welded many ways. A fillet weld all around is the usual way to connect a pipe to a flange, it is a balanced connection and normally should not fail. I have also spec'd full pen groove welds all around though. Sometimes it is possible to OVER weld, leaving residual stresses that can cause a crack to start. That can be taken care of by stress relieving (heat treatment) after fabrication.

I am a structural engineer and spec welds routinely. That being said, the stuff I design does not need to take these temperatures.

 

I am also quite interested in finding out what the best up pipe is...flex seems to make sense to me, but what about the flow?

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We have been debating the fact that the stock UP has a flex. Yes I see the area under the heatshield, but if you look inside the pipe in that area it is a solid tube. Am I missing something?

 

Look closely at the cut-away images posted in this thread. There is indeed a solid pipe inside there, but it is surrounded with a flex section.

My VB Garage... Pumping the air back into despair
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From the APS web-site...

"With an innovative internal 321 stainless steel Endurance Flow Tube, the external Double Wall 321 Stainless Steel flex is insulated from high exhaust gas temperature to ensure total durability - whilst providing a stress free coupling between the exhaust manifold and turbocharger.

 

Precision TIG welded into the entry flange, the smooth internal profiled Endurance Flow Tube also enhances exhaust gas flow for even greater horsepower and throttle response - especially when compared with up-pipes using a traditional flex coupling."

My VB Garage... Pumping the air back into despair
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I guess no one knows the inside diameter of the APS pipe. I cant even get APS to respond in an email.:confused:

05 STI CGM~520whp/463wtq...more to come!

08 STI Aspen White/Gold BBS~305whp/365wtq:D

Both tuned by Scott Siegel!

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other pics gone... here you go. APS calls it the "internal stainless steel endurance tube"

 

 

After some examination I have figuired it out. Technically, it does not "FLEX". It is a "telescopic" type connection which allows the pipe's length to expand and contract with temp changes.

 

I have the solid Indiva pipe, I wonder what will crack first, the header pipe, up pipe, or the turbo flange??:eek:

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  • 2 weeks later...

With all the issues I have had with a fixed-UP, I would probably go flex next time... or replace this one with a flex, if it continues to give me leaks at the exhaust gaskets. I needed 2 gaskets to make up the distance between the UP and the manifold... and this was after loosening the turbo and trying to get it all together.

 

Still, maybe I am doing something wrong, but flex seems better in my case - whether it's my fault or not :p

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