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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 went with an Invidia solid uppipe. On of the cheaper upipes at $115 shipped. With thick FLAT flanges. Had it ceramic coated in/out along with my Invidia downpipe, Local ceramic coating place was $116 for both pipes with a 1 year warranty. Installed with new OEM gaskets for no leaks.

 

I think the Flex/solid debate has more to do with the quality of the install than the pipes themselves.:hide:

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I say you two are just lucky and can suck my balls! :D
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I bought the Indiva UP pipe. It is solid and I had no problem at all with the install. I considered getting a flex, but if it was of any real benefit Subie would have had it OE IMO.

I'm very happy with it, no leaks (11,000mi since install) and it was well constructed in fit and finish.

 

And no, I wont suck your balls!:lol:

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never had a problem with my Flow Solid UP (coated) with either my broken @ss borla headers or the stockers.

 

Loosen up at turbo side first, tighten and torque header to block and header to UP first, then finally do the turbo... at least that works for me.

 

 

Mike

SoCal Duck Hunters Club - Unit 52
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I considered getting a flex, but if it was of any real benefit Subie would have had it OE IMO.

 

What are you even doing on this forum if you think that Subaru puts chooses parts to install because they are the best available.:lol:

 

I guess you are bone stock and plan to stay that way then? Since when does Stg 2 = Stock?

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What are you even doing on this forum if you think that Subaru puts chooses parts to install because they are the best available.:lol:

 

I guess you are bone stock and plan to stay that way then? Since when does Stg 2 = Stock?

 

Whats with the flame dude? Did someone piss in your cornflakes this morning? I voted, listed what I had and stated why I went with a solid pipe. I never stated Subaru would use the best. :confused:

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Whats with the flame dude? Did someone piss in your cornflakes this morning? I voted, listed what I had and stated why I went with a solid pipe. I never stated Subaru would use the best. :confused:

 

As a matter of fact my cat is in heat and she did piss on my favorite belt yesterday; however, I apologize for the way that came across. I didn't intend to sound like so much of an asshole. I was just trying to pick on you a little.

 

In any case. I also did not know the stock UP had a flex section.

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As a matter of fact my cat is in heat and she did piss on my favorite belt yesterday; however, I apologize for the way that came across. I didn't intend to sound like so much of an asshole. I was just trying to pick on you a little.

 

In any case. I also did not know the stock UP had a flex section.

 

Absolutly no offense taken....we all have a "bad pill day" now and then.:icon_wink I had to keep looking back to see if I had said something rude . (which ocasionaly I do!)

 

I had to dig up my old UP pipe just to satisfy my curiosity about the flex.

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Spoke to Rich at Precision Tuning - he prefers the solid Perrin pipes. They install up-pipes all the time and see less leak issues with solid pipes like Perrin / Invidia than they do with flex pipes of lesser quality.

 

Apparently the flex units cost less to make as they require less exacting engineering tolerances.

My VB Garage... Pumping the air back into despair
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If you're going to get a solid uppipe, don't get the Perrin.

 

The Perrin is a butt weld. The pipe is butted against the flange and then welded. Any bending or flexing is taken by the fillet weld in tension. This might be fine for a downpipe or CBE, but the uppipe is very hot. The high temperatures will weaken the weld and the bending stresses will eventually cause it to crack. I have one on my workbench as a classic example. It failed sometime between 12,000 and 15,000 miles.

 

You can help this by coating the ID of the pipe. This will reduce the temperatures at the weld.

 

The better solution is to get a Cobb cast or Crucial. The Crucial is different because the pipe goes all the way through the flange. It is then spot welded on the outside to hold it in place and then a full weld on the inside. It is then fully coated.

 

20 years ago, in my college strain gage lab, the pipe weld on a flange was used as a classic example. We tested the difference in strain on the weld if we butt weld or insert the pipe into the flange. It was an order of magnitude difference in stresses on the weld.

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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.

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You are right that I don't do any welding in my current job.

 

However, this is almost the exact same configuration that we tested in college. In that case, we were checking the weld on a pole. My terminology is probably incorrect. The weld did not fail in our test. We strain gaged it and were measuring strain not failure.

 

The fillet weld may be strong, but the stresses are higher because of the configuration.

 

Here is a sketch of what I am talking about.

959753405_crucialweld.JPG.934b2fda6f5102b03b6d16445807cc2b.JPG

2133033953_perrinweld.JPG.0f280c16495c6d089126d6075cb23168.JPG

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Hmmm... the pictures on the Crucial website don't look exactly like your sketch. Close, though. Looks like Crucial does not stick the pipe quite all the way through the flange, but rather leaves it 1/4" short or so and welds there, inside the hole in the flange - probably to keep the weld away from the flat surface of the flange. The Corky Bell sketch describes it better than the pix. Same idea, I guess, and I agree that it's the superior technique.

Seek first to understand, then to be understood.

 

In other words: SEARCH before you post!

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