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Discussion Starter #1
Hey guys... New to the forum... loving it so far. Anyway... I figured i would start off my existence here with a possibly dumb question.

Ok... Perrin sells their down pipe as a two piece unit. Both of these contain catalytic converters. So, does that mean that this downpipe flows less than say, cobb's downpipe? Thanks for any answest guys...
 

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Hey I have been looking at exhaust for a while this is what I figured out.
Less cats the better. But I think it is easier to think of it between catted and cattless. I have read that there is 5hp or less difference Between the two. So to go from two cats to one... I would find it some where less than 5 hp. To me not a big deal as long as they are highflow cats. If you are looking at Perrin or Cobb the bigger difference is in the construction of the pipe. They are both great pipes, but I think this is the bigger difference

Perrin runs a divorced wastegate.


Where as Cobb runs a bell mouth


I have really not found any litature that states one method is better that the other. I like the single piece construction with one highflow cat of the Cobb pipe, but the idea behind the divorced pipe is the separation there is between the wastegate gases and exhaust gases, the smoother the overall exhaust flow sounds good to me too.

As you can tell I am still deciding... It is still early in the game, more pipes will come out...

Hopefully I did not just throw you for a loop. I guess I was being a little long winded ;D ;)
 

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I would go with the divorced, it give you better exhaust flow out of the turbo.
 

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Discussion Starter #5
Works for me ;D Besides, Perrins is prettier... So another question... With the spt exhaust being a 2.5 in. exhaust, would it become a restriction if the downpipe is 3" ? Just a question... I like the current price of $305 dollars, but honestly i think that i would not mind spending some extra money for a better total system...
 

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Works for me ;D Besides, Perrins is prettier... So another question... With the spt exhaust being a 2.5 in. exhaust, would it become a restriction if the downpipe is 3" ? Just a question... I like the current price of 5 dollars, but honestly i think that i would not mind spending some extra money for a better total system...
I think in your case go full system. 3" into a 2.5" is pointless.
 

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Better off getting all 3" Your car will love you more for it. ;D
 

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Discussion Starter #8
Well, i want my car to love me... Angry cars are no fun... Just new to the whole turbo thing... My last rides were a 91 E30 BMW w/ Ls2 Swap (lost in divorce) and an '03 Pheonix Yellow M3 (Creamed By Charleston Port Authority Truck running a red light) .... obviously im not the luckiest guy in the world... But this wrx is awesome so far... sorry for rambling... bored at work. lol
 

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I've also been looking at getting the Perrin DP, but I'm sort of confused on whether or not there's a difference between buying it in two parts or just the whole piece as one part? Anyone else notice that on the website? This is probably a stupid question, but one I don't mind asking, so I don't spend a ridiculous amount of money on the wrong thing, haha.
 

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Check out the Perrin'f from Fred Beans. They have a single unit with one cat. They had a stellar sale a while back. Pm them and see what kind of pricing they can get you.
 

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Perrin sells their downpipe in both a 2-piece and single piece option. Just go with the single piece downpipe. 2.5" to 3" will work, as I am using it, but if I could do it all over again I'd go full 3" turboback exhaust.
 

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The HP difference between a dual cat DP and single is truly about 3-7HP depending on the car. Our divorced wastegate helps to divert the wastegate exhaust gases away from the exhaust coming from the turbine. The less turbulence at the turbo outlet the better!!
 

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Perrin sells their downpipe in both a 2-piece and single piece option. Just go with the single piece downpipe. 2.5" to 3" will work, as I am using it, but if I could do it all over again I'd go full 3" turboback exhaust.
It's my understanding that they sell it in a two-piece because the stock DP is technically in two pieces, also. This way, people can replace one or both of these as they see fit. Some people just do the top piece ("shorty downpipe," no?) and call it a mild stage 2. I met a guy with an '05 LGT that did this, and as we all know, it's the same turbo/intercooler/downpipe architecture on our cars.
 

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If sticking with the SPT cat-back, I'd personally run the Cobb dp (it necks down to 2.5" ).

I plan to run the Perring one peice catted DP with Perrin cat-back.

That's just me.
 

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If sticking with the SPT cat-back, I'd personally run the Cobb dp (it necks down to 2.5" ).

I plan to run the Perring one peice catted DP with Perrin cat-back.

That's just me.
Thanks in advance for choosing PERRIN!

On the SPT Cat-Back, you can mate the PERRIN DP to it as well. The Divorced Wastegate is a benefit over the bellmouth (I stay away from the argument about that, but some reasonable research with "the Google" will give tons of good data) and as such makes the logical choice.

As always let me know if I can help further!
 

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I have to admit that while quite simply it sounds like the 2.5in Cat back would be restrictive, it isn't. I am running a DP with the stock exhaust and it really isn't that limiting. The full 3 inch exhausts are probably adding only a couple of HP. Bang for the buck, DP first, then add the CBE to get the last couple HP out of it.
 

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Looking into a Downpipe real soon. And I am getting a Perrin. Now I have stock exhaust will it mate perfectly? And if i wrapped it up, will it be more effective?
 

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Looking into a Downpipe real soon. And I am getting a Perrin. Now I have stock exhaust will it mate perfectly? And if i wrapped it up, will it be more effective?
Thanks! The DP will bolt directly up, no problem! You can wrap it if you choose. I don't have any dyno comparisons to tell you any HP gains.

Thanks again!
 
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