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Discussion Starter · #1 · (Edited)
I've been trying to find a more-or-less comprehensive listing as to which exhausts utilize the "donut" gasket, and thus will work with a stock (or in my case Cobb) downpipe. There is a thread on NASIOC which talks about type 1 and 2 DP's and CB's, but no list I can find. Please help with additions and corrections. Obviously, one type can in some cases be adapted to another. I think I know which category some not yet listed fall into, but I want 100% confirmation.

So....

Downpipes Using Donut Gasket:
Stock
Cobb Street/Race
Bosal

Downpipes Using 3" Flange:
Helix
Turbo XS
Maddad V2 (Available with Donut Gasket)
Invidia
APS (3" or greater)

Catback Systems Using Donut Gasket:
Stock Catback
Cobb Catback
Borla Hush/XR1 (3" Adapter Available)
SPT
BOSAL
Blitz Nur Spec R/Touring
Greddy EVO2/SP2
Espiler
RSR Exmag

Catback Systems Using 3" Flange
HKS Hi Power
Helix
Turbo XS
Invidia G200
APS (3" or greater)
Megan Racing

Catback Systems Using 3" Flange w/ Flex Section
Stromung (Donut Version Available)
Maddad Whisper (Donut Version Available)

Any others that people know for sure one way or another??????
Perrin?
Tanabe?
Ultimate Racing?
DC Sports?
5 Zigen?
Apexi?
 

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Discussion Starter · #3 ·
Thanks! Keep 'em coming!
 

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Stromung 3" Catbacks are available with the donut style flange or 3" with flex section(no donut). You might consider specifying which of the 3"(no donut) systems have flex sections. It is a thoughtful/desirable addition to a 3" catback(without donut gakset)

Rich
 

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Discussion Starter · #7 ·
Flex Section category added!
 

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Discussion Starter · #8 ·
Is there any other useful information people would like to see? I'd like to make this thread useful to everyone.
 

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Ok, I feel clueless here... what's a 'donut' gasket?

All I know is that I have a Stromung cat back that bolted up to my OEM cats.
 

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Discussion Starter · #10 · (Edited)
The "donut" gasket is a 2.5" gasket utilized by the stock exhaust to connect the mid and intermediate pipes (the midpipe is typically included as part of an aftermarket downpipe, unless the DP is a "shorty"). Some aftermarket downpipes/midpipes also use the stock donut gasket (IE Cobb), and are thus most easily compatible with the stock catback, or with catback systems designed to link seemlessly with the stock downpipe. Other aftermarket downpipes/midpipes have a full 3" flange to connect to catback systems that have a matching flange. The purpose of this thread is to identify which catback systems fall into either category, so that people will be able to tell easily how compatable a combination of aftermarket parts will be. *Note that the donut gasket is the "taper" commonly referred to in regards to our exhaust. The extent to which this is a drawback to performance at a given HP level is beyond the scope of this thread.
 

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Thanks! I'm glad I asked before purchasing a downpipe that wouldn't work... I guess I should look around to see if I can purchase Stromung's mid pipe w/flex section separate from the axle-back.
 

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Discussion Starter · #12 · (Edited)

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ender18d said:
I believe Daddysscp.com carries this product.
I just closed that page... :lol: they only had the donut style listed, but should I ever need to change it I'll get in touch with them.
 

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Discussion Starter · #14 ·
Bump... Can anyone fill in any more unknowns?
 

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Discussion Starter · #15 ·
Bump for some more help please!
 

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I had a Perrin twin tube catback mated to my stock DP for a few days. It fit.
 
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