3" Cat Back DIY (lots of pictures now)
05-12-2010, 02:05 PM
#34
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Just cut out the cat with cutting wheel and then clamp/weld in a piece of 3" pipe from parts store. Done and done.
30 min--6$ = 2-3psi regain, 200-500 rpm spool.....flow+psi gain about 20-40hp
05-12-2010, 06:33 PM
#35
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I'm finally getting around to doing this now.. the borla and pipe bends have been sitting in my basement for about a year now! Picked up a fabspeed 3" cat bypass pipe and tial 38mm to go with it (was holding off on the exhaust until I could afford these). Also found a stainless T04 discharge flange which appears to be the bolt pattern I need but with a 3" opening, so I'll use that to connect the cat-back to the testpipe. Now I just need to pick up some shielding gas for the MIG and I'll be good to go. 
05-13-2010, 10:12 PM
#37
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I am planning to build a cat back system for my newly acquired 87 951. I found the 45deg 409 stainless pipes from a vendor on ebay for the old $22 price! I bought a pair a few weeks ago.
05-13-2010, 10:14 PM
#38
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I'm finally getting around to doing this now.. the borla and pipe bends have been sitting in my basement for about a year now! Picked up a fabspeed 3" cat bypass pipe and tial 38mm to go with it (was holding off on the exhaust until I could afford these). Also found a stainless T04 discharge flange which appears to be the bolt pattern I need but with a 3" opening, so I'll use that to connect the cat-back to the testpipe. Now I just need to pick up some shielding gas for the MIG and I'll be good to go.
05-14-2010, 07:04 PM
#39
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Here's the one I bought:
http://cgi.ebay.com/ebaymotors/ws/eB...m=200468944759
Unfortunately the bolt pattern does not match up after all. What I'm going to do is just rotate it 45 degrees, trace the copper gasket on there and drill new holes, then trim the edges square. The original holes will be cut off basically. It's a pain, but at least the 3" hole is already cut.
http://cgi.ebay.com/ebaymotors/ws/eB...m=200468944759
Unfortunately the bolt pattern does not match up after all. What I'm going to do is just rotate it 45 degrees, trace the copper gasket on there and drill new holes, then trim the edges square. The original holes will be cut off basically. It's a pain, but at least the 3" hole is already cut.
05-15-2010, 08:37 PM
#41
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05-19-2010, 07:53 PM
#42
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Well I finished up my 3" exhaust this past weekend, big thanks for the diy info. Only thing I changed was the muffler to a Borla XR-1. With the SFR cat bypass I have to say this thing is loud as ****!!! Under boost it is mean sounding, but just crusing around I was worried what my neighbors were thinking. Has a pretty throaty idle as well. I'm probably going to add a pre-muffler or something where the cat was to make it a little more civilized. Luckily I'll never have to pass smog in VA again since it's over the 25yr limit now.
