I just bought myself a welder and my plan is to build a 3" turbo exhaust system from the downpipe to the muffler. The problem is that the only thng i can find was a t3 downpipe exhaust flange with a 2.5 in hole for the pipe. Would i be able to put a 3in pipe on that kind of flange with a 2.5 in opening. It's the 5 bolt flange for the side of a t3 turbo. I'm running a .63/.60 turbo and i built a Z6 from cam to forged rods for high boost. I wanted to create a bigger exhaust for the turbo.

 

just bore the hole out to 3"

 

yes you can weld a 3" to that 2.5" dp flange.
you could also just find a 3" 5-bolt dp flange. i think turbo-performance.com has them and i've seen them on ebay.
anyone have some links?

 

Mike @ LSDMotorsports carries them pm him

 

When I did mine i used a 2.5" to a 3" Exhuast Adaptor. One of the tappered pipe reducer things. Just cut it to be as long as the reduction and it worked fine. It was for a 14b turbo. Couldn't fit the pipe directly to it otherwise the bolts wouldn't go in.

 

I think I have a couple. They are 5 bolt but there is more than one style. SS laser cut but one or two of the holes didn't cut cleanly and had to be drilled.
$17 shipped to anywhere in the lower 48
Email me at morganf1@aol.com for pics

 

if your talkin about teh waste gate flapper housing then bore it out, go from 2.5-3in, or by a differetn housing i.e lotus esprit

 

i don't think it will make a difference weather the hole be 3" or 2.5 because the hole for the exhaust wheel probably isn't more then 2.5"

 

Unless the turbo outlet is larger then 2.5 inchs otherwise i would just use your 2.5 flange and weld a 3' pipe on it