DIY 1G downpipe

[LordZed]

Hey guy's,
I'm toying with the idea of making my own downpipe. As far as flanges go, what size will bolt to my O2 housing? I'd like to run a 3" downpipe, but I'm not sure if it will bolt right up. Will I have to go 2.5 or can I go 3" making my own. Any good idea where to get flanges? I checked Summit and it seems they only have 2.5"

 

[wishihadatalon]

I believe it is a 2.5" flange from the o2 housing. Also I would check your local part stores or a local muffler shop. You would be surprised what they have in stock.

 

[the_skin_eater]

If you need a flange let me know. I can make up anything you want.
Id say go for 3"...Why not.

 

[LordZed]

If you need a flange let me know. I can make up anything you want.
Id say go for 3"...Why not.

The only reason I would not go for 3" is if it would not bolt right up to the stock O2. But thanks for the offer! So you think I can bold up a 3" flange right to the O2 huh? I'll go for it. Any one elso who has done this themselves post up some pointers or pic's please.

 

[nuclearpenguin]

I noticed today that punishment-racing also has that flange for sale on their site

 

[the_skin_eater]

As long as the flange is the same size it will bolt up. The only thing changing is the hole size....However, unless the o2 is 3", it will be a little useless.

Going from a small hole to a huge hole will work, but its kind of a waste...unless your upgrading that soon too, then might as well do it once.

 

[wishihadatalon]

fyi 2.5" o2 housings have flowed over 600whp. Just expand the pipe after the flange.

 

[Byrd]

I have a 2.75" flange on my DP then it goes to a 3" right after. Megan DP from ebay - I believe that's the biggest flange you can have while still being able to bolt right up

 

[xveganxcowboyx]

Check VFAQ for the DIY exhaust. A 3" pipe will work just fine with a stock style flange. You simply have to dimple the piping around the bolt holes to make sure you can get the nuts on the studs.

 

[LordZed]

Thanks for the advice everyone. I plan on porting the O2 while I'm at it. I'm going for a 3" and just work around the bolt's as suggested.

 

[RayPeters]

Check VFAQ for the DIY exhaust. A 3" pipe will work just fine with a stock style flange. You simply have to dimple the piping around the bolt holes to make sure you can get the nuts on the studs.

A thought : Switch from the stud and nut configuration to Stainless socket head cap screws. The head is much smaller than the nut, plus your wrench is smaller yet so your pipe can go right out to the bolts.
I'd consider putting an EVO or other O2 housing on it while your at it, or go nuts and eliminate the O2 housing all together and just bring the DP right up to the turbo. If you're going wideband or already have, it flows like nothing else and you can put the O2 bung farther downstream.

 

[wvturbo2]

I say make your own o2 housing while your making the Downpipe.

 

[xveganxcowboyx]

A thought : Switch from the stud and nut configuration to Stainless socket head cap screws. The head is much smaller than the nut, plus your wrench is smaller yet so your pipe can go right out to the bolts.
I'd consider putting an EVO or other O2 housing on it while your at it, or go nuts and eliminate the O2 housing all together and just bring the DP right up to the turbo. If you're going wideband or already have, it flows like nothing else and you can put the O2 bung farther downstream.

It's not a bad idea, but if you are using the stock flange it won't really make any difference. You only have to dimple it a little bit and unless you widen the opening on the flange the pipe is still larger even at the narrow area. Once dimpled you can take it off and put it back on with ease. Access is not a problem.

Of course using a better O2 housing is always a great idea as is eliminating it. I'm waiting for a bigger turbo to do that.

 

[speedy13]

http://www.roadraceengineering.com/flangesandgaskets.htm

RRE has everything you need.

 

[LordZed]

Hmmm...I do plan on going wideband. That's a really good idea. I may try to eliminate it all together. It would test my welding skils!

 

[wishihadatalon]

Hmmm...I do plan on going wideband. That's a really good idea. I may try to eliminate it all together. It would test my welding skils!

You will absolutely hate removing your down pipe if you go this route. I have a 3" o2 eliminator from RNR racing and it takes quite a while and many scratches on my arm to get the down pipe down.

 

[LordZed]

You will absolutely hate removing your down pipe if you go this route. I have a 3" o2 eliminator from RNR racing and it takes quite a while and many scratches on my arm to get the down pipe down.

oooooh boy! That sounds like so much fun!
So should I buy a whole new O2 flange, or just take the one I have, chop off all the pipeing, and make my own flange to weld the new pipes to?
I suppose if there cheep i should just buy a new one and start from scratch huh?

 

[the_skin_eater]

^^ ya...More work to try and re-use than to just buy a new one.