DIY Greddy downpipe for a first-timer. - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Fabulous Fabrication Post all your custom fabrication projects here; impress all your friends.

Reply
 
 
 
LinkBack Thread Tools
Old 11-17-2014, 09:00 AM   #1
Newb
Thread Starter
 
Join Date: Nov 2010
Location: Yorkshire, UK
Posts: 36
Total Cats: 12
Default DIY Greddy downpipe for a first-timer.

I want to replace my stock Greddy downpipe with something custom. You all know how restrictive it is.

Stock looks like this - (photo stolen from Hornetball - no your not the last one left if you count the UK!)

Name:  IMG00014-20110219-2226.jpg
Views: 67
Size:  35.4 KB

And I'm looking to change it to 2.5" , to match the rest of the system, something like this infamous tony DP -




Now I have a MIG. My dad welds well (Mig, tig, arc, braze etc,) and has given me it, to learn with. I can throw sparks and make things stick together. I'll get better.

I have a mild steel flange. I will be putting a flexi in and some way of better supporting it in place of the OEM bell housing bracket. I can get some 2.5" tube and bends easy. I guess I'll need one tight bend to come straight off the flange.

My first bit of proper fabrication. A learning exercise. Where the best way to start?

Remove original stuff. Bolt flange to turbo. Start cutting. Tack first section. Keep going till the ends meet up. Take it all off and weld up properly.

Any advice? Just go for it?

The existing setup is 2 pc - Greddy pipe, stock pipe to the cat. Doing it in one piece is going to make it a lot harder to fit, right? I guess that pictured ^ has to be snaked in from below with the turbo off.

Would it be sensible to tack it up in one piece, then if I wish to split it, just cut and add two flanges?

I'll be sure to post photos once I've started!
snotrag is offline   Reply With Quote
Old 11-17-2014, 10:45 AM   #2
Senior Member
iTrader: (3)
 
Join Date: Apr 2011
Location: Volo, IL
Posts: 1,247
Total Cats: 140
Default

In for not being the only one dumb enough to do this.

I'm doing the exact same thing starting in a week or so. I can't weld very well, but I have access to a lot of welding equipment and an endless supply of SS pipe. I'll be spending the winter attempting to fab a good downpipe.

There are more of us than you may think, but we tend to hide our Greddy shame from the limelight.
dieselmiata is offline   Reply With Quote
Old 11-17-2014, 11:09 AM   #3
mkturbo.com
iTrader: (24)
 
shuiend's Avatar
 
Join Date: May 2006
Location: Charleston SC
Posts: 13,778
Total Cats: 1,106
Default

I would search for pictures of the TurboTony greedy replacement downpipe and copy that.
shuiend is offline   Reply With Quote
Old 11-17-2014, 11:45 AM   #4
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,010
Total Cats: 583
Default

There's also the BEGI SG Greddy DP replacement. A more complicated welding project, but gave nice gains.
hornetball is offline   Reply With Quote
Old 11-17-2014, 05:08 PM   #5
Newb
Thread Starter
 
Join Date: Nov 2010
Location: Yorkshire, UK
Posts: 36
Total Cats: 12
Default

Cheers guys, I think that one in the 2nd photo is a Tony pipe?

I also looked at the BEGI piece, its still listed on their site, but with import duty etc it would be a small fortune to get one to the UK.

The flange I bought would suit that type - I haven't decided yet, but I can always cut away but can't add material. Sketched it out today ready to scan in to Solidworks at work tomorrow, because... well, because i can.

snotrag is offline   Reply With Quote
Old 12-04-2014, 04:46 PM   #6
Senior Member
 
Join Date: Apr 2011
Location: Martin, Slovakia
Posts: 513
Total Cats: 71
Default

Simon, I am curious if you considered making a replacement manifold?

The downpipe is comparatively straight forward for the 15g with an axial mount manifold. This is a similar setup I am working on atm

Name:  P1060579_zpsf93f7489.jpg
Views: 47
Size:  101.1 KB
sturovo is offline   Reply With Quote
Old 12-05-2014, 07:29 PM   #7
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,640
Total Cats: 25
Default

When you say axial log, you mean a log specifically with the flange welded directly to the log itself?

Dann
nitrodann is offline   Reply With Quote
Old 12-06-2014, 03:36 AM   #8
Senior Member
 
Join Date: Apr 2011
Location: Martin, Slovakia
Posts: 513
Total Cats: 71
Default

Yes Dann that is what I meant. Axial doesnt mean too much.
Mid mount would be a better description?
Making a downpipe for the original Greddy top/aft mount manifold is much more difficult than for a mid mount manifold.
I never understood the Greddy turbo placement. Was it re-purposed from another application?
Name:  P1060613_zps0dfe93b5.jpg
Views: 49
Size:  53.5 KB
sturovo is offline   Reply With Quote
Old 12-06-2014, 10:04 AM   #9
Cpt. Slow
iTrader: (25)
 
curly's Avatar
 
Join Date: Oct 2005
Location: Oregon City, OR
Posts: 12,107
Total Cats: 518
Default

No idea, but it's ****. Mounted far back and high, so the downpipe always has to be a ? shape. Huge compromises are made everywhere in terms of size, location, bends, heat, etc.

My side mount downpipe looks like a straight piece of pipe compared to my old greddy.
curly is offline   Reply With Quote
Old 12-06-2014, 10:58 AM   #10
Newb
Thread Starter
 
Join Date: Nov 2010
Location: Yorkshire, UK
Posts: 36
Total Cats: 12
Default

If you look at an engine bay with a 'stock' Greddy setup it makes sense - they designed this way back when to work with the stock cross over pipe (I think?) and also requiring the cast U-bend for the AFM.

Obviously without these limitations, there's better places to put the turbo.


And - please stop putting ideas in my head .

I'll stick with just a down-pipe for now, in the future, who knows...
snotrag is offline   Reply With Quote
Old 12-06-2014, 12:31 PM   #11
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,892
Total Cats: 1,792
Default

why does it curl back? to clear the shelf?
Braineack is offline   Reply With Quote
Old 12-06-2014, 05:08 PM   #12
Cpt. Slow
iTrader: (25)
 
curly's Avatar
 
Join Date: Oct 2005
Location: Oregon City, OR
Posts: 12,107
Total Cats: 518
Default

Yeah. To make one without curving back would need a L shaped downpipe. Someone here did that and it immediately glowed red due to the turbulence. Levubin or whatever it's called?
curly is offline   Reply With Quote
Old 12-06-2014, 10:11 PM   #13
Free Moustache Rides
iTrader: (8)
 
matthewdesigns's Avatar
 
Join Date: Jun 2008
Location: Colorado Springs
Posts: 1,656
Total Cats: 49
Default

Quote:
Originally Posted by snotrag View Post
Cheers guys, I think that one in the 2nd photo is a Tony pipe?
Yes it is, in fact the one I sold last month
matthewdesigns is offline   Reply With Quote
Old 12-07-2014, 10:32 AM   #14
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,892
Total Cats: 1,792
Default

here's what you do:

bolt a plate on the current outlet. Tap side of manifold. :P
Braineack is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 59 Yesterday 09:00 PM
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
Back to Stock Part Out!! Turbo Parts, MS2 Enhanced 01-05, Suspension, and MOAR! StratoBlue1109 Miata parts for sale/trade 16 10-02-2015 10:39 AM
1996 Turbo Build Goldwar DIY Turbo Discussion 2 09-29-2015 10:20 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 05:35 AM.