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-   -   DIY SS Bottom Mount Manifold (https://www.miataturbo.net/diy-turbo-discussion-14/diy-ss-bottom-mount-manifold-40820/)

SKMetalworks 12-03-2009 02:50 PM

Can't wait to see it.

wayne_curr 12-03-2009 03:06 PM


Originally Posted by sbkcocker499 (Post 490380)
Can't wait to see it.

Ya this whole having a job thing is really taking a toll on my progress. I dont have to go to work til 2pm and keep thinking i'll have all morning to work on it but I just feel like being lazy all morning instead of working on anything.

Plus its freezing fucking cold in my garage right now.

Going to the hardware store today to pick up 3/8-24 studs, a tap and a drill bit.

Question for you experts on building a downpipe: Do you start at the exhaust and work your way to the turbo or vice versa? Or do you start both ends and meet in the middle? Been developing my plan of attack in my head the last couple days.

JKav 12-03-2009 03:50 PM


Originally Posted by rrjwilson (Post 489589)
But why does this manifold have cuts (for the Greddy reason?) around the bolt holes?

Cuz its easier/faster/cheaper to cut the flange this way.

The head flange is laser-cut. Or watterjetted, but probably laser. Either way, the little slots for each hole means the laser can cut the outside profile of the flange AND cut the bolt holes in one continuous pass.

TurboTim 12-03-2009 04:44 PM


Originally Posted by JKav (Post 490427)
Cuz its easier/faster/cheaper to cut the flange this way.

The head flange is laser-cut. Or watterjetted, but probably laser. Either way, the little slots for each hole means the laser can cut the outside profile of the flange AND cut the bolt holes in one continuous pass.

ahhhhhhhhhhhhhhhh I didn't think of that but it makes a ton of sense. Thanks!

TurboTim 12-03-2009 04:45 PM


Originally Posted by wayne_curr (Post 490396)
Ya this whole having a job thing is really taking a toll on my progress. I dont have to go to work til 2pm and keep thinking i'll have all morning to work on it but I just feel like being lazy all morning instead of working on anything.

Plus its freezing fucking cold in my garage right now.

Going to the hardware store today to pick up 3/8-24 studs, a tap and a drill bit.

Question for you experts on building a downpipe: Do you start at the exhaust and work your way to the turbo or vice versa? Or do you start both ends and meet in the middle? Been developing my plan of attack in my head the last couple days.

I start at the turbo and work my way towards the cat. The cat/catback has a lot more slop than the turbo & manifold.

SKMetalworks 12-03-2009 09:11 PM


Originally Posted by wayne_curr (Post 490396)

Question for you experts on building a downpipe: Do you start at the exhaust and work your way to the turbo or vice versa? Or do you start both ends and meet in the middle? Been developing my plan of attack in my head the last couple days.

I build starting from the turbo also. Im also american and read from left to right so maybe that has something to do with it ;)

wayne_curr 12-03-2009 10:48 PM

Ok thats what I thought as well. Was just checking my logic.

I got 2 of the new studs in the manifold (after drilling/tapping) but there isn't really any room to fit a box ended wrench in between the turbine housing and the stud to make use of Tim's nuts. I'm considering grinding some of the casting away. We'll see.

rrjwilson 12-04-2009 08:48 AM


Originally Posted by JKav (Post 490427)
Cuz its easier/faster/cheaper to cut the flange this way.

The head flange is laser-cut. Or watterjetted, but probably laser. Either way, the little slots for each hole means the laser can cut the outside profile of the flange AND cut the bolt holes in one continuous pass.

Are you sure that is the only reason because that doesn't hold much faith for me. Greddy units were always cracking due to heat or bad design or bad manufacturing (whatever the end cause will be diagnosed as).

Easier - Ease would be from design front as cutting as like saying print and those slots will be more effort once the manifold design has been finished.
Faster - More cuts should equal more time but as you say one pass means less travel but given the speed of waterjets I doubt that 10 seconds would matter much.
Cheaper - Doubt it given cost of metal and time will be irrelevant as cuts are the same.

Admittedly the slits may help by allowing slight variance in head mounting holes but that seems to be only reason to CAD them in except for some thermal effects. Is the reason Tim and Curly have these cuts because they bought from the same supplier? I've got my own CAD files for 1.6 intake and exhaust which I've had cut into 1/2" thick steel plate for £80 (including T25 flanges and a custom 3" flange which I'm using to build an active exhaust). Seems like price for work isn't the problem or at least in the UK. Tim?

I really am enjoying this thread it's too wet here for me to start me build so I'm very excited to see such good work from someone with little experience like me (gives me hope :D).

cjernigan 12-04-2009 01:48 PM


Originally Posted by wayne_curr (Post 490648)
Ok thats what I thought as well. Was just checking my logic.

I got 2 of the new studs in the manifold (after drilling/tapping) but there isn't really any room to fit a box ended wrench in between the turbine housing and the stud to make use of Tim's nuts. I'm considering grinding some of the casting away. We'll see.

What about grinding down an expendable wrench? Might be able to make the box end thin enough to make use of it instead of grinding the housing. or grind a wrench and clearance the housing instead of removing all the material from the casting.

wayne_curr 12-04-2009 02:56 PM


Originally Posted by cjernigan (Post 490897)
What about grinding down an expendable wrench? Might be able to make the box end thin enough to make use of it instead of grinding the housing. or grind a wrench and clearance the housing instead of removing all the material from the casting.

I'm considering it. I had to do this once already with a 14 to get my BEGi mani off and on. I guess it wont hurt to do it again.

wayne_curr 12-09-2009 11:32 PM

4 Attachment(s)
Woohoo! Update! Warning: Newb welding content.

Downpipe just about done. Going to grind down some of the welds to make sure there aren't any leaks and perhaps pretty some of them up.

Attachment 201923
Attachment 201924

Some closeups of a couple of my best beads.
Attachment 201925
http://img.photobucket.com/albums/v6...r/DSC01657.jpg
Attachment 201926

I've got about 30-40 minutes of actual welding experience at this point. I start rough when I begin welding and as I get some practice I get better. Some of the welds on the downpipe look like total shit because of my newbishness in cutting and fitting so there were big gaps to fill. Next time i'm doing this with a chop saw. No more cutoff wheels on the angle grinder.

Jeff_Ciesielski 12-09-2009 11:35 PM

AWWWWW SHIT. I see v-bands :).

wayne_curr 12-09-2009 11:58 PM


Originally Posted by Jeff_Ciesielski (Post 493389)
AWWWWW SHIT. I see v-bands :).

Yep :) It takes less than 60 seconds to put this downpipe in. Its an amazing experience versus the Begi downpipe which took roughly 48 hours and an act of god to get in and out.

Incidentally, I love the DIY aspect of being able to incorporate neat features like v-bands without that outrageous cost of paying someone else to make it all. Been a really fun build except that the cold outside is oppressive. Luckily my friend's kerosene heater keeps the garage just warm enough to kind of see some breath, but just barely.

Then you open the door to let all the welding smoke out and its freezing cold again in seconds :(

TurboTim 12-10-2009 12:02 AM


Originally Posted by wayne_curr (Post 493387)
Next time i'm doing this with a chop saw. No more cutoff wheels on the angle grinder.

Cutoff wheels on an angle grinder are for cutting shapes into your weld ells on the manifold. Straight (perpendicular to the pipe) cuts like downpipes are to be done on the chopsawwwwwwwwwwwwwwww

Looks like a great first start! Good job. EDIT: and definitely nice using v-bands!!

mafoose 12-10-2009 12:22 AM

Sorry if I missed this, but what are you welding this with?
Looks functional and I agree, v-band downpipes are the shit!

wayne_curr 12-10-2009 01:26 AM


Originally Posted by mafoose (Post 493408)
Sorry if I missed this, but what are you welding this with?
Looks functional and I agree, v-band downpipes are the shit!

Its a millermatic 130 or something like that. A mig welder.

thesnowboarder 12-10-2009 02:41 AM

wow man thats awesome, wish my welder had argon :(

absRTP 12-10-2009 09:54 AM

look's sexy! nice job, I'll have to do mine too next summer :P

SKMetalworks 12-10-2009 12:22 PM

Looks great

wayne_curr 12-10-2009 02:57 PM

Thanks guys. After I tidy up this downpipe and put in an O2 sensor bung all I need to do is figure out how i'm re-routing my coolant/modifying my mixing manifold. Thinking of freeze plugging the existing heatercore return hole and drilling/tapping a new one on top for a barbed fitting.


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