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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 04-27-2008, 01:16 AM   #1
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Default Building a manifold

Been looking for a used BEGI or FM manifold to no avail. I'm not adverse to building my own. I have a metal bandsaw, grinders and a nice Miller TIG at home, so equipped to do so.

I have a couple of questions.

1) Has anyone cut up a stock exhaust manifold for the flange plate and used it in a turbo manifold? Does anyone know what kind of steel it is?

2) The stock manifolds get by without expansion cuts between ports, but all of the turbo manifolds that I have seen have been separated with a saw cut. How do the stock ones get by without this? Is it because they are tubular and can handle the movement from expansion? It still doesn't answer the stud shearing question on the stock one.

3) I have an extra head from a 96 that I was going to use for a fixture for holding/clamping the manifold while welding. Is the exhaust side of a 96 head exactly the same as a 99? I'd hate to build it up and have an issue.

4) Would I be completely wasting my time building a mild steel weld el manifold or do I have to go to stainless? I'm not set up to back purge stainless, but could probably rig someting if I have to. Also, if the stock flange can be used and is stainless, I guess I have answered my own question.
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Old 04-27-2008, 01:48 AM   #2
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Uh, I've seen it somewhere where a guy cut off the flange of a stock miata header and used it for his turbo manifold. Hmm, might do that...

Pretty sure the exhaust ends are the same. A turbo manifold that fits a 1.8 fits them all, though I suspect the ports *could* be slightly different. I'm port matching my flange to the head.

It wouldn't be a complete waste of time. I was gonna build one from steel, but then decided to use stainless instead. Hell I may end up using steel, I dunno. I need to do more research but I think I read the SS is more resistant to cracking.
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Old 04-27-2008, 02:01 AM   #3
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maybe turbo manifolds get a bit hotter because of all the restriction of the turbo and thats why they need expansion cuts. wouldnt hurt to add them in once the manifold was finished.
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Old 04-27-2008, 02:15 AM   #4
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Short, cast manifolds are brittle relative to tubular. When a manifold heats up, it expands. A tubular manifold like the stocker isn't affected by this much but a stubby cast one like a Greddy is, so relief cuts are made. That's my theory anyway.
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Old 04-27-2008, 03:28 AM   #5
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I don't think you would need to backpurge all the way. May be only when you will weld the 4 into 1 coupling but even there, you will weld surely sch 10 pipe so if you pass through that and make sugar you sure have welded too damn hot! What you can do is welding a quart of the radius of the pipes, cool it with air, weld, cool, weld, cool. If you absolutly want backpurging, just tack the entire manifold, and make you a block plate for the head flange and one for the turbo flange with a hole with threads and put a plug with a hose connected to your bottle of argon. At least, that's the way I would do it, but I never did it myself so i'm not much a good reference for it!

Last edited by Dark Wanderer; 04-27-2008 at 12:35 PM.
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Old 04-27-2008, 11:06 AM   #6
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Stein,

I believe all 1.8 manifold flanges are the same. You can buy premade flanges a few places though (JGS, ETD, maybe more).

Also check around either mcmaster or a local plumbing supply store for some pipe weld elbows. Those are going to be the right thickness ( to build your mani. It's also what most shops build them with. Vibrant also has them.
http://vibrantperformance.com/catalo...df6970ba11d1f9

You aren't wasting your time with mild steel. I've had mine on the car for years and 10s of thousands of miles and it's been solid as a rock. get the outside ceramic coated though. it looks much nicer and will better manage the heat.

I'd probably start by talking to TurboTim about components...

Matt
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Old 04-27-2008, 01:50 PM   #7
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If you go with mild getting it coated is recommended but for minimal cost increase you can use stainless weld-els and be better off in the end.
WEIR makes cheap flanges ($24) but the OEM flange will work just fine. The 99-00 cast iron manifold obviously doesn't have a flange you can use though. WEIR can be found on the forum but you can also reach him at homemadeturbo.net.
ETD racing doesn't cut their flanges between runners and doesn't recommend that the buyer do it either for some reason. Apparently they've had more issues with cut flanges than not cut ones.
You can use SCH10 of SCH 40 1.5" pipe, SCH10 is lighter and strong enough for turbo manifolds though.
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Old 04-27-2008, 02:39 PM   #8
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The cast iron used in turbo manifolds has (or should have) a high nickel content, giving it good corrosion resistance at temperature. Mild steel or non-nickel cast iron has very little corrosion resistance. Basically, it will begin rusting instantly in fresh water if it's not coated with something, and in air only slightly slower. If you have to go with mild, go with Sch 40.

I'd stick with the 316L weld-els for a manifold, as they're only 10-20% more than 304 and have better corrosion resistance. Sch 40 might let you get away with not bracing it properly. Sch 10 is plenty strong if it's braced right.

Cutting the corner and failing to back purge stainless will let you put something together that will work for a while, but the oxides that are formed have very little corrosion resistance, so you're asking for cracked welds over the long haul.

If you're a perfectionist, using mild steel els and PVC straights would keep the costs way down for mocking it up the first time. You could replace the PVC with mild straights and practice welding some of the trickier access spots without having to back purge, and with low scrap costs if you f(*& it up the first time or two.
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Old 04-27-2008, 03:17 PM   #9
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zabac can get you a flange for sure if you need one.
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Old 04-27-2008, 05:40 PM   #10
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a manifold with PVC pipe? interesting.
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Old 04-27-2008, 07:57 PM   #11
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Quote:
Originally Posted by y8s View Post
a manifold with PVC pipe? interesting.
I was talking about just a mockup. It's easier to cut and costs almost nothing, so you can play with it until you get your straight lengths perfect and not run out of patience and hate yourself later. If you were going to weld up the mild, you'd of course replace PVC with steel. Gosh...
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Old 04-27-2008, 09:12 PM   #12
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As cjernigan mentioned, this guy makes flanges for so cheap, it doesn't make any sense at all to go through the hassle of cutting the stock one off. Might as well sell the stock one to recoup the cost of the flange:

http://www.homemadeturbo.com/forum/i...?topic=83018.0
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Old 04-27-2008, 09:27 PM   #13
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yeah, i've got lots of the bp flanges as well as b6t's in stock. they are $22 plus shipping. as you can see i've got quite a variety of flanges:



coincidence, i've just started mocking up a bp manifold this weekend. i'm probably going to make a jig for it as well. i don't really know the miata market a whole lot though, so i'm not sure who would really be interested in something so elaborate, most miatas i know are ripping around cones, or a road course, not a drag strip. this manifold isn't even for the owner of the car, i was just doing a dp for him with his edt manifold (crappy design imo) and thought since i had the car in the shop, i might as well use it to rip off a mock up quick.



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Old 04-27-2008, 09:38 PM   #14
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If you can make a manifold that will work easily with powersteering and A/C while having good clearance to fab a downpipe then you will have a product that sells.
If you can make a manifold and offer a downpipe for both T25s and T3s then you'll really have a product that will sell.
Make a combo that will sell for less than $1k and you'll get some interest from people looking for big power off the shelf.
There are currently a couple companies offering mani/DP combos, FM and BEGI, so it would be nice to have another in line.

The DP for that manifold is going to be interesting.
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Old 04-27-2008, 11:05 PM   #15
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I am late for this thread, but Aaron(weirtech) makes flanges for $22+shipping, that's worth it to me to leave my OEM mani in one piece if I need to go N/A...
As far as weldes go, acestainless.com is pretty damn good. (stainless or mild)
A flange from weir and your sch40 from ace beats the crap out of the JGS kit as well in case anyone wandered...

Stein, what I did is order a (mild) flange from weir and plan on getting (stainless) weldels from ace and mocking up my own mani, and since I cannot weld nor have the means to try it and teach myself, I will find someone (proffesional) to TIG it all up.
Good Luck to ya.



PS-does that Miata have a GS rad in it? lol

Last edited by Zabac; 04-27-2008 at 11:24 PM.
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Old 04-27-2008, 11:13 PM   #16
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actually, the ac compressor isn't in there, so when the customer comes to pick the car up i'll ask him to bring it. i know where it goes, just not sure what it looks like.

do you think the manifold will clear it? the runner that will be closest to it is the one towards the front of the car. the one incomplete is going to #2 up behind the collector...

as for the dp, you can see the runners that are going to #3 and #4, pretty straight forward, so basically all the room you see in the third pic is what you will have for a dp and a wg dump tube... i think it is quite a bit of room... certainly more than the etd manifold!
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Old 04-27-2008, 11:25 PM   #17
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Hey weiRtech, do you sell the weld ells too? I was going to buy the flanges from you guys, and some weld ells elsewhere, but as the multiple shipping charges add up the JGS kit begins to have its appeal. I basically need everything to build a log style manifold. Thought about sending you a PM instead but I'm sure everyone else wants to know too.

Thanks.
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Old 04-27-2008, 11:55 PM   #18
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Quote:
Originally Posted by Zabac View Post
I am late for this thread, but Aaron(weirtech) makes flanges for $22+shipping, that's worth it to me to leave my OEM mani in one piece if I need to go N/A...
As far as weldes go, acestainless.com is pretty damn good. (stainless or mild)
A flange from weir and your sch40 from ace beats the crap out of the JGS kit as well in case anyone wandered...

Stein, what I did is order a (mild) flange from weir and plan on getting (stainless) weldels from ace and mocking up my own mani, and since I cannot weld nor have the means to try it and teach myself, I will find someone (proffesional) to TIG it all up.
Good Luck to ya.



PS-does that Miata have a GS rad in it? lol
For $22, it doesn't seem worth it to do the stock hack job. As for the earlier post about the 99 being cast, I have stock 95 and 96 manifolds to work with.

Zabac:

You said you were getting a mild steel flange and going with stainless weld els. Aren't you worried about dissimilar material compatibility?

This was one of the reasons I considered an all mild steel manifold, plus the backpurge issue, plus the extra cost, plus tougher to keep the stainless from cracking.


Weirtech will probably see an order shortly as soon as my turbo and DP arrives so I can get a look at everything. I'm going to check around locally on the weld els just in case I can save the hassles of shipping, but acestainless has good prices.
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Old 04-28-2008, 12:56 AM   #19
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See if you have a Fastenal around you, I know they can order them if they don't have any in stock.
As far as different materials go, I'm not too worried as a friend of mine just did this and has had no issues thus far. Plus Sch40 is pretty damn thick, I am not worried about it cracking. I will brace the flange properly when welding the runners to the flange so it should not warp much due to the higher heat required for welding SS.
I could go horribly wrong with this and waste a bunch of money on all the weldels, but as I have seen this done, I am not too worried.
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Old 04-28-2008, 01:29 AM   #20
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Welding stainless weldels to mild flanges is common practice. Stainless flanges are super expensive and supposedly warp easier when welding. You bolt the flange down and resurface it anyway but you understand. You just use the correct rod when tig welding and there are no issues with cracking or dissimilar metals.
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