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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 09-16-2009, 04:41 AM   #1
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I should have my pipe welding certification by the end of the year. My stick and MIG welds have improved vastly, and I've had a long battle with the turbo bug and lost (82 Turbo 280zx, 78 280z+t, 76 280z turbo swap, 93 SE-R SR20DET swap).

All those cars except the Sentra ran Megasquirt assembled by me and tuned by myself.

So now I want to take it one step further. I want to design and build my own turbo manifold.

Here's what I have so far for wants/design:
-Water jet cut flange
-Weld el pieces
-Close to equal length
-T2 flanged (only looking for ~250hp)
-Welded by myself using solid core CO2 shielded GMAW

Here's what I need help on:
-How thick should my head flange be
-Collector design
-Bottom or top mount (must be A/C PS friendly, it's my first car that has had both and I'd like to keep them)
-The exhaust ports are oval, are the head flanges beveled to make them round or are the runners oversized to create a step for anti-reversion?

Now, I might have a line on a 1.6 engine that I could use for mockup. How's the port size compare on the 1.6l to the 1.8? What about placement? According to a thread I found on here, the manifolds between both are interchangeable, it's just that the stud holes are in different places. Is that correct?

I haven't decided on a collector design just yet. I've seen a few different DIY setups online and haven't decided which to use.
If I wanted to go a little further and do a divided turbine, what should the collector division be?

I plan on design everything and keeping a log of it here. If at the end it works I'll even post plans and materials if you wanted one for yourselves.

Any more ideas or thoughts?
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Old 09-16-2009, 05:44 AM   #2
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There are literally over 50 threads answering almost every single one of your questions. My manifold, p51shellfires, and Steins are almost identical. All clear ps/ac. Check them out. All of us, however, have different intercooler routing. We ordered our supplies from Weirtech and Ace stainless. Flanges, weld els, everything you can possibly think of can be purchased from both companies.
Then theare are ones from jgs that people have put together that are not as smooth (or so it seems) but get the job done just fine.
There are also a few absolutely baller designs such as TurboTims absurdflow and a few others that are top notch: v-banded, excellent flow, etc etc etc. Check those out too.
It comes down to how good you are and how much time/money you want to invest. Everything from the basic jgs log mani to an absurdflow are all at your fingertips.

The amount of manifolds I've seen just over the past few months makes my head spin. And don't get me started on intercooler routing/setups.The possibilities are endless.
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Old 09-16-2009, 09:07 AM   #3
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Thanks for the compliments 18psi I'll add that the 1.6 flange & port spacing are not close to the 1.8. Do not use a 1.6 head to mockup your manifold if you want to ultimately use it on a 1.8. I run 3/8" head flanges but 1/2 may be better.
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Old 09-16-2009, 03:56 PM   #4
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3/8 is the standard for head flanges. For the smoothest transition, you want a CNC'd flange similar to this:



You're gonna have a hard time making an equal length manifold that works with a/c and ps. It'll definitely have to be top mount. IMO, I would at least get rid of power steering and make it a bottom mount. A "ramhorn" manifold is close to equal lenght and fairly simple to make. You need 12-13 weld-el 90's. A 4>1 collector with the smallest merge angle is the best flowing, but packaging becomes a problem. I think you can fit a 4" collector with a 18 angle in a bottom mount with a/c

For a divided collector you want to pair 1/3 and 2/4. This will add a lot of complexity to the manifold design though, and I'm not sure a t2 twin scroll turbo exists. That doesn't mean there aren't benefits, but probably not as noticeable on something this small.

BP uses wider spacing.
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Old 09-16-2009, 04:20 PM   #5
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Quote:
Originally Posted by ARTech View Post
For a divided collector you want to pair 1/3 and 2/4.
I'd pair 1&4, 2&3 personally.
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Old 09-17-2009, 12:29 AM   #6
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Thanks 18psi for suggesting yours and Stein's manifolds. And TurboTim your manifolds are sweet!

18psi, I take it you used 1.5in Weld els like Stein? The ID on those SCH 10s SS are just a little bit bigger then the mild steel SCH 40s so I think I'm going to use those (I don't have the tools to weld SS). It might be a pain in the *** making them oval in the right spot though...

I just got done modeling the turbo flange and elbows. I'm going to get a header flange gasket to get the port and stud placement and draw that up. If it wasn't so damn hot during the day I'd measure out the space available to me so I could make a bounding box.

18psi, did you have any issues with all that brake hardware so close to the turbo/dp?

On other thing, is a non-90deg bend downpipe only possible with a bottom mount? In other words, am I not going to be able to make one since I want to keep A/C and PS?

Also, damn those Weirtech flanges are cheap! I've got a friend who runs a waterjet and I think he'd even have trouble matching those prices! Also, I guess I couldn't find much of my info since I search for "DIY turbo manifold" instead of "turbo manifold build"...

Depending on how my new job goes I'll hopefully be making more substantial progress in a month or so. Thanks for the comments thus far.
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Old 09-17-2009, 02:54 AM   #7
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Yes I used the 1.5's. Had to crumple them into ovals near the flange.
No issues since I put a heat shield between the dp and the brake lines.
The way we have ours mounted, you have to have a 90 degree dp, or pretty close to it.

Good luck
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Old 09-17-2009, 02:12 PM   #8
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Name:  Bobsmani.jpg
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Seems like you could do something like this just upside down, right?

i've been playing with the idea of copying bob's mani/downpipe as a winter project.
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Old 09-17-2009, 02:44 PM   #9
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Quote:
Originally Posted by wayne_curr View Post


Seems like you could do something like this just upside down, right?

i've been playing with the idea of copying bob's mani/downpipe as a winter project.
That looks interesting, what are his numbers??.

OP I think you could fab up and even sell something like that and make some moola on the side.
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Old 09-17-2009, 08:07 PM   #10
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I was bored and did this quick sketch. The pipes and turbo flange are all to size, but the port spacing and basically everything else is all wrong since I haven't gotten the gasket yet.

I figured out how to "cut" meshes so I can get all my coping measurements out of this when I build it to the right size/spacing. I still need to create a bounding box as well, I wonder how low I can mount it and get away with A/C and PS...
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Old 09-17-2009, 08:29 PM   #11
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Wow, way to disregard everything I said...
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Old 09-17-2009, 08:33 PM   #12
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I've never seen a collector like that, though i cannot think of any reason it wouldn't work.

To avoid the AC/PS, you will want to locate the turbo further back i think.
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Old 09-17-2009, 08:47 PM   #13
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Quote:
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Wow, way to disregard everything I said...
That flange is pretty but I bet a lot more then $24. Considering the 1.5in weld els squash nicely to the port shape is another reason I'm not going to use it.

Like I said it was a quick little thing I did (while I was waiting for the chicken to cook). Nowhere near accurate or final since I don't even have the port spacing yet.

I don't even have the bounding box set yet, but I want to see how low I can go to make a nice DP. You might end up being right and I might have to do a top mount.
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Old 09-17-2009, 09:02 PM   #14
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The flange is actually only $55. A great deal IMO for what it is. Pressing the round ports oval doesnt give a perfect fit, but it does work, and that's what most of us do.

Well, heres a couple of pics to get you started. Room is cramped with a/c and p/s





I suppose you could move the flange towards the firewall to free up some room, either way it will complicate things. I haven't heard anyone complain after giving up power steering.

I know this is far from your final design but the collector in the pic has 1 and 4 pointing almost directly at each other. You dont want that.
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Old 09-17-2009, 09:35 PM   #15
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Quote:
Originally Posted by mafoose View Post
18psi, I take it you used 1.5in Weld els like Stein? The ID on those SCH 10s SS are just a little bit bigger then the mild steel SCH 40s so I think I'm going to use those (I don't have the tools to weld SS). It might be a pain in the *** making them oval in the right spot though...
.
You can go to you welding supply store and Buy SS hard wire for your MIG.You will need 75/25 gas.Welds just Jim dandy.Or just learn to be a TIG god like me.JK,Cuz.
-G-
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Old 09-17-2009, 09:59 PM   #16
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Quote:
Originally Posted by mafoose View Post
I was bored and did this quick sketch. The pipes and turbo flange are all to size, but the port spacing and basically everything else is all wrong since I haven't gotten the gasket yet.

I figured out how to "cut" meshes so I can get all my coping measurements out of this when I build it to the right size/spacing. I still need to create a bounding box as well, I wonder how low I can mount it and get away with A/C and PS...
No offense, but in my honest opinion that looks like crap. Much better designs out there.
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Old 09-18-2009, 09:59 PM   #17
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Quote:
Originally Posted by ARTech View Post
The flange is actually only $55. A great deal IMO for what it is. Pressing the round ports oval doesnt give a perfect fit, but it does work, and that's what most of us do.

Well, heres a couple of pics to get you started. Room is cramped with a/c and p/s





I suppose you could move the flange towards the firewall to free up some room, either way it will complicate things. I haven't heard anyone complain after giving up power steering.

I know this is far from your final design but the collector in the pic has 1 and 4 pointing almost directly at each other. You dont want that.
1 and 4 are connected to 2 and 3 before 2 and 3 are even connected, so they're not. Also, I have got the measurements for the bounding box and better port spacing so I'll take another crack at it.

Quote:
Originally Posted by Reverend Greg View Post
You can go to you welding supply store and Buy SS hard wire for your MIG.You will need 75/25 gas.Welds just Jim dandy.Or just learn to be a TIG god like me.JK,Cuz.
-G-
True, but I'll be using the schools equipment, if they'll let me it might be worth it. Then again, it might be worth it to make it out of mild steel in case it ends up not fitting.

Quote:
Originally Posted by 18psi View Post
No offense, but in my honest opinion that looks like crap. Much better designs out there.
Care to elaborate. I calculated runner length and the 2/3 candy canes are way too big, so I'll shorthen those up considerably with less bends. The reason I did that is to have make up some length since 2/3 tend to be the shortest runners.
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Old 09-18-2009, 10:06 PM   #18
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IMO, equal length is much less important than good collector.
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Old 09-18-2009, 11:58 PM   #19
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Quote:
Originally Posted by mafoose View Post

Care to elaborate. I calculated runner length and the 2/3 candy canes are way too big, so I'll shorthen those up considerably with less bends. The reason I did that is to have make up some length since 2/3 tend to be the shortest runners.
Doesn't look smooth and collector looks weird as hell. I'm going off looks of the "design" which you haven't refined yet so I may be wrong here. Its just not like anything I've seen before and looks a little weird. Why not make the runners more smooth instead of oddly shaped like that?
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Old 09-19-2009, 12:20 AM   #20
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Haters wanna hate; lovers wanna love...
Quote:
Originally Posted by neogenesis2004 View Post
IMO, equal length is much less important than good collector.
Werd.

What is a “bounding box”?

Do you have to use 75/25 when MIGing SS wire? I use straight argon (from the TIG) with poor results but assumed it was the cheap HF machine...??
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