(Quick Fab) China Manifold Replacement
 

Despite all the warnings I, like so many others, purchased a chinafold.
I need to learn the hard way, that's just how I am.
So i finally I got tired of the mess I was creating under my hood with failed reinforcement attempts. This was the last straw.

I've been meaning to place an order with Stahl for some mandrel pieces and the flanges, for a proper header build, but I've been procrasterbating allot lately.
So on my day off, armed with my welder, some 2" aluminized pipe, and a crush bender, i started to craft my own.

I started by making a jig:
https://www.miataturbo.net/attachmen...ine=1378258972
https://www.miataturbo.net/attachmen...ine=1378258972


my plan was to reuse the flanges: (cut and cleaned them up a bit)
https://www.miataturbo.net/attachmen...ine=1378258972

I was weary about using the flanges with the mild steel. I figured that would be my weak point.

The bender limited me to a 6" radius bend( to wide for a manifold).

My solution was to bend the pieces, cut the radius's short, then swell the ends to maintain a constant radius of about 2".

By all means this is not the right way to do this, this is just a temporary solution brought on by weeks of frustration.

My original plan was to create a log manifold but i got carried away.

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

Like i said earlier this is not correct way to fabricate a manifold. I took no consideration for the runner length. I just made sure the collector wasn't creating a mess of turbulence between 1 and 4.

After it was welded together i was able to port the flanges quite a bit to accommodate the larger runners.

Comparing the 2 manifolds:
https://www.miataturbo.net/attachmen...ine=1378258972

My welds started to get sloppy towards the end. It was pushing midnight and I was getting tired.

installed:

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

https://www.miataturbo.net/attachmen...ine=1378258972

I header wrapped it shortly after this photo.

All in all it was a fun experience, and I now have a nice jig to work with when the real parts get here.

So far Its been almost 1k miles and no cracks. Which is better than the chinafold did. The tone of the exhaust is much different than before. Most likely because of the size and unequal length of the runners. Its much deeper now and has a subaru boxer rumble at 4k rpm and up. Very unique in my opinion. I will be taking it to the drag strip tomorrow night to see how my time will be effected by this new custom addition.

p.s. Power seems just as good, if not better than before, but its hard to say since its been a hot couple of days.

Hope this was a somewhat interesting read for everyone.

you could have made the collector shorter to give the runners a little more radius and a straighter shot to the turbo but its better than some of the other manifolds ive seen here.

Really? Show me one.

...Wow..

Dann

+1


And that's by no means dissing you OP. Good job with building something for yourself. With probably $10 in material there, it is good practice for when the nice good stuff comes. Which i hope turns out nothing like this. haha

I give you props for doing it, but I wish you tried a little harder.

Technically not from this site but it was posted here...

https://www.miataturbo.net/attachmen...icture011-jpeg

I'd prefer that one.

why? the 1 and 4 runners are perpendicular to the turbo inlet and inline with eachother. While not pretty, at least the OP doesn't have exhaust gases flow opposing each other

Lol! I'm waiting for "nothing is good enough for you guys". I can't wait to post pics of my new setup so I can get props for trying, but critized at the same time.
Props on making that jig. What type of welder did you use? Obviously it was mig, but I mean, was it a small 110v unit?

Given the nature of the project being a quick temporary fix I thought it was a success. Definitely an entertaining read with the funny pictures. I feel like if I actually tried with my current fabrication abilities I would end up with a product similar to or worse in quality especially if I did it all in one day.

they aren't flowing "into" each other; they won't collide like atoms and explode. #1 and #4 don't fire at the same time so it doesn't even matter.

But if that's your argument for what makes one better than the other, I suggest you look closely at OP's #1 and #4 as well.

they don't fire at the same time but a car reving at 6000 rpm will fire each cylinder 50 times a second. or once every 20 ms. I don't think 20ms is enough time for all the gas to escape. And they won't explode but im pretty sure you'll get very inefficient turbulent flow at the collector and the turbo won't spool as quickly with the air molecules loosing velocity (energy) in order to get redirected down towards the turbo.


edit: OP's isn't much better but that second manfold almost looks like it directs the exhaust gas away from the turbo. The OP's is at least partially angled toward the turbo

true: I had a log manifold once, the turbo wouldn't spool; the exhaust clogged the outlet like I clog my toilet.

Are you not seeing the OP's collector?

Ever notice that when the clog finally gets overcome, the water rushes REALLY hard?

Clearly the clog is key to peak power.

I'm going to be in OC next week. has i can the old manifold?

touche. so I guess not a big deal in the larger scheme of things...

but still: log mani < random manifold < OP manifold < all other well designed manifolds?


Also last time I had toilet clogging problems my land lord told me to keep a tree branch in the bathroom and poke at the stool till it goes down (true story).

Well there's your problem. Stop putting your stool in the toilet.