The custom fabrication thread! (Post pics of stuff you have made) - Page 22 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-04-2013, 04:34 AM   #421
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You dont leave any insides at all, you cut them right back to nothing, which is only achievable when you use bends rather than straight pipe for a collector, I see.

Ok so Tim or anyone who can do it how do you guys get a round pipe to fit a T28 flange, a regular one not a split one?

3" pipe has a smaller circumference than the hole, I use the plate you can see to hold it in the vice and just heat and bash, but this doesnt work on bends at all, so for tight fitting downpipe that are close to the shelf pie cuts are always required unless I fork out 300 for a donut...?

Also When I panel beat the resulting pipe back into a circle so it fit the next piece of a downpipe the flange always bloody warps as shown and I need to face it again.





Dann
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Old 05-04-2013, 08:36 AM   #422
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For the bell mouth T28 down pipe flange I use the oval to round piece from ATP if there is room which there rarely is but in your picture above it basically is the same as what you are trying to do. For locations that do not have room for that ~2" long piece, I use ATP's tight radius (3" CLR) 3" mandrel bend and heat & hammer. Yeah the section thickness isn't uniform throughout but so what, it is a nice tight bend. And it is quite difficult to get the down pipe pointing where you want it as you are forming the oval with your hammer.





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Old 05-04-2013, 09:48 AM   #423
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Quote:
Originally Posted by nitrodann View Post
You dont leave any insides at all, you cut them right back to nothing, which is only achievable when you use bends rather than straight pipe for a collector, I see.

Ok so Tim or anyone who can do it how do you guys get a round pipe to fit a T28 flange, a regular one not a split one?

Dann
Well I do leave the inside points, I just cut it out. You see, if you leave it in there, you're forced to weld on the inside of the collector to finish them, and of course you have to weld the inside quarters of each pipe inside of the collector, when you join it to the 4 tubes. My method is to cut out the triangles, weld them onto the finished headers, fully, and then weld the collector on the outside. It saves me at least an hour of tedious welding, and makes for a nicer product.

To answer your question about making a pipe fit, I like to do it like this, with an air hammer and map gas:

http://i104.photobucket.com/albums/m...D0DB07EF58.mp4

Can someone show me how to Imbed the video? I can't ever get it..

Here's the flange after I fused the edge around.


Last edited by Boost_addict; 05-04-2013 at 10:27 AM. Reason: Forgot picture
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Old 05-04-2013, 10:12 AM   #424
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A pencil torch (like weldcraft WP-26P) is what you need to weld inside the collector. Best purchase ever!
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Old 05-04-2013, 10:15 AM   #425
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A pencil torch (like weldcraft WP-26P) is what you need to weld inside the collector. Best purchase ever!
Wouldn't it just be easier to make 4 cuts and do all your welding with ease though?
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Old 05-04-2013, 10:19 AM   #426
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Quote:
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My flanges look like this.



If they were like your id never have asked.

Yours are **** easy where are they from?

Dam I love this thread, wish I had something clever to add :P

Dann
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Old 05-04-2013, 10:22 AM   #427
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Originally Posted by Boost_addict View Post

fark... i do that with a 12mm round bar and a hammer and map gas.

I need to get me one of those that was SOOO easy and fast.

Dann
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Old 05-04-2013, 10:41 AM   #428
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Wouldn't it just be easier to make 4 cuts and do all your welding with ease though?
Sorry, what are you specifically refering to here?

Dann
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Old 05-04-2013, 10:51 AM   #429
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Haven't done much in the last two weeks. Knocked out a reroute spacer yesterday. Need to make the weld-on bung for the sensor.

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Old 05-04-2013, 02:17 PM   #430
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Sorry, what are you specifically refering to here?

Dann
The triangular center pieces from the collector tubes, where they meet and create that long point within any substantial collector. When you weld a whole collector you usually have to get inside of it to finish welding the seams where that point is. It also requires welding the inner portions of the tubing from the header when you attach it, unless you resort to a slip on style collector; a compromise most will make to avoid difficulties. I like to tack those pieces together, and when the whole collector is welded and sanded, I cut it out with a thin cut off wheel.

You can see the collector with the pieces cut off here



Now imagine you have this little pyramid now, and you have your headers totally done, with 4 tubes coming down and ending flush. I clamp all the tubes tight together, and weld on the triangle piece, as well as the "inner" tubing welds, right in plain open space. Then once it's totally welded, I place the collector around it and weld it. The advantages are not having to weld on the inside, which will up your quality unless you're a freakin master. Also not having to rely on slip on joints, or being forced to space out your tubes from one another. You can have them all In contact like this, which makes fabrication easy in turn.. As you only grind it flat until its perfectly in line with the end of the tube. Hope that sums it up.
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Old 05-04-2013, 02:38 PM   #431
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Haven't done much in the last two weeks. Knocked out a reroute spacer yesterday. Need to make the weld-on bung for the sensor.

Ohhh niceee!!! Plan on making any more and if so, how much?!?!
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Old 05-04-2013, 05:51 PM   #432
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Shortnening the collector that far ruins the scavenging properties..
Sorry, but you are wrong.

There is pipe leading up to that always and it still scavanges from the upper manifold.

Matt
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Old 05-06-2013, 06:11 PM   #433
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Sorry, but you are wrong, lol. Scavenging relies on gas velocity. When you pile the exhaust gasses into the turbine housing at sharp angles it loses so much velocity that you lose some of your scavenging. Don't take my word for it, call Burns and ask them to spec you a collector with approach angles that sharp and listen to them laugh at you.


I'm not saying you havn't made power with those, or even that they're not better than some other options, but they're a long way shy of the best possible option.
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Old 05-06-2013, 09:36 PM   #434
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You aren't getting any scavenging on a turbo car. That's how the turbo works, the pressure in the manifold is greater than the pressure in the downpipe. The turbine ruins any scavenging effect.

Equal length is good because the pulses will arrive simultaneously.
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Old 05-06-2013, 11:21 PM   #435
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Nitro Dan, and anyone else watching, here is some pictures showing what I was describing

You can see I fully welded this piece before I put the collector on, ie, no internal welding.















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Old 05-07-2013, 08:26 AM   #436
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Quote:
Originally Posted by thenuge26 View Post
You aren't getting any scavenging on a turbo car. That's how the turbo works, the pressure in the manifold is greater than the pressure in the downpipe. The turbine ruins any scavenging effect.

Equal length is good because the pulses will arrive simultaneously.
But you still loose exhaust gas energy in a merge like that, and thats whats important. When you cram them all in like that they loose a lot of velocity which is part of the energy equation, it doesnt have as big of an effect as heat or pressure to turbine energy but its in there.
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Old 05-07-2013, 07:19 PM   #437
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"loose" != "lose"
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Old 05-07-2013, 07:24 PM   #438
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Boost I know nothing about headers, but that one is gorgeous. It's sad that its not for a miata engine. I'm hoping V8 in one though?
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Old 05-07-2013, 08:38 PM   #439
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Boost I know nothing about headers, but that one is gorgeous. It's sad that its not for a miata engine. I'm hoping V8 in one though?
Nah, not a miata unfortunately.
I'm contemplating a miata with a 1uzfe with itbs, a true 4-2-1 180* header system with an x pipe, and a dry sump so I can cross the tubes under the engine. It would have a glorious sound like that of an f430 or better, with I'm guessing at least 350whp on an un-opened engine. Should be the hell of a car if I ever do it.
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Old 05-07-2013, 09:12 PM   #440
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Holy crap, that is some gorgeous work on that header. Mad props.
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