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Old 01-23-2007, 02:36 PM   #1
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Default tubular turbo manifold design

Got a question...

What's the story on runner diameter for a equal length tube tuned turbo header? I did some quicky calcs and the perimeter of the ports suggest a 1.5-1.6 inside diameter pipe for matching size (if you squish it down to match the port).

But what's the ideal diameter in general?

Is there a magic "manifold internal volume" to stay under? a max diameter for high velocity flow? a minimum for avoiding choked flow?

what about length? short is better, but how long is too long?

grassy ***,

Matt
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Old 01-23-2007, 03:08 PM   #2
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Generally what I have seen and use is 1.5" Sch. 10/40 tubing which is approx 1.5" id and 1.9" od. The best flowing manifold are usually a bit longer with low divergent angles into the collector.
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Old 01-23-2007, 03:39 PM   #3
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hmm ok.

I usually see the four pipes merge at the collector by being mitered together... like a four leaf clover.

Mcmaster has some neat offset transitions that might be interesting.... what's the hole size on the T2 flange?
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Old 01-23-2007, 03:52 PM   #4
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Right, I was referring to the angle at which they are mitered being a smaller angle.
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Old 01-23-2007, 04:19 PM   #5
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Here's what I was talking about...



they have them in
1 1/4" x 1/2"
1 1/4" x 3/4"
1 1/4" x 1"
1 1/2" x 1/2"
1 1/2" x 3/4"
1 1/2" x 1"
1 1/2" x 1 1/4"

sizes. they also have center-center transitions. maybe if you wanted to use a flattened tube at the port and downsize to a smaller runner size.
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Old 01-23-2007, 05:08 PM   #6
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cha-ching.
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Old 01-23-2007, 05:13 PM   #7
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why, because they're 30 bucks each?
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Old 01-24-2007, 09:32 AM   #8
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Yep. $30 is gas for 3 days.

I believe 1.5" sch.40 pipe fits pretty well on a T2 inlet flange. I just did this a few weeks ago and can check what size pipe it is later today. I did have to use a torch and massage it a little.
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Old 01-24-2007, 10:03 AM   #9
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Interestingly enough, gas for 3 days is what you get after eating $30 worth of Taco Bell food.

Why do people relate everything to the price of gas nowadays? It's like those fast-food commercials were people relate everything to the price of frostys or jr. bacon cheeseburgers or whatever. $1 million!? That's like a million junior cheeseburgers!

Sorry to get sidetracked
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Old 01-24-2007, 10:03 AM   #10
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You're talking about using four of those to make a collector?

$30 in 3 days? That's a lot of driving... or a lot of full throttle driving!
I think the gas vs. whatever is just significant of how much people drive. I've driven less than 1000 miles since October.
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Old 01-24-2007, 10:26 AM   #11
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I don't even use miles as a measurement of distance anymore...I just use dollars-worth-of gallons.

"How many miles do you have on your car?"

"About $12,500 worth of gas."
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Old 01-24-2007, 10:42 AM   #12
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For some reason when he said gas... I thought welding gas. Heh
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Old 01-24-2007, 11:02 AM   #13
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ok thread hijackers. I dont give a rats *** about gas prices. If I did I'd drive a turbo prius.

I'm not actually *making* this manifold yet, I'm just pickin your brains. I saw those offset flares on McMaster.com and thought they'd make a nice smooth collector.

I'm tempted to draw some stuff up in pro/e and verify centerline distances are within a percent or two for my own edification.

I just thought I'd get the DIY expert opinion first.
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Old 01-24-2007, 11:21 AM   #14
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Ohh making your manifold in pro E or the like is a great idea. I did that with my twinturbo manifold and created full scale templates for all the transitions. It made life a lot easier.

You do have a good idea, using one of the larger transitions maybe 2.5 - 1.5 may make the collector fab work a lot easier. I would consider it especially if you are using a MIG welder so you can fill in any gaps.

One area I have used transitions is on my downpipe. Burns Stainless has nice high quality stainless transitions in regular exhaust pipe thickness; I used a 3" to 2.5" on my old Downpipe.

Back to the original hijack: I drive just over 60 miles each direction to work, which I think is average for this area. The guy I carpool with drives from center city Philadelphia to the Jersey shore each day.
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Old 01-24-2007, 01:04 PM   #15
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modeling els as I type

I didn't think of a large 4-into-1 sized transition... but wouldn't that be much harder to deal with than just making up a flat-walled funnel shape? four circles dont really fit well in a big circle (or a square for that matter).

I did the downpipe transition too. My new DP will have a 2.25-3 transition since the 2876 output is 2.25 at the flange.

that's a long drive. I used to do 45 miles each way around silicon valley... long commute and most expensive gas around sucked... but I carpooled--more for wear and tear on the miata than anything else.
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Old 01-24-2007, 01:25 PM   #16
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Found this secret link of flange sizes. neat.

http://www.jgstools.com/turbo/tif.html
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Old 01-24-2007, 02:23 PM   #17
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Four circles do fit well if your cut them right.
http://www.homemadeturbo.com/forum/i...2899#msg352899
That link has a good write up on making your own collector.
Beware, it's in the Fabrication/**** Subforum.
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Old 01-24-2007, 03:58 PM   #18
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fabrication/****. heh.

that's how my manifold's built. but damn, spend a little on a TIG welder and you get nice welds after some practice.
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Old 01-24-2007, 04:06 PM   #19
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Flipside has head flanges available that have the recess machined already for the 1.5" Sch 40.
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Old 01-24-2007, 05:11 PM   #20
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could flipside have anymore media on their main page? geezes.
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