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Piping diameter for exhaust manifold

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Old 05-10-02, 07:44 PM
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Question Piping diameter for exhaust manifold

Is 2.5" I.D. piping too large for a street ported 13brew using a T66 with a P trim turbine wheel and a 1.15 a/r ? , also is there any specific place to locate the take off points for the wastegates ? (closer to the exhaust port , closer to the inlet to the turbo or it doesn't matter?).
Old 05-10-02, 09:30 PM
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2inch, if you aren't running exhuast port sleeves - use a short section of 2 1/2 and taper it back to 2 inch
Old 05-10-02, 10:13 PM
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I used 2" stainless tube for the manifold to turbo, and then 1.5 inch for the wastegate.
The exhaust port is pretty much 2" exactly, upping to a pipe larger than the exhaust port size would just drop velocity, I would think, but I could be wrong..
Here is my manifold in stainless I built, its for my TII..Max

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Old 05-10-02, 10:33 PM
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Originally posted by Maxthe7man
I used 2" stainless tube for the manifold to turbo, and then 1.5 inch for the wastegate.
The exhaust port is pretty much 2" exactly, upping to a pipe larger than the exhaust port size would just drop velocity, I would think, but I could be wrong..
Here is my manifold in stainless I built, its for my TII..Max

Looks good.
Old 05-10-02, 10:35 PM
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Originally posted by Maxthe7man
I used 2" stainless tube for the manifold to turbo, and then 1.5 inch for the wastegate.
The exhaust port is pretty much 2" exactly, upping to a pipe larger than the exhaust port size would just drop velocity, I would think, but I could be wrong..
Here is my manifold in stainless I built, its for my TII..Max
Yeah, I think that I remember from a compressible fluid dynamics course that if a flow is travelling less than the speed of sound then going from a larger opening to a smaller opening will lead to an increase in velocity. That's why they use velocity stacks on throttle bodies. The opposite holds true for speeds greater than the speed of sound.
Old 05-12-02, 11:45 AM
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I just applied what I was taught in tradeschool, big pipes low velocity, smaller pipes higher velocity, although there is to small as well, thats when capacity becomes a concern.. I was reading a bit through some old books I have, and there is a maximum exhaust pipe size as well, I know in C. Bell's book, he says there is no maximum to a turbo charged cars exhaust size, but another book I have states that if the gas drops to much velocity it will start to hurt overall flow, and there is the problem also of moisture condensing in the exhaust system which oxidizes the pipes, and fills low spots with water..
I polished the manifold a bit last night, it looks super sweet now.. I just hope it works ok....
I built one out of mild steel before which was ok, its usable but its not near as nice as the stainless one, and TIG welding is far prettier than the ole AC buzz box welding...
Old 05-12-02, 11:53 AM
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Originally posted by Maxthe7man
I just applied what I was taught in tradeschool, big pipes low velocity, smaller pipes higher velocity, although there is to small as well, thats when capacity becomes a concern.. I was reading a bit through some old books I have, and there is a maximum exhaust pipe size as well, I know in C. Bell's book, he says there is no maximum to a turbo charged cars exhaust size, but another book I have states that if the gas drops to much velocity it will start to hurt overall flow, and there is the problem also of moisture condensing in the exhaust system which oxidizes the pipes, and fills low spots with water..
I polished the manifold a bit last night, it looks super sweet now.. I just hope it works ok....
I built one out of mild steel before which was ok, its usable but its not near as nice as the stainless one, and TIG welding is far prettier than the ole AC buzz box welding...
How did the mild steel manifold work out when you used it?
Old 05-12-02, 12:34 PM
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I made the mild steel one, never ever used it on the car though, its sitting under my workbench collecting dust, I may put it on my N/a if I find another cheap T04 or something.. I know some people who have had concerns about mild steel, however I used XH weld els, which are about a 1/4" thick wall, they would take rotary heat no problem, I use them at work for piping hipressure ammonia systems that go from -30f to 280 f and back again at the flick of a switch with 200 psi on them, they never crack, break deform or anything like that, I would not hesitate to use mild steel of this kind anywhere..
I know some people have used some real thin wall cheesey tubing for headers and manifolds and it does not take well to the abuse, but 1/4 wall stuff is tough beyond belief...
There has been some suggestion about Inconel and more exotic materials, I cannot at this time though justify the cost of such stuff..
I built a header out of food grade stainless last year on my n/a, it wasn't even tig welded, it was mig'd and stick'd together, its holding up fine even though it glows red like a stove element after a hard run.. no cracks, nothing...Max
Old 05-12-02, 01:47 PM
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Originally posted by Maxthe7man
I made the mild steel one, never ever used it on the car though, its sitting under my workbench collecting dust, I may put it on my N/a if I find another cheap T04 or something.. I know some people who have had concerns about mild steel, however I used XH weld els, which are about a 1/4" thick wall, they would take rotary heat no problem, I use them at work for piping hipressure ammonia systems that go from -30f to 280 f and back again at the flick of a switch with 200 psi on them, they never crack, break deform or anything like that, I would not hesitate to use mild steel of this kind anywhere..
I know some people have used some real thin wall cheesey tubing for headers and manifolds and it does not take well to the abuse, but 1/4 wall stuff is tough beyond belief...
There has been some suggestion about Inconel and more exotic materials, I cannot at this time though justify the cost of such stuff..
I built a header out of food grade stainless last year on my n/a, it wasn't even tig welded, it was mig'd and stick'd together, its holding up fine even though it glows red like a stove element after a hard run.. no cracks, nothing...Max
Yeah, I figured that 1/4" would be fine. Thanks for the information.
Old 05-13-02, 01:42 PM
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Is 2.5" I.D. piping too large for a street ported 13brew
2.5" id piping for the primaries? I've never even heard of anyone using piping that big. Even on methanol.
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