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Old 02-05-2018, 01:59 PM   #1
mikep
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Default Intake Manifold Plenum Design: Stubs or holes?

Inside a home-built plenum:

Stubs of tube, insides contoured (outer edges sharp)?

Stubs rounded inside and out?

No stubs, just holes into individual runners?

The stubs would be the sawed-off remnants of a 280ZX Nissan manifold.





I wonder if stubs, allowing air to flow past on the outside, will flow smoother the a wall with holes.
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Old 02-05-2018, 02:14 PM   #2
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Can you not get some stacks or bellmouths on those stubs?
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Old 02-05-2018, 02:19 PM   #3
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Depending on the amount of material you have to work with, you could weld the tubes to a plate and take a router to round over the holes/welds making a velocity stack of sorts.
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Old 02-05-2018, 02:41 PM   #4
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There is a Z fuel injected manifold without all that EGR stuff. Not sure what year, but I've seen it. I gotta buddie who has 30 plus Z's he's parting out.
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Old 02-05-2018, 03:49 PM   #5
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There is only one way to do it. Radius the inlet, from a flat plate is easy to do.
Sharp edges cause turbulence and restrict airflow.

I refer you to D Vizard


A good example scrounged from the net:
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Old 02-05-2018, 04:04 PM   #6
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That would be the holes version I was describing.

The velocity stacks version would be the other (stubs) version with sharp outer edges.
Velocity stacks is what I would think flows the most, but does it?
I remember head bench testing where a half-round at the entrance flowed better. But I have no copy of the article.

I have limited space now, but will have more when I get rid of the struts in 2 years with a different suspension.
End-goal if possible is a plenum to receive an M90 supercharger from a T-Bird.
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Old 02-05-2018, 04:06 PM   #7
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book excerpt on clay radius on a port

https://books.google.com/books?id=z7...inlets&f=false
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Old 02-05-2018, 04:13 PM   #8
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According to this, it's only a 1% difference.

https://www.performancebyie.com/blog...ght-bellmouth/

It's from a group selling something, and they only did a computer simulation.
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Old 02-05-2018, 05:47 PM   #9
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Doesn't GM have an 8 hole manifold that fits on one of their l s motors?
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Old 02-05-2018, 11:53 PM   #10
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Stubs or holes? Male/female? Why would it matter what gender a manifold is?

That joke aside, velocity stacks and radii help with an n/a engine, this is undoubtedly proven. Especially if you tune the intake to take advantage of the inversion wave. However, there is a lot of debate out there about whether there is benefit in a boosted engine. I am under the impression that the radius will help increase velocity and flow by smoothing the transition, but velocity stack length on a boosted engine wont make much difference. Well, 20 foot long intake runners(Bosuzoku ftw.) will effect throttle response but not flow.

Last edited by NotSoFresh; 02-06-2018 at 12:06 AM..
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Old 02-06-2018, 09:40 AM   #11
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Quote:
There is only one way to do it. Radius the inlet, from a flat plate is easy to do.
Sharp edges cause turbulence and restrict airflow.

I refer you to D Vizard
Any reference to David Vizard concludes the conversation.
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Old 02-06-2018, 01:42 PM   #12
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Quote:
Originally Posted by NotSoFresh View Post
That joke aside, velocity stacks and radii help with an n/a engine, this is undoubtedly proven. Especially if you tune the intake to take advantage of the inversion wave.
I tend to agree, but I need to find out if there is a more than 1% difference.
Personally, if I cut off at the green lines and weld the plate there, I will have clearance probs. If I try to turn those into stacks, the curves will make it hard to get a plate slide over far.
And if I shorten the cutoff lengths, I will have to run studs and nuts (I'm ok with that)

If I start from scratch, who knows.

I'm not interested in using any nissan intake. And I'm only going to inject it if I go with the supercharger or a turbo.
The SUs are going on there for now.
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Old 02-06-2018, 01:42 PM   #13
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Thanks for the comments.
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Old 02-10-2018, 08:25 PM   #14
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you would need a Dyno to find out look at the millions of different manifold designs, i would think the ram tuning would depend on what r.p.m. you would be running
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Old 02-13-2018, 09:35 PM   #15
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Nope. Building this once.
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