Critique this Intake Manifold - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-25-2009, 10:54 PM   #21
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I'd think there'd be more chance of starvation in a tubular IM design. Plus the runner length would cause major restriction for top-end flow. The ideal of the plenum is to have all the plenty of available airflow on tap within the plenum to feed the runners.
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Old 11-25-2009, 10:58 PM   #22
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Quote:
Originally Posted by ftjandra View Post
Anybody have access to a flowbench for free/cheap?

--Ferdi
I do, but not all the time. And I'd have to learn how to get flow numbers on it, which wouldn't be hard.
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Old 11-25-2009, 11:05 PM   #23
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Dyno it. Even CFD numbers are worth little, like brain said flow/pressure in each primary (short!) is in waves. Takes software way beyond what any of us have to even come close to modeling it accurately. Best way is to dyno it and determine for yourself it the gains were worth the cost.
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Old 11-25-2009, 11:09 PM   #24
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Flow numbers would help give you an idea of if you're completely ******* up or not though. Like someone said in another thread regarding IM design, you could easily melt an engine by messing with this. Not to say the guy making this sucks...but it could help.
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Old 11-25-2009, 11:18 PM   #25
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True.

I've seen some physiclly very similar intakes do some VERY different things on the same engine. This is with V8 stuff which may have more going.
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Old 11-25-2009, 11:20 PM   #26
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Quote:
Originally Posted by TurboTim View Post
True.

I've seen some physiclly very similar intakes do some VERY different things on the same engine. This is with V8 stuff which may have more going.
Yep, airflow pretty much has a mind of its own. Does some weird ****...
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Old 11-25-2009, 11:23 PM   #27
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Quote:
Originally Posted by Jeff_Ciesielski View Post
Toyota does it on some of their corolla engines.

[IMG]http://www.tercelreference.com/tercel_info/component_library/4efe_tubular_intake_manifold_1.jpg[IMG]

Edit: Looking at it, this faces the proper direction to have the flange cut off and a b6/bp flange welded on.... Only problem would be clearing the shelf/shock tower.
That manifolds main objective is to increase/optimize low end and midrange torque. The opposite of what big turbo miata guys are trying to do, which is improve airflow up top.
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Old 11-25-2009, 11:24 PM   #28
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An Evo tuner who said "******" ever 3-words told me that a huge chamber with long runners and 360* horns that portrude deep into the plenum will make the most torque...and to shorten them to add horsepower.
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Old 11-25-2009, 11:26 PM   #29
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Quote:
Originally Posted by MartinezA92 View Post
I do, but not all the time. And I'd have to learn how to get flow numbers on it, which wouldn't be hard.
Free? And, is/has the setup to test Miata intake manifolds? I wouldn't mind sending you my manifold to get tested. My car is down right now anyways.

Mine is for the BP4W head, but with the throttle body on the opposite side (Protege).

--Ferdi
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Old 11-25-2009, 11:28 PM   #30
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Quote:
Originally Posted by hustler View Post
An Evo tuner who said "******" ever 3-words told me that a huge chamber with long runners and 360* horns that portrude deep into the plenum will make the most torque...and to shorten them to add horsepower.
Shorter and wider, or just shorter? As far as I know, and I may be wrong, longer smaller runners increase velocity for low end power at the expense of overall flow and wider, shorter runners would increase flow at the top end. Making them just shorter seems like it wouldn't do anything.
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Old 11-25-2009, 11:30 PM   #31
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Quote:
Originally Posted by ftjandra View Post
Free? And, is/has the setup to test Miata intake manifolds? I wouldn't mind sending you my manifold to get tested. My car is down right now anyways.

Mine is for the BP4W head, but with the throttle body on the opposite side (Protege).

--Ferdi
Free, but we don't have a specific set up for a Miata intake manifold. I'm not an airflow tester expert, but couldn't you just bolt it up to a Miata head and test it that way?
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Old 11-25-2009, 11:31 PM   #32
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so in other words you want pretty much 0 runners with a lot of empty space as a plenum?
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Old 11-25-2009, 11:32 PM   #33
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i agree that the runners look super short. i did alot of research on dynamic flow effect, creating the optimum runner length to catch the intake pulses and actualy create power off them. i have raise velocity stacks in my manifold, that also helps alot with the air flow. from what i read you want the stacks to be about 1"-1.5" off the plenum floor. i cant say much about cyliner 1 being starved for air. the only way to fix this is to change the plenum shape, and make the throttle body entrance as far away from cyl one as possible.

this is my manifold
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Old 11-25-2009, 11:34 PM   #34
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how about mounting the throttle body up top or the side and making both ends same shape?
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Old 11-25-2009, 11:35 PM   #35
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As discussed in previous thread: that opens up a can of fitment worms
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Old 11-25-2009, 11:36 PM   #36
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if you make the runners quite short, whats the problem?
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Old 11-25-2009, 11:42 PM   #37
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up top won't work because of hood.
to the side the piping coming in from the front would have to make a big *** loop or sharp bend. Not to mention some other problems.

Just my .02 but I think if there was any merit to that idea some aftermarket manifolds would already have been made that way. I don't see any like that. Even on other cars.
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Old 11-25-2009, 11:43 PM   #38
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I'm curious what effect having the air inlets raised off the surface off the plenum has. It would seem like you'd want the inlets of the runners to be flush with the surface to allow the full volume of the plenum to flow smoothly into the runner, but maybe the length of the runners supercedes that concern?

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Old 11-25-2009, 11:44 PM   #39
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I'm very curious about the same thing.

I noticed that expensive supercars such as ferrari and audi and others have it this way too:


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Old 11-25-2009, 11:44 PM   #40
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the effective rpm of the manifold is sky high, it wouldnt be optimum for the engine. the way it works is when the intake valve opens the engine sucks in a big gulp of air, when the valve shuts, the incoming air slams into the back of it and bounces off. creating a pulse, now this pulse bounces back and forth in the intake track loosing momentum evey time it changes directions until the valve opens again. it is possible to tune the runner length to time the the pulse so that it bounces once or twice and hits the valve as it opens again creating a ram air effect know as "dynamic flow effect" this increases the engines VE, making more power for a given rpm range.
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