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Old 07-25-2005, 02:12 AM   #1
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Default Anyone know any good TB size articles?

I'm trying to understand why a certian size TB would be too big on an n/a application.
I know velocity is key on an n/a motor and that you can only flow so much given your current setup.
I was thinking about possibly going to a north* TB some time down the line but i just keep remembering things i read like 'its too big', 'you'll never flow that much' or the straw comparison when hector'* 3" CAI'* came out.
I want to understand it better.
I googled for some articles but none really went far enough into the explination.
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Old 07-25-2005, 11:34 PM   #2
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I would talk to INTENSE and ZZP and see what they think about your current setup and whether it is necessary or not. You could also go over to the GP forum and see what people with your setup do. Nobody here has modded a NA engine to the level where you are right now. I would think that you only need a larger TB when it is the smallest point in your intake/exhaust path.
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Old 07-26-2005, 10:53 AM   #3
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your best bet would be to look up some fluid dynamics stuff... around the lines of laminar flow and the reynold'* number... it should help you understand.

basically, the reynold'* number can be used to tell you if your fluid flow is laminar or turbulent (or transitional for that matter). it'* based on several variables, including the dynamic viscocity of the fluid (air, in your case), the velocity, the density of the fluid, and the diameter of the pipe.

by using a TB (or intake pipe) that'* not the right size, you can introduce turbulent flow. w/o looking at any actual numbers, it'* hard to say what size TB would be ideal.

the eq for the reynold'* number is...

R = (density of fluid * velocity * pipe diameter (in your case)) / dynamic viscocity

Re < 2300 = laminar flow
2300 > Re > 4000 = transitional
Re > 4000 = turbulent

So basically, each setup is a little different... and you can have a TB that'* too big, or one that'* too small...
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Old 07-26-2005, 01:58 PM   #4
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Quote:
Originally Posted by mkaake
your best bet would be to look up some fluid dynamics stuff... around the lines of laminar flow and the reynold'* number... it should help you understand.

basically, the reynold'* number can be used to tell you if your fluid flow is laminar or turbulent (or transitional for that matter). it'* based on several variables, including the dynamic viscocity of the fluid (air, in your case), the velocity, the density of the fluid, and the diameter of the pipe.

by using a TB (or intake pipe) that'* not the right size, you can introduce turbulent flow. w/o looking at any actual numbers, it'* hard to say what size TB would be ideal.

the eq for the reynold'* number is...

R = (density of fluid * velocity * pipe diameter (in your case)) / dynamic viscocity

Re < 2300 = laminar flow
2300 > Re > 4000 = transitional
Re > 4000 = turbulent

So basically, each setup is a little different... and you can have a TB that'* too big, or one that'* too small...
I'm very familiar what all the above mentioned. I learned that and much more in my fluids class last semester.
I know that size transition will slow down the flow among other things. I wasn't going to have a 75mm throttlebody with a 69mmx80mm (guess at L36 UIM entrance) opening. When i installed my L67 throttlebody, i epoxied the coolant holes, ported the exit to mimic the exit on the L36 so it will match up with the L36 UIM( less turbulance), and i removed the MAF screen and smoothed out the slot for the screen.
----
What i am trying to understand more is how you could have a throttle body with too much cfm in an n/a application and how do you guess the optimum cfm without dyno tests. What'* the principle behind it?
----
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Old 07-26-2005, 03:45 PM   #5
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ahh, I see.

I don't think you can have a TB with too much CFM in an n/a gettup... surely you could introduce turbulence, but since the motor is going to pull through what it'* going to pull through, I don't see how a TB could be too big in that sense.

so in short, if there'* some reason out there other than turbulence, i'd be interested in hearing it too...
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Old 07-26-2005, 03:46 PM   #6
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p.*.

where do you go to school?
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Old 07-26-2005, 04:34 PM   #7
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I'm a M.E. major at Temple University. We rival Drexel which has a pretty big rep for engineering in the area. I have had a few teachers that previously taught at Drexel that prefer Temple'* curriculum though. I think it'* a good school but that'* a pretty biased opinion.
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Old 07-27-2005, 02:09 AM   #8
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so basically the turbulence doesnt matter since the air will have to change directions a couple times before it is used anyway.

Wouldnt the only reason to upgrade the TB be if you had a maxed MAF sensor? Otherwise your TB should be under the max, correct?
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Old 07-27-2005, 10:50 AM   #9
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Quote:
Originally Posted by macho_mike21
so basically the turbulence doesnt matter since the air will have to change directions a couple times before it is used anyway.
Turbulence does matter. Just think about how everyone port matches everything.
Quote:
Originally Posted by macho_mike21
Wouldnt the only reason to upgrade the TB be if you had a maxed MAF sensor? Otherwise your TB should be under the max, correct?
That'* what i've read before too. But why wouldn't a larger TB or one with more cfm still help? Another thing is could a n/a 3.8 really even max out the stock maf?
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Old 07-27-2005, 01:29 PM   #10
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I don't think that you'd ever overload the stock maf - mainly because with the n/a application, you're never going to be compressing your air like you do with a boosted application. we can do all we want to make it flow more freely, and flow faster, but at the end of the day, there is a practical limit that can be reached by a motor that displaces a finite volume at a finite speed...

so I guess the question is just how much can our MAF take? I'm guessing that the turbo L36 projects out there are using the L36 TB (or at least one of them), so as long as the maf can take a boosted application, we shouldn't have any need to worry about it not handling the most free flowing L36 imagineable...

this is all, of course, just thinking out loud, but I don't see any reason that our thinking to this point is flawed...
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