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Velocity stack on the intake?

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Silver3Tiger

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Discussion starter · #1 ·
I was looking around at intake manifolds and see from $900-200. My questions are..

For a turbo motor are Velocity stack really needed(larger rounded edges)? Yes I know for non-turbos they are great. I have had a few toys with different length stacks.

As the turbo is pushing the air in instaed of pulling. I can see a little benefit to having some radius edges yet not really.

Would like to have others input
Thanks

S.T.
 
#3 ·
Velocity stacks arent for turbulence, they are there to promote better entrance into a port. 99.9% of what the people on this board will tell you about velocity stacks is heresay. Honestly I imagine it does introduce a better entrance coefficient into the runner which would promote better airflow. The terms push and pull show me that you are looking at it completely wrong. Both scenarios should be taken from an absolute pressure perspective, in which case both scenarios look identical; higher pressure in the plenum leading to a lower pressure in the runner.
 
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#5 ·
In some manifolds it doesnt help. My manifold has them built into the runners to promote airflow and compression of the air. (its a bj's btw) But on some other manifolds where the stacks are not made into the runners, i would figure it would do more bad then good due to the turbulance underneath them.
 
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#6 ·
1QuickChic said:
In some manifolds it doesnt help. My manifold has them built into the runners to promote airflow and compression of the air. (its a bj's btw) But on some other manifolds where the stacks are not made into the runners, i would figure it would do more bad then good due to the turbulance underneath them.
Click to expand...
id love to have bj's mani or even a head... lol

swade
 
Discussion starter · #7 ·
When looking at different manifolds there are many sizes for the velocity stacks. I understand the runners need to be one size for the intake for the head. My questions are then...

Has any one don't any research on the radius of the stack for better air flow? Like magnus(think thats right) have larger stacks and bj's seem to have smaller ones. I know that carb. cars have larger roll overs on the velocity stacks.

Is there a benefit to have a larger area on the manifold(above the runners)?

Thanks

S.T.
 
#8 ·
I know BJ did a lot of math in making his manifold and quite a bit of test benching, on his manifold. And from what i understand it has no cap on the airflow it can funnel.
 
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#11 · (Edited)
When did BJ ever put velocity stacks in his intake manifold? Could you send me a pic of that. I've got a BJ's on my car and I use to go to his shop in Tulsa alot before he went a-wall and never seen him putting v-stacks in any of them. Are you just referrinng to the way the runners have a curved edged at the top as opposed to a 90 degree turned from where the plenum meets the runner?
 
#13 ·
that's kinda what I thought you meant. I was just editing my post to include the last statement. I was just making sure you didn't have big as v-stacks in them like the old Victory performance did. (I think it was Victory that I first seen that on.)
 
#14 ·
No no no, I dont understand those designs and after seeing mine built and tested, I wouldnt have any other manifold then bj's. Glad I got one before he went bye bye.
 
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Discussion starter · #16 ·
If Bj's is out of businss who is the next manifold maker to look for?
I did forget to say my plan is to build a 2.4 with a Gt30r turbo.
This also bring a question to mind, TB's? I just had steve do my TB to a 63mm( Great work). What would be the best set up for TB? 75,80,....?

S.T.
 
#19 ·
1. I've heard that some ram air systems don't work because if you try and force a large volume of air into a cylinder head or intake manifold that can't evacuate it fast enough a cushion of air will form and impede the flow. Has anyone else heard of this. And maybe this is a stupid question but how does it not apply to a forced induction engine?

2. Why does the bellmouth have to extend up out of the runner and into the plenum, couldn't the same be achieved with runners of equal legnths but a bellmouth flush with the floor of the plenum?
 
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