Whats the benefit to having the velocity stacks raised off of the plenums floor then
having them flush with the floor?

 

Its amazing all the technology that Porsche uses in there engines!

The raised Velocity Stacks Help with straighting the air and increasing velocity!

I know it does not look right, but it really works....

Eric

 

Its my understanding that the air directly against the walls of the plenum is rather stagnant for lack of a better term. Raising the velocity stacks off the floor of the plenum puts them back into a healthy airstream and as stated helps straighten out airflow.

 

There is more air available at the inlet when it is raised off the floor.

The raised port can pull air from BELOW the entry level. The Floor based port can only pull air from above the entry. More surface area is exposed to the inlet.

 

the word you guys were searching for is Laminar flow. but Im going to have to agree with 99 GS-T

 

Anybody want to guess on what the runner length of those intake ports are?

Look pretty long. Not to mention the valve angle looks VERY shallow and the port angle is looking to be almost 45 degrees to the head surface. That's sexy...

 

"LAMINAR" "is when gas or fluid seems well organized" well its not realy the fact of wether its flat againts or not they are just mainly tuning the path of the air flow for this application but yes raising them does gather a more oraganized collection of air but the manifold has to be deisigned in conjunction with the stacks to minimizes tumbling and pulses or pressure waves and also runner length obviously is prolly the main issue in that engine do to engine compartment constraints most likely just my 2 pennies

 

if you "read" what I wrote...you'll notice I simply filled in their blank. I was not suggesting that "laminar" flow was the reason. I know what laminar flow is...Im doing Ad lab research on laminar flow, reynolds number, max flow, average flow, turbulent flow, etc...fluid dynamics :-P my 3 cents...because I give more than most.

 

The reason velocity stacks are raised above the floor is to get them out of the boundary layer. The boundary layer does have a little to do with laminar and turbulent flow, but what is really important is the flow velocity at any point in the pipe.

It is difficult to figure out what is going on in a pipe with flow. But we do know one thing: Because of friction, the flow velocity at the wall is zero. So the velocity distribution across a pipe must be zero at the walls and increasing in some function toward the center of the pipe, such that the maximum flow velocity occurs at the center of the pipe.

Would you rather put the velocity stack in the part of the pipe that has zero flow velocity, so that it has to speed up to get into the stack, or would you rather put it where a large flow velocity already exists?

 

Thanks.