Intake Manifold Design Question

[adrianpike]

What do you guys think about internal velocity stacks inside a custom intake manifold plenum? Should I make them flush with the plenum wall, or inset a little bit, and if so, how much?

 

[Jostyrostelli]

Re: Intake Manifold Design Question

What do you guys think about internal velocity stacks inside a cistom intake manifold plenum? Should I make them flush with the plenum wall, or inset a little but, and if so, how much?

Sorry, these are the words I don't understand...I'd like to discuss but don't know about what :lol:

 

[adrianpike]

Whoops, sorry for the spelling pistakes. Fixed now.

 

[The_Finn]

i think you would want them flush with the wall of the pelnum... if they are inset it's just more distance for the air to travel in the runners... i was always under the impression the whole point of velocity stacks were to get rid of the pelnum all together.... provided you have individual TBs they just smooth out the airflow going into the engine... if your keeping the pelnum the most important part is equal length runners and a pelnum design that equalizes airflow to all the runners...

but i could be wrong on all these points

TF

 

[adrianpike]

This is for a boosted application, so a plenum will be required.
Perhaps I've mis-spoke when I said "Velocity Stacks". What I mean, is a radiused entry from the plenum into the runners, which decrease somewhat in radius along their length, to increase the velocity of the incoming air.

Initially, I believed in making them flush with the plenum wall, but I saw many high-po builders making them somewhat inset. I believe that this is to retain runner length for an accoustic ramming function, and to move the plenum inward a bit for packaging reasons. What I'm not sure about, though, is just how much of an inset pertains to how much of a negligible reduction in flow.

Accoustic ramming effect:
L = (K*C) / N
Where:
L=length of pipe in inches (sorry, I know us Americans are f'ed up for still using that damn system... )
K=constant (Chrysler claims it to be 72, Philip Smith says 90)
C=velocity of sound in feet/second
N=rpm

Chrysler also gives a fuzziness factor of +- 3 inches for runner length. Nonetheless, longer runners are better.

The issues with longer runners and throttle response are moot, as spoolup will be plenty fast for some disgusting fun.

 

[Leppy]

Not sure if I am correct with this (for turbo apps), but aren't longer runners only better at lower rpm?

When an engine is at low rpm you want the air flowing as fast as possible but when at higher rpm you want as much air as possible.

Ford came out with the variable length air intake a while back on their Falcons.

But as I said. I'm not too sure about turbo applications with this.

 

[Jostyrostelli]

Wow, anybody willing enough to explain what you are talking about?
Or have a link to some explaination..would like to know more about this..

Oh btw, I still can't read (understand) it now you've corrected the typos

 

[The_Finn]

ok i will give it a try

Velocity stacks as i was talking about them are used instead of a whole maifold they compress + speed up the air going into the engine because they are taperd like little trumpets obviously you need individual throttle bodies and you can't have forced induction...

a intake manifold is a bunch of different parts...

the big chamber up top is the pelnum and it is supposed to equalize pressure to the runners (the 4 small pipes that go from the pelnum to the actual intake valves in the picture)

adrian wanted to know which was a better idea for incorperating velocity stack like design into his runners if he should have the runners start to taper in directly from the pelnum chamber or if the runner should be straight for a bit then begin to taper in

i hope that helped

TF

 

[Jostyrostelli]

Okey thanks, so most of the parts I already knew, I'll try to google more stuff.