Intake plenum theory

[andrew_mx83]

hmmm thanks for the info ed

unfortunately mine fairly simple, the standard 7m manifold is in 2 parts. i am leaving the bottom half which gives me 6 x 45mm runners in a row with a nice mounting flange.
the plenum is then the rectanlge section described above with the 6 ports drilled into it which will be bolted onto that stocky manifold. will do some work with the dremel to make a bit of a bellmouth into each runner but otherwise its fairly simple -this is just a stopgap measure to get the motor back in the car while i fuck around getting the triples setup (more work than i have time for atm)


btw, whats with the "balance pipe" on the uz plenum? i thought v8's only needed that on the exhaust?

[Draven]

re: balance pipe... I'm guessing that's for a FI setup? Otherwise I can't really imagine the point.

[timbosaurus]

So Ed, technically, what is wrong with that one? ^^^

You say you don't like round tubes, so I guess that could be it. And it's also a fairly small volume. Anything else?

I'll be making one for a 1G, I was thinking bellmouthed intake tubes, with the ends sitting 0.5" out from a 6mm flat plate (~125mm wide x 550mm long with semicircle ends).

The 'cover' would then be a two 5" bends, cut in half radially, half a 5" tube (that would probably actaully be angled slightly away from the engine) and a flat sheet to fill in the gap.

      ______________________________
    /        |         half tube          /            |
  /        _|_________________/          __|
/ bend /          flat sheet        / bend /               
|_____|__________________|_____|
  |   |    |   |    |   |    |   |    |   |    |   |
  |__|    |__|   |__|   |__|    |__|   |__|

What is the general opinion of this idea?

[eeeyan]

sounds ok but your drawing is fail.

[ed]

re: balance pipe... I'm guessing that's for a FI setup? Otherwise I can't really imagine the point.

balance pipe... technically on cross plane v8 the intake pulses per bank are unbalanced, so they should either have a common plenum, or a large x-over. i dont think that small bit of pipe would do much, even though that was the original idea. stolen from the top secret 350z i think.

[Duk]

balance pipe... technically on cross plane v8 the intake pulses per bank are unbalanced, so they should either have a common plenum, or a large x-over. i dont think that small bit of pipe would do much, even though that was the original idea. stolen from the top secret 350z i think.

But any decent V6 engine uses equal left-right firing. Basically 2, 3 cylinder engines on a common crankshaft.
Would an equal left-right firing V6 bennefit from seperate plenums that are linked together at the opposite end of the throttle bodies? Maybe equipped with an internal valve that gets opened at a given point to change the manifold characteristics?
Or even a dual plenums on a straight 6, that have runners that joint to cylinders that are equal firing orders appart, that also link together at some point in the rev range?

[timbosaurus]

sounds ok but your drawing is fail.

awww, c'mon! It's the best I could do on my work laptop!

This is the sort of thing I'm thinking. Shouldn't be too hard to fab up, would look pretty... I just have no idea whether it would theoretically be a good design.

[andrew_mx83]

thats a bit better timbo haha

[TERRA Operative]

What's the go with sizing a plenum for boosted applications. Specifically a 4AGZE?
I'm installing an SC14 with a front mount, so I thought I would ditch the stupid stock manifold and make a nice new one. It's got a 3SGTE throttle body too (upgrade to 55m dia from 50mm).

[Billzilla]

What's the go with sizing a plenum for boosted applications. Specifically a 4AGZE?
I'm installing an SC14 with a front mount, so I thought I would ditch the stupid stock manifold and make a nice new one. It's got a 3SGTE throttle body too (upgrade to 55m dia from 50mm).

Just throw on a 4AGE inlet manifold, it'll work fine - though you'll need to sort out how the bypass valve thingy works if you're keeping it.

[SLO-030]

Ok, here's another. 4AGE 20v, running around 15psi of boost. What size plenum would be required?

I have already purchased a length of 3.5in 304 stainless pipe for the plenum. Will 1.6mm wall thickness be adequete?

CHEERS
Ryan

[JustenGT8]

awww, c'mon! It's the best I could do on my work laptop!

This is the sort of thing I'm thinking. Shouldn't be too hard to fab up, would look pretty... I just have no idea whether it would theoretically be a good design.

Not bad Timbo but if you can keep the air attached around that entry radius that would be better....tough though as needs a pretty shallow angle.

Plenum size isn't critical but a good rule of thumb for plenum volume (including the intake runners to the valve) is around 1.5 to 2 times engine capacity. Go bigger rsther than smaller though if you have the room. That is what i used and only successes thus far

[timbosaurus]

Oh, I see. So the air coming through the throttle body might not be able to 'curve' into the number one runner?

[Billzilla]

Not bad Timbo but if you can keep the air attached around that entry radius that would be better....tough though as needs a pretty shallow angle.

Put the throttle body on at an angle if possible so the angles & curves are reduced.

[JustenGT8]

Oh, I see. So the air coming through the throttle body might not be able to 'curve' into the number one runner?

That's right, plus the detached air goes very turbulent so can result in all sorts of weird inbalances.

Bill's idea is a good one RE angled TB.