got wide

im building an intake mani for a high boost (30-40psi)gsr with a endyn b16 head. im building it with off the shelf materials from rmr including there D-shaped plenum extrusion.

my question is; has anyone done or think it would be benefitial to weld a divider into the plenum that would essentialy divide the throttle body into two halves, with the bottom of the plenum feeding all runners but mainly the first few or closest to the tb. and the top half would be directed around to feed all the runners from the other side or furthest from the tb?

My thoughts are that this would better equal out the flow to all runners similar to a dual plenum IM but still only have a single plenum. im aware of the other ways to increase airflow to the far runners like tapering the plenum but with this plenum im not sure thats much of an option. im also pretty much stuck with the materials i have as im getting maried in two months and getting the car done in time is in the small part of the budget

so please share any thoughts or theories on this idea or other options with these materials(i know theres good IM builders here) TIA

got wide

heres a 3min MS paint pic to kinda describe what im talkin about

E-Rok

im no expert on this but it looks like that red path is like twice as long. I dont think its needed.

AspectIndustries

Why not just center mount a throttle body to the plenum? *(instead of the right or left)

got wide

i was thinking about that, but dont really think i have the room to do it. i kinda figured this would be the next best option.

i also see how it looks like the red path^^ is longer but i think this would only be a factor when the throttle is first cracked open, and those runners are also still getting air from the bottom path, or i could shorten the splitter plate in the plenum so it ends in the middle so it would drop the air directly on top of the 3rd and 4th runner instead of wrapping around like it is in the pic above. but i dont know anything more than comon sense fluid dynamics and maybe im looking at everything *** backwards, thats why im asking for input from the guys who might have tested this stuff.

k24em2

I'm not sure you'd see any appreciable gains from that

90blackcrx

I don't think your ms paint drawing is accurate, that red line is not gonna curve back into that first runner like that. Either way, its not needed, look into other areas to strengthen the design and performance, I.E , runner taper, air deflection and so on.

harlen

For a boosted app., I highly doubt that plate would help especially at 30-40psi. But for a NA app., I can see it being beneficial. If it's possible you should try it and run a flow meter in each runner, I'm thinking it'll help in the higher rpm range. You may also want to think about plenum volume.

h2.4

I think what you're basing this idea off of, is the "powernow" carb insert? In an forced induction application, I don't think this would be any benefit, and in an n/a setup, I think the intake manifold would have to be redesigned entirely. If I'm not mistaken, the powernow insert was designed to keep velocity up when at part throttle, but this was designed and tested on two stroke, carbed engines.

all_motor_mike

i wouldnt do it. since its a boosted car ur plenum is just a resevoir full of pressurized air waiting for the first set of valves to open so the flow theory that ur pondering i dont think is really nescessary. now on an n/a setup plenum design becomes a bit more important when trying get the power u want where u want. i build alot of intakes but am no engineer, but i gotta say i dont think that would be a good idea even on an n/a engine.


mike

got wide

I understand why the gains under boost would be small if any at all, but does anyone think it would hurt the flow or power at any point.

Also I know on a flat floor IM the flow on the floor area is more turbulant and builders tend to put raise the velocity stacks above the floor. Now the RMR velocity stacks that I have are designed to be flush mounted in the floor. Since the plenum I'm using is D shaped there is minimum flatness to the floor area, so would it still be better to raise the velocity stacks off the floor and radious the outside edges, or better to run them flush to the floor as they were designed? Thanks for all the help so far!

NativeSon

Your illustration is way off base. Your engine uses air one cylinder at a time.
Yes, it will hurt flow and power potential. The only time it'll be beneficial is accelerating from idle. Do yourself a favor and don't overthink a plenum design for a boosted application without a little engineering experience.
It's a pressurized air tank with runners welded to it. That's why people can make crappy looking box manifolds with no math involved, and still see a performance improvement. Just make sure you don't point the TB at any one cylinder, and you'll be fine.
The only time it needs any more complexity than that, is for road or rally racing.

all_motor_mike

whoa there sir, ur not referring to abybody in particular thats posted in this thread now are u, more accurately somebody that makes alot of neon intake manifolds???)


mike

NativeSon

No. And without getting into anything specific, you also have seen some of the work posted here. I'm not here to insult anyone. Just pointing out the obvious. Not everyone is cut out to be a surgeon either.

all_motor_mike

lol, ok just checking.


mike

unusual71

for boosted applications volume and runner design are the two most crucial factors. Also putting a slight taper would probably help and wouldnt be that hard no matter how your making the plenum.

got wide

Have you seen rmr's D-shaped plenum? Not quite sure how I would taper that other than maybe cutting the end of it at an angle to weld the end plate onto but that would also cut my volume down a bit.

Since it seems most think the divider is a bad idea I probably won't do it, but what about the velocity stacks should I mount them flush to the floor of the plenum since the floor doesn't have a lot of flatness to it (less turbulant than a flat floor) or should I raise the off the floor a little?

For reference to the parts I'm talking about
D plenum - http://rossmachineracing.com/dplenum.html
velocity stack - http://rossmachineracing.com/ovalstack.html

vipermagic

For sure don't put that divider in. The very best you can hope for is for nothing to change, and at worst you could seriously decrease your flow and increase pressure drop.

I'm not quite sure what you're asking about with the velocity stacks, though

all_motor_mike

i angle the back half, but for the cars that i made them for i have to in order to clear the rad hose or t-stat housing. there should be no issues with having the stacks on the floor in a boosted aplication, hell im wondering if and how much the gains would be on a natuarally aspirated setup with protruding (full radius) stacks. and not to thread jack or anything but heres 2 made from ross parts (i make my own half round plenum though) with the anlged back halves..........

eco cavi.......








srt4......








mike

got wide

so for a boosted set up, would you recomend not angling the back half if i dont need to for clearance, to keep the plenum volume as high as posible?

all_motor_mike

i dont think there should be any issues with no angle on the back half. but even if there were not something in the way back there i would still angle it just becasue i think it looks a little better than a stright back half. hell mostly all my box manifolds that i make from stock cores have a tapered plenum with a angled back half, on n/a and boosted setups. but on the completely costom ones (which have all been turbo apps.) i do the large half round plenum with angle back half for volume and its easier to make also cause theres less welding.


mike