Intake Plenums, does size matter

[Ben Wilson]

although only 4cyl...

2L
470ps @ 6000
650Nm @ 4500
buggerall plenum... how transferrable this example is??

If you look from the side, there is a hefty plenum there, you just can't see it from above.



Pic borrowed from takai's gallery.

[takai]

I dont think its actually that hefty. Admittedly the valve/port angle does lend to that somewhat, but i doubt it would be near to the "1.5x swept" or the other calculations. I think including the 3" inlet it woudl be about 2.5L max.

[oldcorollas]

on the throttle side of the plenum split.. there is maybe 20mm. on the plenum side of the split (that big flat bit) it is maybe 10mm or less... the big flat area seems to have buggerall volume.
i didn't get a good angle on this photo, but you can vaguely see how big it is... not very
apart from the big long inlet tube, the rest is pretty much just a pancake.

BUT, notice the intermediate plate between the inlet tube and the throttle side of the plenum.. made of a different material (ie shiny, so made from sheet... not cast).... is this a plate similar to the audi rally motor with a small space for air to pass from the tube to the throttle area (ie, split into two halves?) or does it have flow directors to each port or or??

http://gallery2.plebeians.net/d/5065-2/RIMG1831.JPG

[BigWorm]

That is a dead sexy intake setup, but surely individual throttles introduces a whole new kettle of fish.
There's seems to be 3 different setups being compared here, N/A, single throttle F/I and multi throttle F/I. Each setup would have completely different characteristics & couldn't be applid to each other. The focus needs to be kept on only one of these, and I'm guessing Shane you'd be more concerned with single throttle F/I.

Although personally it's the multi throttle F/I I'd like to find out more about.....

[oldcorollas]

hmmm, whats the difference between single and multi throttle FI when you are at full throttle?

edit; partial throttle is totally different i spose... ok, back to single throttle

[takai]

There would be some vague differences between single and multi throttle FI with the actual plate restriction. But thats about the extent of it, and it would make all of buggerall difference.

The big difference is NA to FI plenum setups.

Edit: ergh, how do you keep getting posts in before me

[1JZ.747]

i will always stay single throttle body for my application.

[Ben Wilson]

BUT, notice the intermediate plate between the inlet tube and the throttle side of the plenum.. made of a different material (ie shiny, so made from sheet... not cast).... is this a plate similar to the audi rally motor with a small space for air to pass from the tube to the throttle area (ie, split into two halves?) or does it have flow directors to each port or or??

There also appears to be bugger all room for trumpets - Perhaps the plate is part of some sort of trumpet setup? I get the feeling that this particular plenum is compromised for space inside the car (I assume it's basically mid mounted?).

I do like the idea of flow directors - I keep thinking some sort of cone above each trumpet would be a good thing.

Some more examples of plenum design be found here

[Billzilla]

There also appears to be bugger all room for trumpets - Perhaps the plate is part of some sort of trumpet setup?

Not all trumpets have to be long.
Check out mine on my 3SGE Fraser ->



The ones on my racing car are even shorter.

[takai]

Makes mine look positively long in comparison.

[BigWorm]

hmmm, whats the difference between single and multi throttle FI when you are at full throttle?

There would be some vague differences between single and multi throttle FI with the actual plate restriction. But thats about the extent of it, and it would make all of buggerall difference.

I dunno about that, I agree it comes down to partial & transitional throttle, but surely having 1-1.5 times the volume of the engine (or greater, going by the majority of plenums, factory or otherwise) in between the throttle & the valves compared to 2/5ths of fuck all between multi throttles & the valves results in completely different theories aplying.
The only factory multi throttle F/I setups I can think of are GTRs & GTi-Rs, and the GTi-R seems to have a similar timy plenum to the above pictured 3S, whereas the GTR seems to be somewhere between a tiny plenum & a "normal" sized single throttle plenum, but closer to the average single throttle size, which doesn't really help me understand the theory behind it, but it does seem obvious to me that different theories apply to each setup. I've never seen F/I multi throttle setups with huge massive plenums in front of them comparable to single throttle plenums of the day, or vice versa.

[takai]

The ones which spring to mind for FI with big plenums are the Audi rally cars of the 80s. Ill find pics soon.

[BigWorm]

Pffft, 80's??? Like they knew anything back then!

Maybe we need a different thread for F/I multi throttle plenum designs.... I only recently managed to get my mind off a 20v TB setup with T3 adaptor for mine, but seeing those 3S pics again has get me thinking, again!

[RA23]

The size of a plenum would be more critical if there is more intake restriction, than when there is less restriction.
The more restrictive the intake (air filter, plumbing, or even a given restrictor for certain classes of racing), the more important it is to get a smooth flow in and "level out" the pulses of the engine, which is done by a big plenum.

im paying more attention to those with more thn 15 rep points.

I guess who has given the points is more important than the quantity.

[takai]

Maybe we need a different thread for F/I multi throttle plenum designs.... I only recently managed to get my mind off a 20v TB setup with T3 adaptor for mine, but seeing those 3S pics again has get me thinking, again!

Heh, if the T3/20v takes your fancy then just look at my engine. Ill PM you some details about when im getting it tuned.