Really sounds like you should do some research on intake and plenum design.

Generally Speaking:

* Longer intake passages produce more low end torque. The 3.5 runners are no doubt engineered to specifically match the intake pulses. Similar to a Tuned Port GM intake manifold. High end Hp is sacraficed to provide low rpm torque. Good for passenger cars and trucks that are heavy, or need to get a load moving.

* Shorter intake runners produce more high end HP by reducing turbulance, and increasing flow. ie a single plane manifold in a carb application, or individual throttle bodys on an EFI spp..... basically race car stuff that needs super high end HP, and can sacrafice all the low end torque.


Whoever designed that intake system was an engineer, and did not put anything in there they thought would decrease performance, be it HP, Torque, Noise.... I'm not an engineer either, so I usually try to make small changes, and do a crap ton of research to find out how I am changing the whole picture.

I will go look around, and find you some Intake research stuff, and you can go from there.

IF IT WERE ME, I would Rebuild the butterfly shaft with Nylon inserts, or another suitable material, and leave it alone.

IF I could not stand the butterflys any more, and thought I coudl get away with removing them(many folks have) then I would pull them, and the shaft, and tig the shaft holes up, and smooth the welds out on the inside. Hopefully someone here who has done that will chime in with some pictures.

Here are some links for you. Not specifically to intake tuning, but...

http://www.phys.unsw.edu.au/jw/Helmholtz.html


more when I get a chance.

The biggest issue out of all of this is the fact that the part replacement is about 350 bucks. I would love to simply purchase the replacement and utilize the design the engineers intended. (I can't, no loot!) That said, I appreciate your input. I just don't want to slap the old one back on without the butterfly assembly to divert the flow as designed. Maybe the turbulence is the best compromise. The only Monty vehicles to utilize this design are 94-97 SR's so maybe the three year stint is a sign that it was flawed. Again, the proper solution is not a doable solution!(for me)

SO pull the shaft, and tig up the holes.

http://www.rbracing-rsr.com/runnertorquecalc.html

PM me your email and I'll send you a diagram of the plenum. you'll be able to see all the weird bends and holes.
I am perfectly aware that I can plug the holes and move on. It's just that I found some used intakes from newer montero's and 3000GT's for around $40 and figured "hey I can just grab one of those, throw it on and have no turbulence...alright!! sweet!!" ... It sounds like the GT won't work, but what about a '98 3.5 or even 3.8??

I PMed you back, dude

Brendan

Thanks Man, got it!

I see your picture.

How would there be more air turbulance after you removed the butterflys as opposed to when it is functioning normally, and the butterflys were open?

When it is closed, the intake passages are longer, and provide the low end torque, and when it is open, it's tuned for more power at a higher RPM. Very cool I think. Apparently you need to build the bushings for those butterflys out of a quality material or they will kill your motor upon ingestion.

The long butterfly runner ideas were first designed by Porsche engineers and found to actually provide a positive intake pressure that increased cylinder filling. Fiat also used them.

Turbulence is sometimes a good thing - particularly in an intake tract at the point where fuel injection and subsequent utility are concerned:



If you want to pay the price for a download, the entire technical paper can be obtained here:

SAE International

Frank

You have to think in waves of energy, and flow in cfm. The way I see it, you at worst have two converging flows without the butterflies. Each of these will be at a lower velocity than the originals, but total volume may actually go up. You could also get some extra turbulence from the converging flows.

Now look at the helmholtz waves. The runners are different lengths to tune the helmholtz effect at two different rpm ranges. Long runners for low rpms, short ones for high rpms. The reason for this is that the helmholtz waves propogate thru the air in the runners at a constant speed. In the intake, when the valve opens, it creates a region of negative relative pressure that propogates thru the air medium at the speed of sound. When the vac wave hits the end of the runner tube(s), it reflects back down the tube, but as a pressure wave instead of a vac wave. If the runner length is tuned so that the returning pressure wave hits when the valve is still open, it shoves some more air into the cylinder than just the runner flow would allow. This pressure can approach 10psi. Now you have two sets of waves. One set hits at the right time. The other set hits wrong, at least at that rpm. The waves may also be slightly weaker from being split into two runners. Dunno.

All that said, I don't think that any power loss is worth even hacking a $40 JY manifold to try to get it back.

Just turbo the damn thing and quit having to worry about Helmholtz effects to fill the cylinders...