ok the way my intake manifold is setup is a dual stage system


I have 3 throttle blades the bottom one (primary) is open at the slightest touch of the throttle while the upper 2 are open when 1/4 throttle or more is applied (secondary).
both the primary and secondary also have different intake runners
there is a total of 4 intake runners. one primary and one secondary for each rotor.

on the secondary side both throttle bodies feed into a plenem that has two runners comming off it. the intake is designed to take advantage or resonance inside the intake to cram even more air into the rotors under load.
looking at the picture I attached you can kinda see the design of the plenum a little
you are looking at the side of the intake where facing the opening of the TB
for simplicity sake I only drew the secondary runners/plenum


I was curious though with how the ports comming from the TB notice how on the inner side of the holes how it is right on the floor of the plenum

but when you get to the outside of that whole closer to the intake runner how the floor drops off quite a bit


was curious if I could more or less create a trumpet shape out of it so rather then having it just having the exit from the TB be at a 90* angle with the wall rather make it a smoother transition kinda like the flare on a trumpet. or could that possibly interfere with the resonance tuning on the intake manifold? also if I where to trumpet the exit from the TB would it be best to do it around the entire hole or just the section where the floor drops out from under it?



how much of a CFM gain would you guess that would gain me? would it make any difference in the pressure drop between the TB and the plenum?
could it slow down intake charge velocity that would hurt the low end powerband. could it affect the tuning on the intake at all? and how much of a hp difference would you guess???


thank you guys

if you need or want any more info please ask and I can give to ya

 

I can't really tell if your motor even has a resonance or not. The sonic pressure wave is created when an intake valve closed completely and the volume of air/fuel in the runners comes to a hault then back out etc. With a rotory motor I can see somewhat of a stop in the air flow but it seems pretty smooth. I'd be interested in the info if somebody has it. With intakes it's not so much the shape as it is the % of cross-sectional area change over length. You don't want to trumpit a runner too much, maybe make a ramport with a small radius but nothing too extream. I can't really understand your picture. Where is the rotor/block in that picture and what direction is it rotating, what view is it, top, side?

 

IMO that design looks like it's based more on fit than on any special harmonics. Given the RPM range of the rotary I also think that CFM capacity would be the primary design concern of the intake.
With that said, it looks to me like the best way to improve the CFM capacity and flow efficiency would be to move the throttlebodies to directly above the runners so the air has a straight shot and does not have to make the 90* turn (actually two 90* turns) at all.
That is if there is room to mount them there.
After that, then normal porting methods to the throttle bodies and runners should increase the CFM. The most common way is to slightly taper the port so that it slowly narrows as it approaches the intake valve.
Sometimes playing with plenum volume just under the throttle body will change the response and power characteristics. A smaller or divided plenum may tend to increase low RPM response, where a larger single plenum may increase higher RPM power.
Shortening the runner length can also increase CFM and sometimes shift the torque peak higher in the RPM range.... though not always.
Out of many opinions out there, these are just mine. They might give you some things to think about.
The only way to really know what will happen is to experiment and test. Throw it on a flowbench. Grab a spare intake to experiment on. It could be that no one has ever done what you're thinking about yet.

 

you do have resonance inside the rotary motor. look at my sig with the clear picture of the rotary. what you would be looking at is the side of the rotor. the rotor kind acts as a valve and unlike the exhuast which the tip of the rotor closes, the intake is closed by the side of the rotor (the side facing you in the picture) and it gives it a good pulse inside the intake. the intake was designed and tune to take advantage ofthese waves. read somewhere that it was supposed to offer almost a reduction of 2in/mg or something like that.

also wasn't talking of trumpeting the intake runner but rather the spot where the air leaving the TB comes into the plenum. Iguess the comparable thing would be taking a 4 bbl carb with a single plane manifold. then at the base of the carb take and make more of a a trumpet shape with each of the throats on the throttle.


sbc305 I gave a really crappy drawing of it, but there are harmonics going in inside the inake manifold, just going for fit they easily could have came up with a better design for the whole thing as well. I can't move the TB since all three units are setup as one whole unit. only way I could move them would be to get 3 indv TB and I wouldn't want to do the work to get that to fit. then the air would still have to take a 90* turn since both secondary throttle bodies feed both of the runners. granted I can add a divider wall in there but that wouldn't work well for my situation, the secondary tracks more or less get used under decent amount of load, or for me racing it. the divider if put there would make it more like a dual plane manifold, hence a lower rpm power band. I want to keep the full powerband on this thing up past 3800rpms to 7000 rpms. and I can't really make the plenum any larger unless I cut this thing open either.


would like to port the whole intake out and taper as you said but would need to cut the manifold for that and I don't have the equip to weld alum back together.. this is supposed to be a low buck op. I have done a little though prolly soon goingto take things back apart again though and port match the runners since mazda had some great ideas with the intake.. but smoked crack on some of the other... they have about 1/4 inch spot where the manifold meets that they do not match up

jprevose I will update the picture for you in just a sec

 

hope this drawig helps a little bit

the first picture I just drew the primary runners kinda to show you how it is setup

on the second picture left them out being not really part of the disction

the red stuff is where it was a 90 angle but I want to blend it in a little more so it is a smoother transition.

 

So what you want to do is smooth the transition into the runners? Without knowing alot of logistics about rotaries, I'd ahve to say from those drawings, that if they tuned any part of it, they concentrated on the lower half of those runners and the relationship between the first and second wave (primary and secondary openings) in order for them to be complimentary. I doubt they did any tuning reaching as far back as the plenum. The wavefronts would likely colide like all get-out up in there.

 

BTW, I'm not Vader, and you got a freebie.

 

hey man any help I can get


and I didn't think it would reach all the way up to the plenum for sure but couldn't remember

I know the plenum will a lot of times dampen the wave from going much further after it reaches that point and also a wave goes from pos to neg pressure (and vise versa) when reaching an opening that is larger or smaller then the pipe it just came in


if you guys want though I can get a desc from the library about the intake and bring it in to you guys to show you a little better detail as to what I was talking about