After watching a video about an S2000 with ITBs, I'm convinced I want this for my 13b Cosmo...when I get it.



Anyways, I just wanted some information about this and rotaries.



Maybe someone can enlighten me?



Right click, save as.

explain to me why? https://www.nopistons.com/forums/pub...1047683561.gif

There are quite a few places that offer IDA and or DCOE manifolds for 13B's. The only off the shelf manifolds that I have seen for the 13B-RE have been IDA style, which use IDA style throttle boddies that can be purchased from quite a few places. http://www.twminduction.com is one place to find the TB's, you can try ebay for the manifolds.

I'm with you

Better breathing.

http://www.tweakit.net/shop/images/Rotary1C_sm.gif



http://www.tweakit.net/shop/images/r...12-3146_sm.gif



http://www.tweakit.net

Here's where that guy got his.



Lance Hayward

Generally speaking more useful on laaaarge ported N/A motors, but have been used sucessfully on really high power turbo engine aswell..

Only when the std. inlet manifold becomes a restriction.



Having said that this will be one of the next mods to my car.. mainly because i'd like to play around with different runner lengths since my engine is now got a reasonable sized street port https://www.nopistons.com/forums/pub...IR#>/smile.png





I've also seen, over here in Oz, people use individual throttle bodies, Ie one per inlet runner, 4 throttle bodies in total all feeding a different port runner. A very good idea. imho, since you can have longer/shorter runners depending on which runner has more timming. I think all the top running cars in improved production here use this style setup(on ~300hp bridgeport engines that don't cut into the rotor housing at all!!)

Would the use of 1 TB for each intake port increase torque?

Yes, if you had the right runner lengths and cross sections chosen.... https://www.nopistons.com/forums/pub...IR#>/smile.png



It's all a trade off really when it comes to inlet runner choosing though, you will add torque somewhere, just depends where in the rev range you want the torque to be added to really.



...you can't get your money for nothing and your chicks for free..... https://www.nopistons.com/forums/pub...#>/biggrin.png

I only have one question for now. What the hell do you do with the stock primary injector ports or are they still used along with the 4 injectors on the new setup?

if you want better driveability use the stock primary spots. mazdas got some graphs, they used the stock primary location on the 787, where fuel efficency was important. the higher location gives 1-2% more power, but it takes more fuel and driveability is worse

*sigh* No, wrong answer.



A well designed plenum-style intake manifold is actually capable of outflowing any ITB setup. Period. Through harmonic tuning, you can get a lot more energy to help force air into the ports than with an ITB and you can do it over a much broader set of RPMs. The plenum and whatnot helps recover a lot of the little shockwaves bouncing around, and there's no real reason it would have any more flow restrictions than ITBs aside from lousy design.



The reason ITBs are used on race cars is pretty simple; throttle response. There's very little volume between the throttle body and port, so that when a change in throttle position is made, the engine responds almost instantly because there's less air mass and thus less inertia. Oh, and they're also easier to fabricate and package. Of course, these advantages sort of disappear with forced induction cars; with a turbo, you have to wait for the air mass in front of the throttle plate to catch up, so the air mass between the throttle and port isn't much of a concern. Another downside is that throttle control is a bit more edgy; below something like half throttle the ITBs will flow quite a bit less than a single butterfly for a given throttle position but they suddenly start catching up closer to WOT. To put it another way, a lot less control over part-throttle, which is where most people spend their time driving.



That said, ITBs *are* easier to fabricate and sometimes off-the-shelf intake manifolds are just completely unsuited for an application. It's dead simple to make velocity stacks coming out the side of an engine, but a well designed plenum manifold takes a bit more thought... sometimes more than the manufacturers can manage. https://www.nopistons.com/forums/pub...#>/biggrin.png

Wow, thanks for the information. https://www.nopistons.com/forums/pub...IR#>/bigok.gif



That was just my guess, obviously, because I don't know anything about this kind of stuff.



So who makes intake plenums for 13bs?

Heh, sure... gotta learn sometime, or something like that. I get bored between classes and write stuff, so... pardon the verbosity. https://www.nopistons.com/forums/pub...#>/biggrin.png



As for who *makes* plenum style manifolds... well, that's an interesting question. I don't know that anyone really does off the shelf. I mean, you can get them built, but...



Everything I've heard though says that the Cosmo 13B has about the best intake manifold Mazda stuck on a factory car (except maybe the RX-8 one) so personally I'd just be looking at options for a bigger throttle body on it.

What about using these ITB "kits" on na's?

Not sure where you are coming from on the apples to apples comparison here. If you take 2 setups, both with optimally tapered runners terminating in a volume with decent bellmouths to get a good reflection, but one has butterflies in each runner and one has a single butterfly in exit of said volume, then as far as the air is concerned you have identical systems and both will flow the same.



If you are saying that plenum is short runners and the main resonance being due to the airbox/inlet tuned system vs a long runner IR setup, then the IR setup will flow way more, simply because the reflection pulses off a closed exhaust valve have a far higher intertial supercharging ability than a helmholtz resonance due to a plenum. However the length of that runner is critical and in most cases is way too short to get the main reflection coming in at a useful time.

damn that guy has a lot of money for his age

Excellent.



Thanks for the info. Although I don't have the motor yet, I'm already thinking about stuff to do to it. https://www.nopistons.com/forums/pub...IR#>/bigok.gif

Well, on NA motors they make some sense... and you could make the argument that they will flow more because the stock manifolds are crappy. I won't say whether that's true or not because it depends on powerband the engine's tuned for, and I don't really have numbers anyway. I personally am building an IR manifold for the motor that's in progress, probably fed by a Weber IDA. It's going on a peripheral ported engine though, so... https://www.nopistons.com/forums/pub...#>/biggrin.png





Well, the specific apples to apples thing I was looking at were some Honda tuners. Another one to look at is what kind of manifolds various drag racing classes are building; sheetmetal "tunnel ram" manifolds being the norm. I know there's others out there but I can't point at them quickly; I apologize for this being briefer than I'd like, but I have studying I have to do.



Taking two setups like you said, you're right they are about equivalent. There's small differences because of how much port area is being taken up by throttle shafts and butterflies, but we'll ignore that. https://www.nopistons.com/forums/pub...DIR#>/wink.png



You were pretty much hitting it comparing a short runner plenum setup to a long-runner IR setup. If you can *make* an IR setup with long enough runners it will flow the same (at reasonable RPMs) The trick is, to do that the runners start getting impracticially long. You're getting the 2nd and 3rd order harmonics to help out, but 1st order harmonics aren't doing anything unless you're running Formula 1 RPMs... quick and dirty calculations suggest a pipe length of around 800mm to get 1st order harmonics to be useful at 8k RPM. With the plenum you can tune it to get those lower order harmonics and still package it.



This is off the top of my head; specifics might be off. An interesting note though is something I saw at the SAE World Congress; Opel had one of their V8 touring car race motors there. It was using 1 throttle body per cylinder *AND* a plenum for each bank of 4. Best of both worlds?

The Skyline GT-R engine is the same way. A big plenum feeding the ITBs. I believe the Pulsar GTi-R uses this system as well.



J

If you try and get a plenum to resonate at above 3000RPM then it becomes impractically small to get a good shot at the runners. Witness the fuel distribution problems many v8 manifolds have. Drag racing is often odd, because of the rules that you have to run. Dunno if that is why tunnel rams are popular as I've not yet seen evidence that they are good at high RPM.



Have a look at www.bgsoflex.com/auto.html and click on the intake resonance calculator. I've compared the results of this to dyno runs and the correlation is very good. This is on a 1.6litre 4 pot pumping out 208BHP at 8000RPM (that's flywheel BHP calculated from coast down tests on calibrated rollers, so about 220 dynojet wheel HP). Its a street car during the week.



Being pedantic, if you have a tuned volume before the butterflies, its an airbox, after the butterflies its a plenum.



I've looked at the theories and they all show that the resonances due to runner length are far stronger than those due to a helmholtz resonance in the airbox/plenum. Now I come from a county where IR is the norm for a performance application so am biased. I also think real cars should have the intake trumpets poking out the bonnet. An air box then can be used to fill in the low end and you have your cake and eat it



Bill

the 787b also has a big airbox over the runners

I second that.

Isnt it bad to run the ITBS with no filter of some sort like on that s2000 in that one video?

i was thinking the exact same thing.

I have to wonder how much good pulse tuning a rotary intake is going to do. Evidently it does work to some extent otherwise the 787B wouldn't have used the variable length runners. But since a rotary draws air all the time, as opposed to a boinger which only draws air about a third of the time at most, it will not get anywhere near as strong pulses in the intake as a boinger will.

Not quite, you still get a pressure event from inlet open and inlet close. However compared to a piston engine you are tuning to different reflections. In piston circles you tune off the inlet closing, which then gives 450 or more degrees for the pulse to fly up and down the runner one or more times. The rotary does not allow this so you only have the 330 or so degrees that the inlet is open and cannot have multiple reflections (you can but they don't seem to help much).



So the resonances that you have to tune with are:



Relection caused by inlet opening (negative pulse heads up inlet, reflects at bellmouth to postive pulse and heads back) in same cycle

Above coming back in NEXT cycle

Helmholtz resonance due to runner/rotor combination

Exhaust scavenging pulse.



Some of these will help you, some will hinder, depending upon the set of compromises you are tuning fo

In a rotary, the pulses are stronger. There is no valve to get in the way, and theres a more direct path from the chamber to the runner. Rotaries respond VERY well to intake and exhaust manifold tuning.

it is bad, he should have something on there

So then what's with the lack of aftermarket intake manifolds?

No shortage at all. Look at www.japperformance.com.au to name but one.

While the hp gains are there, paying customers arent. Not here at least. Turbo envy runs rampant here.

The stock manifolds use both the opening and closing pulse, but because they are both positive pulses and much stronger then a piston motor, we use them in a differnt way with opposed secondary and primary runners so the positive pulse isnt reflected, but just carried to the other rotor during its closing cycle. the opening pulse is positive and not negative like on a piston motor because of the rotarys overlap with the exhaust, which when the exhaust first opens trys to revert the intake charge and creates a positive wave. Stock type manifolds would work much beter than individual throttle bodies. S4, S5 NA, and im pretty sure the s5/s4 turbo use this system. Also the S6 and rx8 use this system of intake manifold tunning, its VERY effective on a rotary.





Documentation: http://www.thecarricos.com/ACRE/Docu...tech90-1-6.pdf

Not quite. There is a reversion pulse that can be used outside the tuned frequency of the exhaust, but at higher frequency there are at least 2 negative pulses. One is from the scavenge pulse from exhaust tuning. The other is from the expanding volume in the rotor chamber.



The mode you are referring to is generally used at lower RPM.

A classic example of having just enough knowledge to think you know what youre talking about, but not enough to see the big picture.



The pulse from opening of the chamber is ALWAYS negative, regardless of whether its a piston engine or a rotary. The chamber is expanding as the port is open, hence the negative wave. The air horns on an IR setup invert that pulse back into a positive pulse that arrives back at the port just before closing. The closing of the port traps the high pressure pulse, which results in an increased VE.

So the performance gained by independent throttle bodies is of no use on a turbo motor?

You are a classic example of someone who thinks they know to much, and thus are not open to new (to you) ideas. The SAE paper from Mazda says, and i quote



"A high powerd rotary engine was realized by developing a dynamic supercharging inductions system which uses interference of two kinds of compression wave:



(1) As the intake port begins to be closed, the air pressure risses due to its own inertia as shown in the top of Fig. 9. The high pressure creates pressure wave which moves back up the intake at the speed of sound and down the other intake pipe to feed more air into the other port.



(this is the important part, read carefully)



(2) As shown in the bottom of Fig. 9 the residual exhaust gas, which still has high pressure, is blown up through one of the intake ports and puishes against the intake air momentarily, thus raising the pressure. As a result, a (****) high pressure wave (****) is sent down the other intake pipe cramming more air into the other intake port."



Also if you look down the page, there are nice little figures and graphs showing the same thing. Figure 10, in particular, the two pressure spikes from the the two events described can be seen twards the left of the figure, the first spike is the intake closing even, and the second spike is the intake open event.



I am well aware of how a standard plenum/ air horn system works.



Let me ask you this, where is the pleunum/ expansion chamber/ volume change in ANY of mazdas stock intakes? The rx8 doesnt have one, the 86-88 NA's dont have them, the VDI equiped 89+ NA's dont have one (you can EASILY see this the damn high rpm path is a nice constant volume loop from one secondary port to the other) and the FD doesnt have one. You need a large change in volume to reflect a wave, so where is it on any of the tunned manifolds i mentioned?



This form of wave tunning mazda has found very effective, however it is not the only way to do pressure wave tunning on a rotary. The R26b uses air horns on its variable intake, which work exactly like they would on a piston motor, reflecting the wave back with a revesed sign. I believe the 13b RE and the 20b also use normal plenum tunned systems.



Please, atleast read my documentation before ostracizing me, im am not making things up, only repeating what i have read from reliable sources.

http://www.thecarricos.com/ACRE/Documents/...-tech84-1-6.pdf



Qoute is from this SAE paper

Also plenum style intake tunning will work fine on a turbo, a turbo motor is just like any other motor, except its sucking in air that is 2-3x more dense (1 bar and 2 bar respectivly) intake tunning still applies as shown by mazda's choice of opposed intake runners (non plenum style) for the fd3s, and there choice of a plenum style for the 13bt



http://my.engr.ucdavis.edu/~pko/13BTvs13BREW.html



This site also backs up my previous thread by stating that the fd3s uses dynamic effect intake, and has opposed runners with no "surge plenum tank".