Whizbang

Well, for several reasons, i need to make a custom UIM and LIM. There isnt just not enough space to fit the FC turbo LIM with the turbo mounted as it is. The plan was to use the FD lim but that isnt going to exactly mount to the engine. So...

i am starting to plan a custom intake manifold. Im figuring on using a plenum about 15cmx10cmx20cm which should give me 3000cc volume. which is a little more than the motor displaces. Additionally, i am going to have partition to divide the two runners to seperate the pulses. like the factory manifold. going to utilize the stock TB.

i have material details in mind for runners, injector bungs, etc.

but does anyone else have some input or pictures of custom manifolds on the rotaries?

RacerXtreme7

iTrader: (2)

http://rotaryaviation.com/intake_manifold1.htm

Whizbang

well im not going to fork out 200 bucks for cast stuff. i have the ability to produce the flanges and cut and weld runners. plus its going to made out of steel, low-carbon, seeing im a college student and have no money.

ikari899

search is your friend please use it

https://www.rx7club.com/showthread.p...=intake+design

but i got it for you this time

j200pruf

iTrader: (4)

Does anyone know what motors that rotary aviation cast LIM is made for?

Whizbang

holy crap that link had alot of information. well time to start designing.

ikari899

yes you are. it takes awhile and the problem is in my opinion is that they do not go into alot of facts about WHY stuff is the way it is

Whizbang

what exactly was that in reference too?

ikari899

that thread, it just doesnt go into some things i think it should cover. but yeah its alot of stuff. so take your time and understand it. are you a ME in college?

rotarygod

iTrader: (1)

By all means go into it then. I am never going to go add to it and I easily could. I took a lot of time to write that out only to have many people argue about it which is pretty typical with many on this forum (not aimed at you. Just a generalization). As a result I am never going to contribute in length like that to this forum ever again. Small simple answers from now on.

Asleep

Been there on other subject matter.

But I did read the thread and copied some of the formulass into my SAVE folder. Even though no one else might have, thank you for that sharing and the time and effort that went into it. I missed it when it first came out but discovered it when it was linking into this thread.

Whizbang

yeah i printed that out for reference.

ikari899

dont get me wrong that thread is absolutely amazing and should be kept forever because you really wont be able to find that much, great, information on rotaries, any where.and its not that i know it i just would have liked to know more about the fluid dynamics part of it and what not. because i do know a little makes so many more questions pop up . im not trying to play down that thread cause its amazing. if that link to the ppt still worked that mighta helped me out alot but it didnt.. o well im just going to have to wait till fluids... poop...

ikari899

and honestly i have to many questions when that sorta stuff comes up i would need to sit down and talk to you about it for hours and write stuff down while i thought of more questions. i wouldnt be able to ask enough questions on the forum .

i for one worship rotarygod , and other engineers who get into this stuff

Whizbang

so i had a thought while i was drafting out the design. The pressure wave exists because of the opening and closing of the intake ports, correct? so because im going to design it for future use, and i plan on running a full brigde on the motor, what happens when this type of port is used? I know there is overlap so wont that effectively eliminate the pressure wave?

ikari899

valve timing chnages

Whizbang

no, what i mean is the pressure wave is caused by the opening and closing of the intake, but the bridgeport elimates alot of that. so is the pressure wave also eliminated?

ikari899

welll I don’t know much about bridge ports so i cant talk about them specifically, but I do know that bridge ports just have different opening and closing times. P port motors are the only ones whose intake tracks are ALWAYS being utilized and even then there are waves created. So ill talk about those.

When the first chamber sweeps by air is being drawn into it. Then as the port is closing and the next chamber is opening up there will be slightly higher pressure due to the overlap, exhaust intake, turbo, etc, etc. this is also the reason they must idle so high because of this huge amount of over lap. Any who the higher pressure well creates a high pressure wave and it does its thing the chamber moves on the next one opens and so forth. Not as many waves are made because the intake port runners are ALWAYS being utilized there is never a time when any air is “not moving” this also aids in the higher rpms because the air builds up so much inertia it just about starts forcing itself in there in sorta the same way a siphon works.

I am assuming the bridge ports acts almost like this but in my thinking there has to be time where the port is closed with side ports… I dunno, like I said I haven’t looked into them at all.

At least that is my belief if I am wrong some one PLEASE tell me so I know I’m not giving out bad info.

ikari899

incase you are starting to get confused there are 2 causes of pressure waves. the port opening on a normal motors and a low pressure wave being created. the port closing and a high pressure wave being created. you must take both into account when making a intake manifold unless its weird like the Pport where the over lap creates a highpressure wave when the port opens

ikari899

and as long as im at it i have a couple questions have come up while concerning the design of a intake manifold for pports. because there is no closed time you must tune using the high pressure wave created when the port opens but when the wave comes back it is going to have to travel the length of the chamber to fulley revert so are you going to have to factor in that differential length?

rotarygod

iTrader: (1)

ikari: don't take anything I said wrong. I wasn't getting on your case for anything. I do realize that there are many things that I could have added. I have a way of typing out really long threads and it's hard to remember everything at first. Once people start commenting it becomes even harder to add to it while still trying to answer other questions. There are a few things I've learned since I typed that so it could use a little bit of ammending. It primarily is accurate from the standpoint of a plenum type of intake system. There needs to be more detail about individual runner systems as well as intake effects on peripheral port engines. Some of what I said is easy to confuse as I lumped a few different tuning methods into one post. The Helmholtz effects could be separated out better. An example is where I stated that the plenum should get smaller to tune for higher rpms. I didn't state what tuning method that was. With Helmholtz tuning methods this would be true but typically the opposite is true without. It can get very confusing very fast but then again intake design isn't a simple thing.

Due to the many differing responses that you'll get on the forum, some from people who actually know what is going on and others from people have have no clue but think they do (larger number of them!), it gets really hard to convey anything with any degree of accuracy anymore without someone telling you that through the grapevine through someone else's common sense they heard it was wrong. For this reason, it isn't worth it to me to add to it. I definitely think the info is good and would benefit from being completed. I'm just not going to take the time to do it.

ikari899

llol tell me about it, some people just wont listen at all because they some how KNOW EVERY THING ALLREADY!!!

and i agree with every thing else you just said.

any who i have tossed together some spread sheets of formulas i created. i figured it would be best if i just ignored just about every thing any one has said and created my own.

well the numbers are all below the numbers that the standard equations put out, and thanks to you and a fluid mechanics book i figured out why you subtract 1/2D.

for those who dont know its because the wave is not a plane traveling down the runner, it can be approximated with a sphere although as the runner shrinks the wave front becomes more elongated. and as it gets larger it becomes more and more like a plane . but it can all be aproximated by calling the wave front surface a sphere. at least thats my understanding.

BUT the one i made for P port seems to line up the the rumored 16+ in at full extension for the 26b with my stuff giving 16.7" for 6000 rpm assuming a 1.5" dia runner so that could move up and down a lil' bit.

like i said to many questions, not enough forum!!!

o well i will keep plugging away at my equations and spread sheets in order to find and correctly learn why the standard ones are the way they are or if they are all wrong!!!

rotarygod

iTrader: (1)

Actually it doesn't work for the P-port manifolds. Remember that when the 4 rotor's intake manifold was fully extended, it wasn't 16" long. It was 16" longer than at it's shortest point. Since the moving part of the manifold had to fit inside the remaining intake, that would mean that at the shortest point it is at least 16" long but actually a couple of inches longer. Fully extended it is over 32" long and probably closer to 35" or so. You could always change the reflection value to see if that helps but from what I remember it doesn't. As I said, it's really a formula for plenum based intake systems and not individual runners. I need to sit done one day and work all of that out.

RXBeetle

I'm glad this topic is comming up again.
ikari899 sorry to not answer you back in my last thread on this topic, it sounds like you are going much further in depth with your calculations with wave shape and all. The spreadsheet I was working on was just to equate runner length with port timing-rpm-#of reflections (I threw tempetrure in there too just to see how it changed things). Simple distance speed time stuff. I it's almost pure jibberish to anyone but me right now (not much labled and some stupid auto-formatting tht makes it not want to recalculate cleanly when I change values) I'll have some time to play with it some more and clean it up soon (midterms/onslaught of urgent jobs at work right now )

I ran across some info that may help... (linked because the pics are huge)
http://www.rotaryeng.net/Mazda-p-por...e-enhanced.jpg

Dyno: 24.5 in. runners
http://www.rotaryeng.net/Weber58-24....yno-curve2.jpg

Dyno: 28 in. runners
http://www.rotaryeng.net/Weber58-28i...dyno-curve.jpg

PS I don't think this post should go without giving credit where credit is due. Thanks to the people that go to alot of work to share the indepth technical info that is basicly free research for the rest of us.
Thanks to rotaryeng.net for the above linked graphs and rotarygod for spillin his brain on the web it is much appreciated.
Pay a few grand for a college engineering class just to get some arrogant prof that can't speak english and has never been out of the acedemic world and you will know the true value of knowledge and experience as opposed to educated idiots.

rotarygod

iTrader: (1)

When I was in school going after an ME degree, I had the same problem with math teachers. I couldn't understand any of them. Who says math is the universal language!