Couple of questions, first
If you were to make an intake runner for 2200rpm and tune it for 60 sonic bounces, would that same runner be tuned for 4400rpm with 30 bounces and 8800rpm with 15 bounces? I want to know so I don't need to design a variable length intake just have a few rpm points where it gives good power; down low, mid-range, and up high(if I get that high).

And while playing Ridge Racer 5(I know its a game but stick with me) I noticed one of the upgraded turbo engines went from the normal log style turbo headers to a short tube equal length header. Are there any gains to be had by having really short equal length exhaust tubes all collecting right at the turbine?
TIA
Brent

hmmmm I didnt understand any of the stuff you just said

If you posted the type of model you are using or your equations, I could probably comment. Also, are you talking about intake manifold runners or another intake pipe?

Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

I really need to pick up a book on this stuff, I got this equation from somewhere online that a 2gnt member found and its seems basic to me but should get the basic job done. I programmed my TI-83 to do it for me so let me see if I can decipher it correctly theres a few steps the way I have it: 60/(rpm tune point, ie5200rpm)=A(forgot what it is, but should be seconds per revolution)
((720-valve duration)/720)x2=R(number of revolutions valve is closed)
AxR=S(seconds valve is closed) Speed of Sound(~1300ft per sec according to the site)xS= Length of Intake runners for one reflection. Its based off the fact that when the valve closes it causes a pressure wave that moves the SoS backwards up the runner which bounces back when it reachs the upper manifold and you want the valve to open when it comes back. The answer you get will be an intake length in feet, so according to the site you have to divide it by how many bounecs will take place in the runner before the valve opens so you can shorten the runner lengths. I just noticed that I may need to divide the final number by 2 since I dont think anything in that equation accounts for the reflection back down the runner, so I may be making things twice as long as they need to be. This has been a lot and I hope you can help!! TIA
Brent

so, you want to know if the sonic percussions is linear with revolutions? i dont see any reason in the world why it wouldnt be, but consider this: the velocity of sound isnt constant. the medium is obviously air, but it isnt "atmosphere at sea level" air. the intake charge is 1) heated 2) of a displaced pressure, whether it be positive for turbo or neg for NA. 3) most likely very turbulent. thus, i dont really think that there is a completely algebraic way to go about solving for the optimum intake runner length or the optimization in the variability of their length. plus, all sorts of other factors are in there, like the precision of calculations, true air flow, and most importantly, the precision of the materials and tools used. unless you doing a comlete reseach test with stereolithographic models, vaccum cambers, 3D CAD programs and extremely precise laser guided-computer controlled equipment, i would actually try to go for a trial based testing route. and i venture to say this, this is most likely speculative. are you doing this for a school project or just want to tune to the extreme? and just for s&g, use metrics, it'll be easier. cya.

I was thinking about the air temp thing and was gonna look it up, but I hadnt thought of intake pressures and such. So that could change the lengths enough to warrant a looksy online! I don't really need it to be exact to the rpm, but atleast it should give a general idea where to start. I'm doing this because when I'm not doing anything I think and when I think trouble happens :) , so I've come up with a bunch of performance shit I want to get down and work with. I wanted to make a variable intake but theres a lot of fabricating, and electronics work that I can't see me getting done sicne I'm no engineering major and don't know any, so i thought an intake tuned for a few points would be easier. The only other problem is runner diameter and flow at the diff. rpms but I think I've got that figured out. Later
Brent

Actually I disgaree. The integrated velocity of melonchrite is substantial if not patronic while the differeing equations develope more tranigent forceteds of differing degress of technical frinopolies. But I might be wrong.

these malapropisms are purely quixotic. :rolleyes

I'm with IrishEclipse...from what I've seen, you can't get a very good design without test data, modeling software, and a machine shop. The best those equations can get you is "in the ballpark". I had to design a couple intake manifolds in my IC engines class, but the mathmatical models I had to use left out alot of factors. There was just no way of really accounting for some of the stuff. I think your best bet is to make some calcs and test a few prototypes. You may choose to incorporate sleeve joints and silicon couplers on the runners to allow you to change runner length quickly. I believe I've seen 4G63 manifolds like that.

Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

Parts Collected for next engine:
2.4l PT Turbo pistons
2.4l PT Turbo rods
2 Rolls duct tape

Yeah I was thinking I would make a self adjustable one so I could get the fine tuneing down and such. If I can make the adjustable one easy I may just make the electronics and servos needed for it, I dont know. Any ideas on the second question?

from what ive picked up, equal length runners help by getting the exhaust pulses in time, meaning that the stream to the turbine is more constant, and from what i imagine, more efficient? also, the tubular design is just obvious i think: gasses travel and flow better through a round space than whatever is in the log type. why do you think porting and polishing the Ex-mani is beneficial? freer flow, no doubt. if i were to try to take on this project, i would work off precedence. use the resources already available to your disposal as often as possible. hope this helps. P-sout.

keep in mind that the speed of sound (mach 1) is not 1300 mph but between 741-750 mph depending on altitude. 420aTurbo

What you need to do is try to get a look at some variable length intakes, one of the new Lexus uses a butterfly valve that runs off of RPM that shortens the intake for horsepower as you rev. If you are looking for exact measurements, your going to need a lab and a lot of other stuff but with so many variables its impossible to make an exactly perfect intake for every situation. I was thinking if you could run a program off of your ignition or a tach that would translate that rpm and correspondingly change runner length that would work, but on our cars I think that wouldn't be worth the effort for what results you get. I have a sort of idea for an extreme intake that would be high power at 3 different points like you said but I'll have to look into it more, you're going to want to know a lot of things about your motor for any of this to work. As far as exhaust manifold design goes, I wonder about the efficiencies of equal length or just log style. If your exhaust pulses hit at the same time, your turbine is going to get hit by a good amount of exhaust to turn but it has to wait for another pulse to hit before getting another blast to turn. On the other hand if they hit in succession, you have a continual blast of exhaust to turn the turbine and it becomes stronger obviously as rpm develops. That sounds like it would work better against lag. Give me a couple years, I'm only a freshman mech eng.

haha, I'm a freshman in nothing right now. I have my high school diploma and one year of college down(but didnt return so yea..) So most of my knowlege comes from people who know anything, websites, magazines, and 2gnt ;) like I said I need to buy some books on this! As far as the Speed of Sound, I was doing Feet per Second which I actually found that at sea level its ~1100fps and at 100,000 ft altitude its like 800fps, so I figure with the engine vacuum its around 600-700fps and changed my calculator program for that. Also when the intake is tuned for a certain rpm how do you know, is there a spike like 1000rpm or so in size? I noticed on a dyno for an eclipse there was a spike ~3800rpm that seemed out of place!

For you engineers out there, what were the classes like and what did you major in, I'm open to different degree ideas right now and stuff like this has always interested me. But math has been a pain in the ass to learn, I like math I just suck at normal math classes if that makes since.

there's no way in hell you fuckers are speaking english

im in aeronautical/aerospace engineering, so this is right up my alley. im really interested in following the development of this project, so keep it up. as far as the spike, ive got no educated idea. my only guess is somethingto do with the frequency of poeration, as every frequency in a closed space has i forgot what its called, something half-wave propagation. anyhow, its the peak reasult in constuctive interference. that;s all i remember is that a wave doubles at a certain frequency in a constant realm of operation (density, volume, etc etc). and, uhhh... conventional speed(s) of sound at different altitudes is most definitely not applicable to this situation. it is based on factors like temperature, humidity, and barometric pressure; so look in a physics book for usable figures, not a weather book. im guessing you want to set some of your mobile factors to constants, unless you want to do a LOT of differential calculus. use the veocity of sound in air at a set location on the pressure map so that you'll get the best results in a certain rpm range. you dont want to try to change to many things at once as to get a constant increase in . id say go with a point with a minimum in power, to get the general gains up to a more level slope. ok, enough for tonight. cya.

If you want to read alot about forced induction and the associated systems...try to find "Turbocharging and Supercharging" by Allan Allard at the university library. It was written in the 80's, but still has lots of good info. You should also be able to snatch up a recent "Internal Combustion Engines" book at the university bookstore. Most universities with engineering majors will offer a class in IC Engines (so you can buy their book). I forgot the author of my IC Engines book. That book should have stuff about designing intakes and exhausts.

As for picking a degree, definitely check out engineering. If you love designing stuff and taking things apart, then it might be for you. You should be decent at math. Math is the backbone of mechanical engineering, at least. You should also be prepared to spend alot of days, nights, and weekends in front of a book/caculator/computer. I can tell you, I didn't have 1/3 the free time that my polysci friends had. I can also tell you that it was all worth it for me. I wouldn't be happy as anything except a mechanical engineer.


Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

Parts Collected for next engine:
2.4l PT Turbo pistons
2.4l PT Turbo rods
2 Rolls duct tape

Corbin,

Dude I probably need to talk to you a bit about engineering then because you are what I plan on being as of now. But I'm getting romped in Physics 131 even though I have the highest grade in our class in Calc 1. I know the basis of mech eng. is physics so you think you could drop me an e-mail?

lhousing@tulane.edu

Thanks a lot.