intake Idea - Honda Prelude Forum

jsmooney · 09-07-2003, 08:49 PM

I was thinking about making an intake for my friends accord outta PVC - he gave me the idea -

making it out of large pipe first then making the piping smaller gradually (shinking it with couplings twice) as it nears the throttle body.

making the piping smaller from bigger pipe should speed up the air entering the motor, right? if i remember from physics right..... I know this would be ghetto and everyting, but say the piping did not melt and no problems were met with the PVC.

if you could get it right, it would be sorta "forced" induction, to an extent if it worked like i am imagining, right?

Mattsy93vtec · 09-07-2003, 09:05 PM

Kind of... I once tested this theory and found no difference, and that's because of the Venturi priciple (at least partly because). When you start decreasing the size of the tube, the air actually gets hotter (a bad thing) and the velocity of the air decreases while the pressure increases, and once the air enter the intake manifold manifold, the effective area for the air to cover is ~4 times more than the actual diameter of the intake tube. This is why the air must be forced with a turbine because youll never be able to force enough air through the tb just be directing air flow into it.

Factors in designing an intake are basically, how cold the air is when it enters the throttle body, how much air is in the intake at initial acceleration, and the distance of the filter to the throttle body.

edit: confused my own damn self, but yeah, the pressure would drop as soon as the air exits the tb and into the manifold ( http://www.madsci.org/posts/archives...5906.Ph.r.html ) ... sry about that.

concLude · 09-07-2003, 09:15 PM

i dont think so, according to physics:

mass flow rate = A1v1 = a2v2
Bernoulies precipal = H = P (and then some other **** in here)

basically what i'm saying is, as you increase the velocity and decrease the area of the piping the pressure of the air will decrease. Since air is uncompressable at the speeds we are talkn about, you either give up pressure or speed, what your saying will work, you will theroitacally increase the speeds, if the transitions are fluid, the the over all pressure of the air will decrease, yeah its hard to understand but think about the top side of an airplane wing, its a huge low pressure, because the area above the wing and the boundry layer is much smaller then below the wing.

needless to say, i wouldn't waste your time, i doubt you'll feel anygains, on the other hand if you found a way to increase the pressure of the air, i think you'd be on to something, but that why we have boost.

________
..............|_______

............... _______
________|

while the air in the slimmer part of your intake will be faster, the pressure is lower, and like i said thats what creates horse power in naturally aspired engine.

jsmooney · 09-07-2003, 09:15 PM

thanks matt - i didnt think about the intake getting split into four. so therefore, almost no difference would be made because if you gave the air say ~2 psi of boost into the manifold, you would get ~.5 psi per cylinder, right?

does this apply to turbo too? if you boost at 8 psi (cause it divides by 4), will you only get 2 psi per cylinder?

I thought that (from physics again) the air held constant pressure as it spread out? -into the 4 cylinders?

jsmooney · 09-07-2003, 09:18 PM

what if you did an intercooler type induction system (the ricey kind) to get a bunch more air into one spot?

concLude · 09-07-2003, 09:20 PM

my drawing isn't comming out

your best bet is to use the least amount of piping, while getting the coolest air possible, so if you wanna make that thing pop out of the hood i could see that working.

smooth laminar flow would help too, just to cut back on and drag/resistance

Mattsy93vtec · 09-07-2003, 09:23 PM

Quote:

Originally posted by UBetterBelieveIt
what if you did an intercooler type induction system (the ricey kind) to get a bunch more air into one spot?

the only benefit to that system is the cold air.

jsmooney · 09-07-2003, 09:29 PM

i guess the best logical intake is a CAI in this situation, huh? or what about the AEM's that cut off right where the old airbox was?

yield · 09-07-2003, 09:31 PM

Never quite understood the pressure part of this although I know it works like that. I know that the velocity will increase as the area decreases but how does that affect pressure? I like to think of the situation like putting your thumb over a hose. Normally water comes out in a big, slow stream. THen you put your thumb on it and it starts spraying out really fast, but it's also pressurized isn't it??? Haven't you increased it's velocity and pressure - at a certain point you can no longer squeeze down on the water because it is so pressurized. Why doesn't this happen in an intake?

Anyway, I once saw a post by a guy who builds racecars and he basically said what Brandon is saying - you don't want to speed up intake velocity because it reduces the air that the IM "sees"... whatever that means exactly. Guess maybe the Iceman wasn't the best choice after all

Although I'm sure it doesn't make much difference on my little H23.

concLude · 09-07-2003, 10:04 PM

the area your thumb is letting out of that hose is small compared to the full size of the hose. It doesn't make perfect sense, but we an argue until i'm blue in the face, if this wasn't the case, planes would be falling out of the sky.

yield · 09-07-2003, 10:23 PM

Wasn't trying to argue - I was just hoping to get an explanation. The intuitive side of my brain says that things flowing faster have more pressure but I know that physics formulas and such say otherwise. was just hoping someone could explain it to me using a real world example like the hose analogy.

Mattsy93vtec · 09-07-2003, 10:32 PM

... in the end... we're fighting over 1hp probably

true gains will be had in the design of the intake manifold itself, not the intake piping.

jsmooney · 09-08-2003, 12:34 PM

oh well, in my mind it would work, not on the car....

brendon2k · 09-08-2003, 05:34 PM

it would suck because it would not be anywhere near smooth on the inside, causing a lot or turbulence for incomming air.

jsmooney · 09-08-2003, 05:57 PM

you really are whoring up today? you have info in the threads so i guess its no whoring so much.

Yeah, i see what you are saying about the turbulence, the idea is good, but it just wont work

bsi · 09-08-2003, 06:13 PM

id stay away from PVC anyways it gets plenty hot enought to heat that stuff up, and even though it might not melt ill bet $10 that it would be releasing some kind og smoke or gas as it got relly hot