6G Celicas Forums

lol i just caught that

You dont loose pressure if you lengthen and decrease diameter. If I have something that is 14in long and 3in diameter that gives me 99 cubic inches , and if I extend it to 18in with a diameter of 1 3/4in it gives me 99 cubic inches of volume. So if I have the same volume I have the same amount of pressure.
The equation for Volume is;
Pi x radius squared x hight
or Pi*r2*h
or 3.14*r2*h
The equation for pressure is;
normal force(14.7)/area=pressure
or F/A=P
or for cars 14.7/A=P
The only thing you change when you change length is distance ie the time it takes to reach the car.(I dont think you really want me to get into the math of that to)

This post has been edited by hatchy_gt-s: Jun 17, 2010 - 11:59 PM

good stuff...surface to volume ratios...you want more power...swap to turbo and keep it at the 3" mark

So again, how does changing the length of the pipe change flow rate or pressure? As you just said, the only thing that changes with length is the time it takes for air entering the filter to reach the throttle body (essentially). Changing the volume of the pipe won't change anything as long as the volume change is due to length and not diameter. As air is used by the engine, the air at the intake end of the pipe will displace the air that was just used due to the fact that a gas will expand to fill its container. Thus, as long as there is always air in the intake pipe (which there is, there's no vacuum there), there will always be the same pressure for any given length of pipe of the same diameter. Volume is entirely unrelated to pressure in this case.

In a closed container, volume and pressure are inversely related, absolutely. However, an intake pipe is not a closed container, one end is open to the atmosphere, the other feeds into the throttle body of the engine. Since this is in the case of a N/A engine, the pressure inside the pipe will always be 1kPa (roughly) no matter what the pipe's volume. The flow rate is entirely related to the diameter of the pipe (for a given pipe with the same gas moving through it, A₁V₁ = A₂V₂), thus changing the diameter of the pipe will surely change the flow rate (the narrowest part of the pipe will dictate the flow rate due to the bottleneck it causes). Also, the flow rate is related to the opening of the pipe. In this case, the opening would be the air filter, which surely causes a bottleneck over having a wide-open end. Changing the length will negligibly affect the flow rate, as once the air is used by the engine, it leaves an empty space which is then filled by more air in the pipe, pushed in by the force of the atmosphere. To prove it, you could take a pump with the inlet connected to a reservoir of a given volume of fluid. You'd get different lengths of the same diameter tubing and time the time it takes for the pump to empty the first reservoir, and what you'll notice is that the time it takes will not change no matter how long the tubing is. The given volume of the fluid divided by the time is the flow rate of the pump (in the units you used before: (cu. ft.)/(min)).

I'm not trying to deny what you're saying, but I just can't wrap my head around it and am debating for the sake of my own curiosity

edit: Where does the 14.7 come from when you use 14.7/A = P? You didn't give units, but I assume you mean 14.7psi. That's entirely a false equation, because psi (lbs./sq. in.) is a unit of pressure, not force. Thus, you'd plug it into F/A=P for P, and not F.

This post has been edited by solidxsnake: Jun 25, 2010 - 10:39 AM

Has anyone ever tried a cowl-induction intake? I've been trying to come up with one but there's just too much stuff in the way and I'm budget limited.

I know people in the Miata community have had great luck with a cowl intake. Sort of like ram air, it pulls air from the high pressure zone in the cowl.

I've never seen that before, looks really cool. Wonder how it performs.

Google Randall Intake, it'll come up with all sorts of stuff. It just ran straight into the stock filter box, according to Flyin' Miata's dyno results they got 5hp to the wheels on an all-stock 1.6 motor with that intake, running a 5mph fan blowing air over the car to simulate driving conditions.

I'm working on a design for the Celica. I'm going to take my cowl off later and measure where it would need to be to fit, and make sure it wouldn't sit low enough in the cowl to suck up water. May try to ghetto-rig something up with some materials at work to experiment with later today.

QUOTE (hatchy_gt-s @ Jun 17, 2010 - 11:58 PM)

You dont loose pressure if you lengthen and decrease diameter. If I have something that is 14in long and 3in diameter that gives me 99 cubic inches , and if I extend it to 18in with a diameter of 1 3/4in it gives me 99 cubic inches of volume. So if I have the same volume I have the same amount of pressure.
The equation for Volume is;
Pi x radius squared x hight
or Pi*r2*h
or 3.14*r2*h
The equation for pressure is;
normal force(14.7)/area=pressure
or F/A=P
or for cars 14.7/A=P
The only thing you change when you change length is distance ie the time it takes to reach the car.(I dont think you really want me to get into the math of that to)

your equations apply for fixed mass (closed) systems (ie. tanks, piston cylinders, etc.).. but pressure changes in intake systems work differently as there is continuous flow (fixed volume or open systems) so you'd need to use flow energy equations (Darcy-Weisbach equation). more info


h = pressure loss, f = friction factor which is a function of the Reynold's number & inner pipe surface roughness & pipe diameter, V = flow velocity, g = gravity, L = Length, D = Diameter

reducing the length or increasing the diameter will reduce the pressure loss

btw, it's F/A = P = 14.7 psi, not 14.7/A = P

This post has been edited by azian_advanced: Jun 25, 2010 - 5:58 PM

Agh, friction, you bitch! That makes a lot more sense, I figured disregarding friction would be acceptable since the losses would be negligible.

Fluid dynamics are not my strongest point.

thats pretty sweet, deff. update us with anything you do

You should put an intake right out the top of your hood, taller than the car itself. It'll make 200+ horsepower easily.

All this talk and arguing over equations only to add a max of 5hp to an N/A car. O well, good info nonetheless.

No, you should run a pipe from the intake manifold through the front bumper so it juts out, and connect it to the exhaust of a vehicle conveniently placed a few feet in front of the car. Engines release exhaust gases, right? Now you'll be releasing MOAR gas, which can only translate to MOAR power.