zerogrip

I understand that CFM is volume/time----PSI is force/area but what happens if you connect an active blower (180cfm) directly to the intake manifold. How would this volume/force be measured?<ul><li><a href="https://forums.audiworld.com/a4/msgs/1370722.phtml">https://forums.audiworld.com/a4/msgs/1370722.phtml</a</li></ul>

Audiboy

For example - stand outside, grab a large, smooth, straight pipe, maybe 1 ft in diameter, 1 ft long. If the winds are moving at 1mph for example. Place the pipe in the same direction of the wind. Then to calculate how much air is moving, you can do the math. 1mph = 5820 ft/hr = 97 ft/min. Meaning in 1 minute, the air can theoretically move in something a distance of 97 ft.

Now take the volume of the pipe (phi* radius^2 * depth)= 3.1416 * (1/2)^2 * 1 = 0.78 cubic ft.

So, if the air can move 97 ft, and the pipe is only 1 ft long, theoretically, it can move in 97 ft long of pipe in one minute, so CFM = 97 * 0.78 = 76.2 CFM.

Now the question - what is the pressure? Now that is force. There is none with a straight tube. But if you block it on one side, then the air has to push through this blocking plate of area - phi * radius^2 or 0.7854 sq ft.

And if the earth is very determined to move the air through the tube, then it will start to exert force on this blocking plate which you can measure on the scale. If it registers 1 lb, then earth is determined to push 1 lb per 0.7854 sq ft of pressure, or 1.27 psi. Will earth do that? chances are no, the air will just stall in the tube - unless you modify the inlet of the tube such that it will collect air at a larger area with very little pressure and funnel it through the tube.

Moving air has some pressure because air has mass (density). It just depends on what apparatus moves that air.

So they are not quite related, unless you have all the variables. In your case, the properties of the fan, blade pitch, blade area, torque of motor, etc etc. I'm not an expert on this so I'll stop

zerogrip

While we are on the subject. I was thinking about doing an experiment with my new xtreme k&amp;n filter and a 180 cfm blower fan. It kind of reminds me of ram air or forced induction. I was thinking of placing the blower(speed controlled of course) directly in front of the k&amp;n. I would duct the intake to a cooler place for cold air. Of course with heat shielding, I think that the filter will be able to breath colder air in larger quantities giving me additional hp. What are your thoughts?

Here are some pics of the blower:
<img src="http://pictureposter.audiworld.com/40694/blower_side_view.jpg">

<img src="http://pictureposter.audiworld.com/40694/blower_top_view.jpg">

Electron Man

Surely you're not thinking of installing that under your hood.

Audiboy

from heat in the engine compartment of my little Mazda 323.

Here's the problem. Depending on what you are hooking it to, a 2.8L requires 311CFM at 6000rpm, a 1.8T requires 216CFM at 6500rpm.

Assuming it is a 2.8, and if the fan really blows only 181, then starting above 3500 rpm, the fan becomes a restriction - it may overspin but eventually friction will take over.

Two of those fans in parallel will blow the required CFM, but the current draw maybe too high, maybe 40 amps or more, such that the voltage of the car will reduce - depending on the alternator, and the energy to drive the spark plug coils will reduce, as well as the voltage on the fuel pump - fuel pump doesn't matter much because it is pressure regulated anyway. Also, the alternator will be heavier to turn at higher current requirements, although 40 amps won't hurt it much, maybe 1-2hp loss depending on pulley size, rpm, etc.

But those kind of fans don't work. The air can flow back easily through the blades loosing the ability to make pressure.

My 1.6L mazda required 177CFM at 6000rpm redline, so I pulled a fan like that from a FIAT A/C heater box. It worked for most of the rpm range and ~10% hp improvement was notable on a 2200lb car. It was funny though, although my friends didn't laugh and wanted one because I had mad boost yo with 0-60 9sec compared to stock 10+ and I beat most cars back then he he, including another 323 guy who asked me to pull over because he can't believe I smoked him bad

Have fun!

zerogrip

I was bored and had some extra parts and time. I believe that it is possible but the margin for error is so great. There are too many variables to consider. With the time in R&amp;D you may as well just but a PES G2. My initial goal was to make a custom intake using a K&amp;N xtreme cone filter and try to produce a true cold air intake. If you have any ideas please fell free to contribute. Thanks.

Vince

squidix9

rated at 180 CFM/atmospheric.

The maximum volumetric flow rate it can produce. This varies just slighly from the mass flow rate, not enough to worry about.

If you put it up against a restriction, you flow rate will drop, and the pressure will rise. You will have to see how much pressure you can achieve. You will find the the squirrel cage blower can deliver a lot of flow, but won't produce much pressure.

I've always wondered about doing something like that, just for grins, but never got around to it. I'm curious as to what you'll see.

Agent911

you got too many variables,

if you are eager and crazy - measure your intake valve diameter, and work out the total cross-sectional area to the cylinders.

now work out how long they are open per given RPM, and you can add your PSI to this to work out CFM.

or simply hook it up and run tests.

zerogrip

I may run some experiments. If I can pull colder air from the lowers with the blower into the cone, it may just be worth that alone. If there is compression and added hp, than thats even better. I will post results in the future.

Thanks

MNblackS4

You could always take a class in fluid dynamics.