ebow951

I noticed this section on the Delta Current Control site on selecting a cooling fan. I understood the paragraph on importance of fan selection, but they lost me when he switched to the mathematical analysis. I don't think I understand the point of knowing the CFM either, I don't understand how to relate that to the needs of the truck.

Anyone ever fill this out for any of our engines or know the stats? I'm driving a 22re myself, and planning on swapping to the Sable fan. Other than the fan diameter, I am at a loss.


The site: www.dcccontrol.com/0820.htm
Click the "Click Here" button on the top right until it gets to the fan control section.

Unknown Variables:
Vin: Input voltage
Iin: Average input current
Ipeak/Irun: Peak to average current (most oems:3 or 4, most aftermarket 2, Ramchargers 5)
Fan D: Fan diameter
Motor D : Motor diameter


Just curious ... love learning more about my truck.

ebow951

After staring at this thing for a while, moving on and then coming back, I think I figured a few things out.

Vin: Input voltage - Probably close to 13.6V on a 12V system

Iin: Average input current - I'm gonna go with 30A. Can't be more than 35 since the FK-35 is used by most.

Ipeak/Irun: I don't know this. OEM of 3 seems pretty good.

Fan D: A diameter of 16" for the fan.

Motor D: Could be two things: Straight up motor is 3", on the page he talks about the size of the blades. The inside blade radius is about 5-1/2"

That leaves me at guessing the fan pushes a CFM around 3500-3800*k. I still don't know what this means, sadly, and I don't know how it compares to the mechanical fan. Any thoughts?



PS ... I know this set up is recommended by a lot of people. Just curious about the math he's presented.

BigBluePile

iTrader: (3)

Hey man! I'm sure you already saw this, but here's what I'm using:
http://www.flex-a-lite.com/auto/html/black-magic.html


I don't know what my old clutch fan use to put out but this fan seems to work alot better. I've since upgraded it to a digital thermostat because the mechanical one is GARBAGE that comes with it. I'm also really good at rebuilding these fan blades too!

As far as the math...I have no idea...!

swaycleveland

cfm is the measurement of how much air the fan moves more cfm more air flow.
go get yourself a ford taurus fan and a flex a lite VARIBLE SPEED CONTROLER and be done ! the is a buch of write ups on the " taurus fan mod "
the taurus moves somewhere about 5000 cfm if i remember correctly
CFM cubic feet per minute

ebow951

Thanks for the advice guys!

I am already stocked for the Sable fan and DCC controller swap. I guess I'm more curios about the CFM stat. Specifically how much air is moved by our stock fan. I really don't have any idea how much air is needed to cool our engines under various conditions.

With so many write ups on this topic, I'm not worried about it working practically, just curious if anyone knew.

yota8083

I have heard that 1300 cfm will get the job done on a 22r/re so anything above that is gravy. CFM simply measures the amount of air pushed(or pulled) by the fan in cubic feet per minute. As for the equations.....

W=(1/2)mv^2 is the work produced by the fan. It makes sense that the mass of the air moved by the fan times the velocity of that air equals the work of the fan. It is simply the amount of air moved multiplied by how fast it is moved.

P=((1/2)(mv^2))/t is the power consumed by the fan during operation. Basically the amount of work done by the fan on the air devided by the amount of time the fan has done the work will equal the amount of power the fan consumes. This also implies that you can find how much work the fan produces if you multiply the power it consumes by how long it consumes.

A=D^2/1974 is simply the outlet area of the fan set equal to the diameter of the fan blade squared devided by 1974(probably a number found in a book). This equation by itself is not important but it helps you find terminal velocity which is important.

V=.932(cfm/D^2) is the terminal velocity equation. Terminal velocity being when the fan has reached its max push/pull at which the air is no longer accelerating. This equation multiplied by 1/2 of 1 cfm equals the power consumed by the fan. Think of this as the terminal velocity(max output of the fan)has a direct relation to how much power is consumed by the fan.

Reworking the last equation gives you cfm. I dont know if that helped you any but hopefully it makes a little more sense now.

Thomas

ebow951

That's great! Thanks Thomas. 1300CFM isn't a heck of a lot. No wonder it's important to have variable speed. Your motor would have a hard time staying warm if it didn't. Cheers!

BigBluePile

iTrader: (3)

Yeah, you wouldn't want your fan running constantly or else something is wrong. I know my fan, now that I've moved up here, hardley runs. It's been a long time since I've run my truck hard enough to really get it working.

ebow951

You had mentioned concerns about good areas to drive when I talked to you. Hope you're not taking it too easy. You've done so much work on the truck not to have a little fun with it. Family can limit your chances too though too

BigBluePile

iTrader: (3)

ehheheeh! I went this weekend and did some recon here on the island, we'll see. I need to take the thing out and see what'll do in the trails. I'd like to go down south and hook up with ol' algranger, but that's definately a day trip. I should hopefully be getting my '82 supra afm tomorrow and will start buying parts for that. Hey, do you have electrical readouts for that afm so I can check the guts to make sure it works right?

ebow951

http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

This should give you the info you need. Since the '82 Supra has the same guts as the 22re, the readings should also be the same.

BigBluePile

iTrader: (3)

Yeah, after I thought about it I was like: duh, plug-n-play...probably has the same readings dummy. I have an FSM and I'll look into it as well. Matter of fact my new AFM showed up today!!!