CFM's on Fan

ajracing · #1 (**permalink**) 05-12-2010, 06:51 AM

can anyone tell me how I can figure out the cfm's of my fan? It's a 16" straight blade w/a pitch. There are no markings anywhere on the housing.

Aj

kitcarbp · #2 (**permalink**) 05-12-2010, 07:14 AM

Without using or building a fan dyno its hard to get precise numbers. However, to get you into the ball park, current consumption is one indicator. Fan manufacturers (good ones anyway) rate their fans based on the restriction they see in the application, this is usually a chart or table with CFM's versus static pressure ( mm or inches of water). A example from a reputable OEM manufacturer is shown here where thye are kind enough to include current draw as well. The air flow are in SI units or cubic meters per hour but you get the picture.

In ball park terms , no fan will see zero restriction (0 static pressure) when mounted on a rad. in an automobile.

But cfms are near proportional to current draw in amps (roughly speaking). If you measure about 10 amps at the fan, you are close to 1,000 cfm, 20 amps; 2,000 cfm and so on. Its easy to measure current draw at the fan with a good auto grade current meter. Almost forgot, make sure you know the test voltage, most fans should be checked at alternator output voltage or 13V as a standard, easy to do when engine is running. Your wiring/relay must be top notch to support a good fan. Good luck in your quest and when in doubt, use a high quality fan with known performance, your engine is just too expensive not to.

undy · #3 (**permalink**) 05-12-2010, 09:01 AM

2000 cfm, +/-

ajracing · #4 (**permalink**) 05-12-2010, 11:43 AM

sounds like I may need to replace. any suggestions on brand. How are the SPL ?

RICK LAKE · #5 (**permalink**) 05-12-2010, 01:28 PM

ajracing AJ any where from 1,600 cfm to 2,400 cfm's. The big thing is do you have a schroud around it to force the air through the radiator? Most cobras are running a 16-18" fan. You also have to remember that over 45 mph the air coming in the opening is as much as what the fan can pull. Alot has to do with the angle the radiator is set at. ERA has a deflector for their cars because of the lay back position and wanting to get as much cooling as possible of the radiator.
Do you have a over heating problem?? How thick is the core of your radiator? 2,3,4,core deep? Rick L.

ajracing · #6 (**permalink**) 05-12-2010, 02:08 PM

it has 8 fins, i believe. angle is about 30 degrees.i have an irregular temp. change. as i am changing out the water pump, t-stat, hoses and cap, i figure why not change out to a better working fan.

undy · #7 (**permalink**) 05-12-2010, 05:29 PM

90 to 95 3.8L Ford Taurus fan. Better make sure your electrical system is up to snuff.

coupeute · #8 (**permalink**) 05-12-2010, 09:04 PM

Check with Jack Mattson, The electric fan Guru. His toll free number is (866) 435 6477 and his web site is " The Fan Man "

RICK LAKE · #9 (**permalink**) 05-13-2010, 04:29 AM

AJRacing AJ we need to talk before you start doing all this changing about your temp drops. It could be normal. I run a 180 stat and get a 30 degree drop in about 3 seconds when my stat opens. Race for 20 minutes and the temp is 185-190f. There are a couple tyles of water pumps, you want a hi flow or A/C water pump. If the fan does have a schroud you are looking at a 20 degree different in temp alone. The other thing is having some where for the hot air to go. I crack the back of my hood when the car is hot to help remove the air. Lets talk. Rick L.

sllib · #10 (**permalink**) 05-13-2010, 06:55 AM

Since you're driving a Unique, assuming it's fairly stock, you probably have a Spal fan. There is only about 2" of clearance between the radiator and the sway bar and Spal makes a slim fan that works well in that space. If this doesn't work for you try posing your question on:
www.uniquecobra.com.