How many CFMs do I need in an electric fan?

[ClayW]

Looking at buying an electric fan setup and I'm curious how many CFMs I need to properly cool the NA motor.

Also, can I just add up the CFMs from two fans if I mount them side-by-side?

I'm trying to figure out a solution to wanting an electric fan while keeping all my A/C stuff. I figure that I might be able to stagger two electric puller fans so they won't interfere with the water pump pulley.

[Harv]

I don't know about how many CFM's are required but I have noticed that the Summit catalogue lists them in how much HP the motor makes. I also see that they make some pretty slim ones that may fit in front of your rad and AC stuff.

John

[KFunk]

I think mine is around 1200 CFM, and thats with a brass/copper 320i radiator.... works pretty darn good. Mine sits in front of the radiator. I think it might be a proform fan from Summit Racing.

[BLUNT]

im running a 14 inch spal curved blade. if my memory serves me the curved blades make more noise but push more air. i do not recall cfm. i was going to say 3k until kfunk posted 1200 cfm. i may be mistaken. but mines a pusher and i have a/c up front. it just barely fit thru the opening.

[ifayeoh]

Its gonna be real tight to fit two in there. they would have to be 10 inch fans or maybe even 8 inch ones.

Maybe if you want two, put a 14 as pusher and a 8 as a puller on the lower right, having the 14 turn on when AC is on and the 8 come on when the engine needs it, will a tight fit as a puller as well. just a thought. Not sure if the 14 is enough to cover both needs. depends on climate and such i would imagine.

yes you just add up the cfm's,

[DanOKC]

I don't have an electric fan yet, so I can't comment on CFM's, but E30 & E28's use a fan with a relay across a 25 watt or 50 watt resistor to achieve 2 speed operation, so if you can put in an electric T-stat, you could have 2 speed fan operation. There are also aftermarket PWM fan controller boxes if you want to get fancier than just a relay & a resistor.

[Pinepig]

A 12 inch slimline with about 1200cfm or better will do it as long as everything else in the cooling system is OK. I get by with the 1200cfm slimline style one with 105 deg temps around here but have the big IE aluminum radiator. I also loose a bit ( of fan efficiency ) with the intercooler in the front and the fan sandwitched between.

I'm using this one bought from him also, good guy to deal with.

http://www.the-fan-man.com/shop/size-push-part-0505-p-201.html?cPath=33

[ClayW]

im running a 14 inch spal curved blade. if my memory serves me the curved blades make more noise but push more air. i do not recall cfm. i was going to say 3k until kfunk posted 1200 cfm. i may be mistaken. but mines a pusher and i have a/c up front. it just barely fit thru the opening.

This one?

It's a 14" curved-blade SPAL pusher fan that makes 1720 CFM.

So, you have one of these in front of your A/C condenser with no mechanical fan and it does the job?

[Beaner7102]

I run a 12" pusher fan on a manual pull switch. I only need to turn it on after sitting in very heavy traffic for 5-10mins (gauge halfway between red zone and 3 o'clock). I find even traveling at 25mph there is enough air flow through the rad to keep the motor cool (gauge at 3 o'clock) without the fan on. HTH

Beaner7102

[jimk]

Rapidcool 14", as per their catalog for the 4 cyl BMW, I believe it is 1400 cfm.