Skiniest Electric Fan

What the title says.  Looking for the skiniest electric fan out there.  I need one about 12" in diameter, puller, but interested in skinny fans in general, which may be of broader use here.

From some quick searching online, it looks like about 2" is the slenderest slim-line deal out there. 

SPAL 30100375

How well do you want it to work? Because skinny almost always equates to low torque which means low flow when actually attached to a heat exchanger. Is this for street use or track only?

In reply to Keith Tanner :

Track only.  Yes, I assumed skinnier = less flow.  The car in question runs fine at speed with no fan, so it's just needed for idle situations.  The SPAL listed above does ~860 CFM.  SOme of the thicker ones I've seen will do over 1000.  The desire here is to run a puller fan, as my understanding is that pushers tend to obstruct airflow to a greater degree, at least when not in use.  Of course, there's a lot less room between the radiator and the front of the engine.  So, either the radiator would need to go forward, the engine would have to go back, the water pump shaft would have to get shorter, or something really thin needs to fit in between.

EDIT: I've also thought of eliminating the mechanical water pump and going to a BMW-style electric pump.  The quick and dirty way to do that would involve simply cutting the impeller and pulley off a stock pump, basically leaving a stub shaft to seal, and than plumbing the e-pump in line at the lower radiator hose.

I was going to try to find the stuff that you posted about this recently, Keith. What thread was that?

IIRC those CFM numbers are badly hurt by actually trying to draw through a heat exchanger, and that's where the thin fans fall down much worse than higher torque models.

On the flip side, if we're only dealing with a radiator (no oil cooler, condenser, P/S cooler, trans cooler) that's a much less-bad situation, no?

In reply to Jesse Ransom :

Correct, radiator only, and a fairly small aluminum one to boot.  No other heat exchangers, manual transmission car. 

I don't have an easy way to pull up that recent thread, but it's true that only having one heat exchanger helps quite a bit. SPAL usually publishes a range of airflows for their fans depending on static pressure, so you can see how fast a particular one falls off.

This graph (which is in that other thread) illustrates it well - look at how the orange trace performs better at first but falls off faster as it has to work harder. 

One thing to consider - if your main obstruction is a factory water pump, it's probably located about the center of the rad. Can you run twin smaller diameter fans so you end up with the motors straddling the pump? Or is there more in the way?

In reply to Keith Tanner :

"One thing to consider - if your main obstruction is a factory water pump, it's probably located about the center of the rad. Can you run twin smaller diameter fans so you end up with the motors straddling the pump? Or is there more in the way?"

Thought about running twins or even a quad setup - you are correct about the water pump being the main obstruction.  Main issue there is cost, and how much would a little fan draw.  The radiator is fairly square, 12" high and maybe 16" wide.  I guess I could run twin 8"s, too. 

EDIT: just measured the core - 12-5/8" by 19".  The water pump pulley is exactly centered.  The pulley hub is about 3-1/2" wide.  There's 1-1/2" between the farthest forward part of the pulley (the 4 bolt heads that hold it on) and the back of the radiator.  So, perhaps a pair of beefy ~8" fans, or possibly staggered 10's if they'll work in the outline. 

The difference between the orange and grey setups in my graph is that the orange is a single big fan and the grey is dual smaller ones. If that helps your thinking.

SPAL has a fan with a belt driven offset motor. I used one with moderate success in a 514ci GTX.  Moderate in that it fit, but was not enough to cool the engine.

My personal rule of thumb is you need roughly 15cfm per horsepower, but this is also kind of nonlinear because of the effects of average horsepower. A 100hp engine might need a minimum of 1600 but be much happier with 2000, I have cooled a 750hp engine with a 4000cfm fan as a puller (2013 GT350 unit) and two 10" fans running full time as pushers, but it still ran hot when pushed a lot.  It had a very thick cooling stack too, which hurt.

The nonlinearity is that a lower power engine is going to be using a higher percentage of its actual power on a regular basis more than a high power engine will.

For sure, you will want something with shrouded blades, and nice curved blades not straight air-paddles.  A lot of Spal fans are air beaters, not air movers.

A lot of the muscle car restomod guys use the dual fan/shroud combo from Dorman specified for the Ford Contour.  Amazon/eBay used to sell them for about $110.  The dual fan setups offset the motors from centerline for better clearance around the water pump shaft.  

In reply to wawazat :

That fan setup looks to be about 16" high x 24" wide. A bit too big for my application, but good to keep in mind. Thanks. 

I found some 8" fans aftermarket fairly inexpensively, with curved blades, that advertise about 600 CFM each. Think I'll probably go that route.

I'm using two similar fans on my Dart, with a slant six paired with a much thicker than stock circle track radiator. The 10" and 12" SPALs are about the thinnest quality fans out there that you'll find.