Is there any difference between putting the rad fan on the front and blowing through, or on the back sucking?

Regards,
Dave

Hi
Think most will say behind and suck is more efficient, as the fan itself doesnt disrupt the air flow.

Nick M

Mine are suckers

I can't remember where, but I seem to have the figure of suck throughs being about 20% more efficient in my mind. It makes sense, as Nick said they don't disrupt the airflow that way and so you have more lamina flow over the fins.

The front mounted "blowing" fan is operating in cooler, therefore denser air than the rear mounted "sucker".
Shouldn't that increase its efficiency?

I cannot find it, but a long, long, long time ago I used to wear a T-shirt with a picture of a big, supercharged, American V8 on the front.
Below the picture the legend read;-

"I'd rather be blown , than injected !

[Edited on 26/3/15 by slingshot2000]

The fan causes a hell of a lot of turbulence and generally messes up the airflow, which reduces heat transfer from the radiator (you want a nice smooth flow). If you suck in the air it remains smooth until it hits the fan - that's also why wind tunnels suck through rather than blow through.
There may be another mechanic at play here, but that's what I can remember

Also the density of the air doesn't overly affect flow through the fan - I'd imagine the change in density is relatively small compared to the flow through the fans.

Best option for this situation is rear-mounted with a cowl around the fan and the blades a small distance from the rad surface.

Too close and you get a lot of "chopping" noise.
Too far and you suck air in around the fan not through the rad.
Cowl increases fan efficiency by a LONG way.

That said, front mount might affect efficiency but the bulk of your rad surface will be free of fan effect and when you're moving >50mph the airflow from the car will out-perform the fan anyway.

If you can't fit a cowl to guide air into the fan, put the rad in front.

[Edited on 27/3/15 by coyoteboy]

Mine is behind the rad, and for the only reason is that I believe it looks neater looking through the grill at the rad
plus in theory the airflow is constantly on the front rad surface while moving and not restricted in any way
also the fan should not really be coming on in normal instances

Ive got a new Revotec 12" slimline sucker going cheap if interested.

One of things I did to cure my overheating was convert to rear mounted fan