I basically have an electric slimfan that flows 1250cfm, I was thinking of putting this fan on the back of my stock mount intercooler to help keep intake temps down. My question is what does 1250cfm equal in relationship to air speed going through the intercooler in mph? I know this fan while help putting around in slow moving traffic, but could it possible help while moving as well?

 

There is a lot more to figuring something like this out than you might think. The biggest variable is how much air coming in the front bumper actually makes it to the intercooler core and how much faster/slower this air is moving compared to when it first entered the bumper (very dependent on ducting). Then there is the frontal area of the intercooler and how much of this area is open space for the air to go through. So there is no good way to say...here, use this relationship.

I would say it will definitely help in traffic and will help while driving at slower speeds depending on how bad your ducting is.

 

You could do a rough mathematical estimate by measuring the area of the fan input then use that for forward measurement calculation.
If fan input area was 2 sq ft, then: 1250 / 2 = 625 feet per minute. Convert this to mph.
This calculated value would be if there was 100% efficiency, which there isn't.

Years before Mazda changed the RZ air inlet due to blowing engines on the track due to hot back flow through the IC into the engine,
I calculated and posted this problem here.
That led to me modifying mine which ended up being what Mazda later did.

 

Thanks for the replies. Yeah, I figured the performance would be better considering how small the duct opening for the large stock mount is. The fan is a 14 inch puller type that covers most of the intercooler (probably about 2 inches open on each side). I'll try to do a rough calculation and figure it out.

 

In my experience, a properly applied fan is a win--win. The fan being a restriction is just a lot of hype at the velocities, flows and efficiencies we can achieve--assuming a properly sized, propeller type fan such as we generally use.

In the example above, at 625 fpm, the velocity is going to be (625 fpm * 60min)/5280ft = 7.1mph, assuming no losses as was pointed out. The important point here is that a few mph is sufficient flow to establish a significant cooling effect. More speed (thus airflow) improves cooling efficiency, to a point, but it is not a linear relationship; rather one of diminishing returns.

During movement, what the fan does is effectively reduce the static pressure behind the IC and promote more flow through the IC.

 

Ahh, sounds good...this is very promising then.

 

Well it made a difference in traffic, but was barely noticeable on the road. I guess the hot air being pushed from the radiator fans is too overpowering. I'll probably just buy a vmount setup or try to get someone to custom fab my current system into a vmount.

 

How is it ducted? If it is ducted poorly, it doesn't matter what you do, it's going to perform poorly. With proper ducting the hot air from the radiator shouldn't pass through the intercooler at all.

 

It's ducted properly, at least this is the duct that came with it...even has a rubber grommet seal between the duct and intercooler.