Over the years I've seen many threads asking the best/correct way to fit a FMIC, slimline fans and rad combo and there's always mixed responses/opinions.... Fans then IC and rad, IC then fans and rad, IC, rad then fans, etc..
A couple of weeks ago I was mapping an RST with an Airtec IC, Spal fans and Airtec radiator... fitted in that order, the setup was far from optimal so I thought I'd share my experience with you and try to explain why it wasn't good and show how to do it better, hopefully giving anyone that might need to know some useful info!
The first issue I had was high intake air temps (IAT, ACT, MAT), once the car was up to normal running temperature it was at 35c and after only three or four full load WOT runs it was at 60c and detonating like mad, even cruising at 50mph in 5th to let it cool down only brought it to back 55c.... this of course was terrible!
There was no way to map around such high temps and I ended up with only about 16psi of safe boost which was very disappointing as the car had so much more in it.
The second issue was coolant temperature, it was hitting 120c and struggling to come down without the use of the cabin fans!
It was obvious at this point that airflow to both the IC and rad was not good!
So here's the problems...
First off there was very little IC surface area exposed to full air flow, just the small area you can see though the upper opening in the bumper, the lower one just exposed the end tank which is no help at all.
Then having the fans in-between the IC and rad creates two problems, air will always take the easiest route so having a huge gap between the IC and rad means what air flow you do have will take any other route it can instead of going through the fans and rad, the fans themselves actually cause a restriction blocking air flow to the rad (Remember your fans do nothing to aid cooling other than when your car is stationary or barely moving).
In addition to those problems the fins on the IC run top to bottom and the fins on the rad run side to side effectively blocking each other if they were installed back to back (this is crazy as they are both Airtec items and should be designed to work together?!
).
Finally the bonnet has been raised to facilitate using an EFI inlet on a Zetec and this totally ruins the airflow through the engine bay (No it does not aid cooling), again the air will take the easiest route out of the bay basically avoiding the rad as it's much harder to flow through than just going around and out the back of the bay.
The most efficient install (and how you'll find it on most OEM cars) is to have the IC almost flush against the rad ensuring the fins line up so that air can flow through both uninhibited (using draft excluding foam/tape to seal the sides and top and bottom where they line up makes a big difference too, but most RST IC/Rad combo's don't allow for this as they are not the same size), then install the fans on the back of the rad creating an area of low pressure ensuring that air is sucked through both the IC and rad, ideally a fan shroud would be used but I've not seen anyone that offers them.
Here's a picture showing what I mean, it's not for an RST and it's not perfect as about 25% of the rad will see no airflow when relying on the fans but you get the idea.
A heat shield of some sort to protect the fans from the turbo may be needed if you do not have much clearance (most don't), heat tape, turbo jacket, etc.
I hope this is helpful to some of you seeing high temps (both coolant and intake air) or to anyone about to install a FMIC etc.
With the bonnet shut properly most cars can actually get away with sub-optimal installs but it's still good to know how to do it for the best results!
