Fans blowing in, or out??

[craig-ultima]

I'd recently posted proudly that I've never had an overheating problem, but I had my first today.

The problem was that I joined a parade of about 1000 cars in a local car show that crawled for maybe 2 miles slowly (walking pace, or slower) through a local town. The air ambient temperature was 80F, so quite warm. I was dying in the cabin since my AC is still not gassed up. Cabin temp was about 120F since the sun was still out - at times I crawled along with the doors open to get the cross-breeze.

I've been pulling down all the posts on over-heating, so thanks for all those extra hints. I'll do the upgraded radiator fans and maybe an electric water pump in addition to the mechanical pump... But here is my additional question:

I have an oil cooler on one side pod vent, and the AC condensor on the other side pod vent. The AC condensor has a fan on it (no idea which way it runs, since I haven't run the AC yet). The oil cooler soes not have a fan on it, but I could put one on easily.

My question is: should I wire these fans to blow in or out of the car? My heating problem is only in traffic jams where the car is basically at standstill for prolonged periods. My thinking is that I should wire the fans to suck air out of the engine bay and out the side-vents (hopefully sucking cooler air from the road surface to run through the oil cooler and AC condensor), rather than drive extra heat into the engine bay.

I'd very much appreciate comments on this. Is the best way to cool the engine to suck hot engine-bay air out through the AC/oil to the outside, or to suck ambient air in fronm the outside, heat it through the AC/oil then blow it over the engine then out the back of the car.

Thanks,
Craig.

[cortina1]

hello Craig,

although fans will mostly kick-in and run while you sit in traffic, what would be the situation when they kick-in while you are moving? If you have fans attempting to blow against the natural air-flow path would rekon their effeciveness would be way down- would suggest that you set them up to allow for a moving car.

[DHGTR]

hi craig,

dont forget that the oil cooler and aircon cooler are meant to do just that. if you are dragging hot air across them from the engine bay they wont be doing any cooling. the fans must draw cooler air in from the outside of the car.

dave

[GreenV8S]

The fans should always be set up to blow the air in the same direction it will go when you're moving, otherwise you end up with a 'no-go' region where the fans and the ram air flow cancel each other out.

[menostig]

Well from experience - blowing out works fine. My Sport used to have an overheating problem in traffic, never when moving, so I put an oil-cooler fan (less cooler, I'm not going to bother now, anyone want one ?) in the pod to blow out when the rad-fans come-on. This way the a/c fan sucks air in, the fan on the other side blows out, inducing some convection current across the engine. No air comes in the vents when stationary so blowing out is not an issue. The side-vents on a Sport are flush so there's minimal air comes-in even when moving fast, in any case the temp comes down when moving and the fans switch off. Water was 80C and oil 82C all the way to Le Mans and back except for when queuing in towns and off-the ferry (in hot weather) when both stabilised around the 90 mark. I stood near the 'out' fan at one point and it was uncomfortably hot on my leg. For info this on a 360 bhp engine so if you've got lots more then that might make a difference though I doubt it at idle. Oh yeah, two other tips:
1) I replaced my 100C switch-on fan switch with an 88C one from Unipart for more proactive cooling (result - never touched the fan over-ride switch)
2) I set my warm idle to 1000 because this drops to 700 when the a/c is on full-blast (result - cockpit tunable idle to ensure less heat production in traffic)

cheers
Roger

[woodpecker]

Hi Craig,

I have also been reading all the threads on cooling and experimenting on the car, I upgraded the front fans and put a fan on the oil cooler within the side pod so it blows out-just like your proposing. I started by wiring this into the existing cooling relay but in the hot weather last week blew the 30A fuse. I have since re-wired it on its own circuit/switch and just use it if stationary. Seams to work fine and the canopy grp is a lot cooler as a result as well.

Next and final mod is to change the temp sender switch as per recommendations on this site so the front fans cut in automatically at a lower temperature.

Cheers

Steve

[GTWayne]

Hello Steve,just read your profile and saw that you have a proper coloured Ultima,well done,BLACK ULTIMAS RULE!

[craig-ultima]

Great. Thanks everyone. I'll setup the fans to blow in to start with and see how that goes. Good news is changing the direction is easy