Radiator & A/C core positioning

[wagonist]

I'm sorting out some cooling issues with my project.
I've got a problem with clearance between the engine & radiator such that I can't fit any fans in there.

Would there be any issues with putting the A/C core behind the radiator so that I can put the fans in front of the rad?
Will there be issues with keeping the A/C cool as it will copping the hot air off the rad?

[river]

Hi,

You get more effect from the fans when they are pulling in air through the radiator core as opposed to pushing it.

If you are so short of space I assume the a/c coil will be very close to radiator? If so, there will be more resistance for the air flow as the fan attempts to push the air through the radiator and a/c coil.

The a/c coil will get warm when it operates and it needs to disipate this heat to be effective. The heat of the radiator will effect the a/c coil and mean it won't get as cold in the cabin. And, the a/c coil will impart heat into the radiator, which can raise engine coolant temp. Top this off with an inefficient pusher-fan and you'll have to be very careful with your design.

seeyuzz
river

[wagonist]

I really am that short of space.
I've got 35mm between the rad & the various pulleys on the front of the motor. Nowhere enough to fit a fan of any kind.

Most likely, the A/C will be bolted directly to the rad, how is this different to most other situaitons? The A/C core is normally in front & so would be more likely to impart its heat to the rad via the through airflow.

I'm not quite sure how a pusher fan can be much difference in efficiency to that of a puller? Except that it be pushing against stalled air.

I imagine the front of my project car is very similar to that of your AE71 (if it has A/C).

Personally, I only use the A/C to take the chill off rather than really cool the car. So I'm not worried about a bit of efficiency lost. I'm more a fan of the 4 & 80 theory of air con.

[river]

Hi,

Both the AE71 and the RA25 have air-con and the a/c coil is a few inches in front of the radiator. I've never seen an install where they were bolted together, let alone the a/c coil being aft the raditor.

A pusher fan will work, but I don't think it's as effective as a similar size shrouded pull-through fan. However, I could be mistaken on this one and there maybe someone more learned who is successfully running pusher fans on their system.

The radiator system is usually designed to take the extra heat from hot days and an a/c coil. I'm not sure an a/c coil is designed to cope as well with hot radiator air coming onto it.

There's no room in front of your radiator at all?

Also, can you not get thin electric fans?

seeyuzz
river

[wagonist]

No room.
There is about 35mm between the rad & the A/C core & then a little room in front of that, but I'm trying to squeeze a water-air intercooler rad in there as well...

Plus, I've installed a 2.0 DOHC motor instead of the original 1.8 SOHC, so its longer in front of the engine mounts (& no I can't move the engine back because I've got front driveshafts to worry about).

With the A/C core gone, there's an absolute crapload of room, but I'm not prepared to sacrifice it. If I was going to that extreme, I would've found a lighter & better configured car to start with.

[wagonist]

oh, and I'm already going for the thinnest fans available at 55mm.

[river]

Hi,

Pics?

Pic of front of radiator, behind radiator and inside the engine bay?

Oh, and what's the size of the a/c coil... length vs height vs depth?

seeyuzz
river

[wagonist]

Click on it to get a bigger version.

BTW, the upper support has now been removed completely to be replaced by a bolt on version.
Doesn't help that the rad shown is a custom one using 2 cores of the original car, so its about 60% thicker overall.

The A/C core is 600 x 300 x 20

[Dale]

I'd have to agree with river on most points, the fan pushing air onto the radiator or air con condenser isn't going to have the same effect as a fan set to pull air through. When it's pulling air through, it's forced to be drawn through the radiator (especially if shrouded), where as if it's pushing against it (even in a shrouded setup) the air will tend to try and escape through the route of least resistance, ie the sides and even push back against the fan trying to push the air through.

The air con condenser would be put infront of radiators more so because they don't have the same kind of heat to exchange as a radiator, the water coming out of engines will be 80+ degrees, and I can hardly imagine the refrigerant in air con systems reaching those kind of temperatures? So I'd imagine being behind a radiator it would be copping a lot of hot air, and be lucky to get cool the way it should.

Is there any chance of moving the radiator and condenser forwards enough to get a slimline thermofan on the engine side of the radiator? As you said the smallest fan is 55mm, and there's currently 35mm.. so it doesn't have to go forwards much to make it fit.

edit: Don't EA falcons or something like that have slimline thermofans? Some cars might come with slimline ones from the factory that you could retrofit, a wander around the wreckers might find you something close to being suitable.. or have you done that already?

[river]

Hi,

..... or mount the a/c coil somewhere else. All you need is the a/c pipes to it (which can be easily done) and one or two small fans to keep the air flowing through the a/c coil when the a/c is switched on. However... that's a pretty big a/c coil you got there and I doubt you'll find somewhere else to mount it in the engine bay.

seeyuzz
river

[Dale]

Elaborating on River's idea.. if it came to it and would solve your hassles, you could realistically get a smaller AC core from a different car and retrofit it. It would just be a matter of getting custom lines made up for it, which you may end up having to do anyway.

[wagonist]

Moving the rad forward isn't an option. The factory rad support doesn't allow it, and the bonnet catch sits snugly up against the A/C core.

I've been toying up with moving the rad backwards so I could sandwich the fans between it & the A/C core (but still in a push position for the rad though), but I gain the most space by having the A/C on the back (it fits under the power steer puley then).

It either that or I fit the intercooler rad back there & have the fans on the front of everything. Though I think this would negate the advantanges of havign the water-air setup instead of the top mount air-air interheater....

[BradW]

The air con condenser would be put infront of radiators more so because they don't have the same kind of heat to exchange as a radiator, the water coming out of engines will be 80+ degrees, and I can hardly imagine the refrigerant in air con systems reaching those kind of temperatures? So I'd imagine being behind a radiator it would be copping a lot of hot air, and be lucky to get cool the way it should.

Have you ever touched the pipes and condenser core of your A/C while it is running?
They get as hot, if not hotter than the radiator. The reason the condensor is in front of the radiator is to get sufficient cooling to effectively change the refrigerant from vapour to liquid. If this doesn't happen, the A/C will not work.

[Dale]

Clearly I haven't, and won't be touching them any time soon thanks to that little piece of info!

I should have thought more about my theory and how air conditioning works, but oh well. My mistake there.

[ProjectSleeper]

When I was re-doing my system with thermos - I spoke at length to a quite a few different Fan manufactirers, along with Air Conditioning specials and a couple of Radiator manufacturers and fitters etc as I wanted to get the best possible result to ensure maximum effeciency.

From my discussions, the BEST place for a Thermo Fan is as a "draw through" fitting as this is where the Fan is most efficient (even drawing through both a Radiator and Condensor). Swapping to a "push through" arrangement you can lose around 20% to 25% of the fans efficiency. If you have to push through both a Radiator AND Condensor, then the loss is even greater.(approx 40%)

Having the Radiator and Condensor as close together as possible is best for the efficency of the fan, however, a gap of approx 20-50mm (at least) is best for the Radiator and Condensor.

I am not sure of the project you are building, but have you thought about a combined Radiator/Condensor. These are quite unique, but have been made for certain vehicles that have a situation like yours where you just have to have both and space is very limited. They are very expensive, so you may want to re-think the options, but it can be done. There is an obvious compromise and if you are planning Nullabor crossings in Summer with the air conditioning on, then better you let people know where to find you - over-heated on the side of the road...