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Author: Subject: Radiator size

posted on 22/2/17 at 08:05 PM Reply With Quote
Radiator size

Q about radiators.
I understand that the length and hight is important for cooling. The bigger they are the better.
What about thickness, is it also the thicker the better cooling?
Is there some literature about it?
I have room for 50 cm wide, 40 cm high and 12 cm wide.

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ian locostzx9rc2

posted on 22/2/17 at 09:27 PM Reply With Quote
Yes the thickness makes a big difference as it has a bigger capacity and cooling area
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posted on 22/2/17 at 09:31 PM Reply With Quote
generally the thicker the better.
but its more about the cores (pipes) running through, again the more the better
most modern aluminium rads with plastic sides are good

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posted on 22/2/17 at 10:00 PM Reply With Quote

Yes, thickness has its importance too. It increases the exchange surface between the cooling air and the surface of the tubes containing the coolant.

But it is not as simple as that. Cooling capacity depends on a lot of factors, like air flow, construction matériel of the radiator, tube material thickness, louvered fins or not, and more... Not only the core's size.

If you are not a fluid engineer, try to find some info about other users who are using the same engine/car/application as you, and their experience, and you will find your rad. But don't go for the biggest radiator you can fit, it might be overkilled : don't forget that the bigger the radiator is, the more coolant it contains, so the more weight you will carry. And here, we are talking about litres, so kg's !
And there is a point where size no longer matters , which means from that point, if you increase the radiator size, you won't get any cooling benefit. You will just carry more coolant, so more weight. So, like everything, the radiator choice is mostly a matter of compromise.

In my pas career, I saw competitors trying to gain every gram they could on wheels, brake, seats, bodywork, even brake hose and fittings, and then go for an OEM copper radiator, very heavy, and carrying 5 litres of coolant or more, when an custom made aluminium one, much smaller and carrying much less coolant, so much less weight, would have been enough. I'm sure people involved in motor-sports part retail business can second me on that, and have had the same experience.

Try to ask PWR or Pace Products what radiator size would be suitable for your engine/car/application, you will be surprise how small it can be if you use the best engineered radiator. Of course, it is not the same price as an OEM rad, but you get my point : size is not everything, and it can be an issue because of the coolant weight VS cooling capacity.

As said above, if you go for OEM radiator, chose an aluminium one, which is known to cope with your engine size/power. For example, I have a Mercedes 190E radiator in my Haynes Roadster with a Sierra 2,0i DOHC. I drive my Roadster in the south of France, where I moved back last year and where it is pretty hot, without any cooling problems. People racing with Zetec's have are also very happy with this radiator. It is in aluminium, compact, but thicker that Clio/Polo/etc. rads. And the core of this rad is just 290mm x 348mm! The original Sierra 2.0i DOHC rads were much bigger !

Hope that helps


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posted on 23/2/17 at 07:21 AM Reply With Quote
I was asking this, because I'm rebuilding a Bonito, VW beetle floorpan.
The engine is in the back and I put a Subaru 1800 turbo in it.
Most of these cars have a radiator in the front with tubes underneath the car, and you need to cut holes in the front and the bonnet.
I like to put the radiator in the back, next to the engine.
So I thought, maybe a thicker one will do the job.
There is an air inlet on both sides of the car, one I use for the radiator, the other one for the air intake engine.

At a normal car, the fan blows the air over the engine and it goes out at the under site of the car.
So I guess, when I place the radiator obliquely, maybe 45 degrees on the side, the air will be forged out.

[Edited on 23/2/17 by kitman]

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posted on 23/2/17 at 07:33 AM Reply With Quote
My collection of parts to build my car came with an OEM single 32 core radiator which I ditched in favour of the kit manufactures twin 27 core "Coolman" same size as the single core, same tank size but thicker core because of the double line of tubes.
After a considerable bhp increase I swapped out to a Boston radiators 40 tube twin core again with the same size/area which gave more cooling.
Whilst the radiator area and water capacity is important there are also other mitigations such as blocking the gaps around the radiator so all the air goes through the radiator not round it.
The fan is on the rear not the front although this has a small benefit.
The hot air can exit the engine bay easily, a common problem with 7 type cars.
An alloy radiator cools better than steel/brass.
A lower temperature opening thermostat.
A pressurised header tank.
Proper antifreeze mix.
An oil cooler.
An interior heater matrix which you can build into a side pod and use a heater valve to switch it on.

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