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Thought I'd put this as a separate listing as it could interest other Subie fans,

I've had 3 radiators in my trike. An MR2 which was above the torque converter on an angle, a small Alfa 33 radiator that is hard to obtain in Oz now and a larger Alfa 33 radiator currently in the trike at the front.

I dont know if my method of calculation is roughly ok or not but the sizes of the Alfa radiators are- (L)x(H)x(thickness) all 1 row.

Alfa 33 large= 524mmx325mmx34mm I assume its 1 row. Roughly multiplying it all = 5790200

Smaller Alfa 33 radiator 545x234x32 = 4185600

Enter the Porsche 911 "centre" radiator. A long single row radiator only 170mm high.

The Porsche centre radiator 610x170x44 = 4562800

The small Alfa radiator worked well, cooled the motor adequately. I assume, as the Porsche radiator has a larger overall core area it would do the same.

This would enable me to mount this radiator at the rear engine bar area with 4 small 6" thermo fans on it. any thoughts esp my calculations

Um, sorry Tweety that figure you got there is the total volume in mm3, the more important one is the surface area to enable heat exchange, there's a formula somewhere that will give you that ( just have to find it ) ...

Cheers, Bantum ...

I'm onto it. thanks Bantum

Found a radiator size formula.

http://www.super7thheaven.co.uk/blog/wh ... -a120.html

Gotta convert mm cubed to inches cubed and cc also but came up with this

Porsche centre radiator is 4562800 mm sq based on core dimensions. 610x170x44mm. Subaru 1781 EA81 engine is 108 sq ".

Formula stipulates the following-

Start with 2 cubic inches of core for every cubic inch of engine. Increase or decrease that value by the following factors:

ADD

0.1 for a vertical flow radiator core
0.1 for an in-line engine
0.1 for a small trailer towing
0.1 for a 2 row radiator
0.1 for double evaporators
0.2 for outside temperatures of 105°F (40.5°C)
0.2 for a medium trailer towing
0.2 for a small engine fitted to a heavy car
0.2 for a radiator fan with diameter less than 90% of smallest dimension
0.3 for air conditioning
0.3 for no fan shroud
0.3 for an antique car with small engine compartment
0.4 for large trailer towing
0.6 for a diesel engine

SUBTRACT

0.1 for remote transmission cooler (not within radiator)
0.1 for standard in-line transmission
0.1 for a single row radiator
0.1 for a V6 / V8 engine
0.2 for a spacious pickup truck engine compartment
0.2 for outside temperatures less than 90°F (32.2°C)
0.2 for a full fan shroud
02 for a horizontal flow radiator core
0.3 for a large engine in a small car

In my trikes case-

Add- - 0.1 for small trailer towing, 0.2 for outside temp over 40 deg, 0.3 for no fan shroud, = 3.19
Subtract - 0.1 for single row radiator, 0.2 outside temp less than 32 degrees, 0.2 for horizontal flow radiator, = 0.5 = 2.69

2.0+0.6-0.5= 2.1

2.1x108= 226.8 area of radiator is 278 sq". Conclusion- radiator is 19% larger than required.

As a safeguard I can also add a small motorcycle radiator off the heater hoses if required.

I've done this on the aussieveedubbers forum. it is interesting because if we have a kombi van with two engine options the 2.0 litre EJ engine and the EA81.

Now for a Kombi. Lets say its for a 2 litre EJ engine. 2.0 litres = 122 sq"

We know the cubic inches of the Porsche radiator is 278sq ".

Lets say the outside temp stuff cancels itself out. Add - 0.2 for small engine in large car, 0.3 for no fan shroud, 0.4 for large trailer towing (this for it being a transporter load carrying vehicle etc) = 0.9 total added. Subtract- 0.1 for single row radiator, 0.2 for horizontal flow radiator... = 0.3

2.0 + 0.6 = 2.6.

2.6x 122 = 317. With the radiator being 278 sq" it is too small by 13%

What about a kombi with an eA81?

the 2.6 factor remains the same.

2.6x108 = 280. Radiator is 278. likely is ok for this engine.

Ok - interesting but the above is not what I was thinking ...

However this will get your head spinning : http://www.maplesoft.com/applications/v ... &view=html

Especially the Heat Exchange Equations ...

Cheers, Bantum ...

now, something is missing in the formula ... 0.7mm or 0.9mm 'gauge' of material used to make the cores ..... that will blow a good calculation !!

I just knew it wouldnt be a simple task. lol.

Bantum wrote:Ok - interesting but the above is not what I was thinking ...

However this will get your head spinning : http://www.maplesoft.com/applications/v ... &view=html

Especially the Heat Exchange Equations ...

Cheers, Bantum ...

I believe the people at maplesoft have way too much time on their hands.

That math hurt.

Tweety I like your formula it is simple, and basically says for every cubic inch of engine you need at least 2.5 cubic inches of cooling space.

I believe in the terms of litres a 2.2 litre motor would need around 7-10 litres of water to cool it. Thats with a single core radiator.

TOONGA

thats how I thought too. I recall the math for the supercharger and it was too complex for me but doable- just took me an hour or so. This one after a few tries was easy.