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View Full Version : Downflow vs Crossflow Radiators - Q


WanaGo
01-10-2008, 06:43 AM
Hey,

Done a bit of googling about radiators, but one question remains.
Can a downflow radiator be mounted on its side, and function as a cross flow ratiator - if the cap is relocated onto the pipe, rather than on the top of the tank itself?

Or is a crossflow radiator actually totally different, and there will just be airlocks/problems if this is done?

Obviously I am trying to figure out the best cooling for my mini, and I see both types are readily available - but downflows are quite a bit cheaper.

A crossflow radiator should work out for me, as I have quite a bit of width to play with if I start going under the guard - its just the height I am a bit restricted by, due to the design of my front gearbox mount on my b16a2. And obviously cross flow radiators are generally shorter, but wider, due to the tanks being on the sides, rather than on the top and bottom.

Thanks
James

Geehawk
01-10-2008, 07:31 AM
IIRC Cross flow radiators usually have 'baffles' in the end tanks so that the water is forced through the cores rather than taking the easier route of through the tanks.

DarrenW
01-10-2008, 12:54 PM
As far as I know, there is no difference in design really.

So you could just swap them over, if it is a non-capped radiator. :P or clearly weld up the hole :shock:

Neither is more effective from the research and the people at radiator places I spoke to.

Crossflow design came about on moderner cars, coz they have a lower bonnet line, nothing to do with cooling capacity. :wink:

I swapped to a crossflow design and managed to increase the cooling area by about 6% IIRC, for the same external measurements, as the size of the tanks became smaller.

Normally the most important parts are:-

1) Finned SURFACE area, more is better
2) Airflow though the radiator

Then other factors:-

1) Row setup(for instance I swapped to a better core, that is 1 row of 40mm, from a 2 row setup of 42mm IIRC)
2) Number of fins per inch
3) Material it is made from(ally is not the best but is lighter)
4) blah blah blah ZZZZZzzzzzzzzzzzzzzzzzzzzzzzz :lol: :lol: :lol:

Hope that helps :P

WanaGo
02-10-2008, 02:42 AM
So you dont think there is any problem with mounting a downflow one one its side?...

interesting...

Cheers
James

madeinnz
02-10-2008, 03:55 AM
heres my 2 cents worth :either can be used BUT if the outlet and inlet pipe are on the same side in a cross flow radiator you will require baffles in the end tanks to direct water flow across the tubes otherwise it will just go in one pipe and out the other hope that helps :lol:

WanaGo
02-10-2008, 04:49 AM
heres my 2 cents worth :either can be used BUT if the outlet and inlet pipe are on the same side in a cross flow radiator you will require baffles in the end tanks to direct water flow across the tubes otherwise it will just go in one pipe and out the other hope that helps :lol:

yep thats right.
If the pipes are on the same tank for a cross flow, then that generally means they are a dual pass radiator, where there is a baffle in the tank.

On a downflow mounted sideways though, it shouldnt have that problem as the inlet and outlet are on seperate tanks, but will the water flow properly? It will just be a single pass radiator I would assume if this was done.
To make it better I assume the inlet and outlet should be moved so one is at a top corner, and the other is on the other tank and on the bottom corner? so water will need to flow the largest distance through the radiator to get out...

Thoughts?

Cheers
James

WanaGo
02-10-2008, 05:20 AM
This is the sort of Radiator I was looking at.

http://images.trademe.co.nz/photoserver/tq/96/70633396.jpg

Core size:450*398*56 (HxWxT)
About 480mm high incl top of the cap, and tank to tank is 500mm (from what I have been told)

Still have to measure up when my mini comes back from Paint...

Cooling wise, should be ok for b16a2 I think...
I think stock honda ones core are about 350x350x16 or something.

Ta
James

DarrenW
02-10-2008, 08:27 AM
Ideally the inlet and outlet, should be on opposite corners for certain on either setup.

The guy at radtec reckoned that it would be worth about 2-4 degrees if they werent(irrelevant if downward or crossflow and ignoring any 'baffle' within the end tank to push water to the ends of the end tanks, that IIRC some of the really old car radiator have)

Surely the picture above, is a dual pass radiator ?

Why buy one, surely it isnt that much more to get one made up to your specs? :? :oops:

WanaGo
02-10-2008, 08:30 AM
yes the one pictured is a dual pass radiator.

Dollars wise, that is about $340NZ - which is about 130GBP at todays rate.

To get a custom one, it will be around 500NZ - 190GBP.

Whereas a downflow one is about $200NZ for a full alloy one.

DarrenW
02-10-2008, 08:46 AM
I am suprised over the price difference :shock:

I would suggest you ask them, why there is, if the core size is the same?

Also tell them what you intend to do and see what they say.

Would seem to suggest there is a reason for it.

pritch
02-10-2008, 03:34 PM
would this rad be any good? the one mini tec supplly for the mtb2 subframe is just a civic rad with the outlet pipe repositioned further across? http://cgi.ebay.com/ebaymotors/92-95-96-98-Honda-Civic-MT-Racing-Aluminum-Radiator-NEW_W0QQcmdZViewItemQQ_trksidZp3286Q2em63Q2el1177Q QhashZitem180295225696QQitemZ180295225696

Slugman
02-10-2008, 11:07 PM
Sorry to tell you this WanaGo - I got PWR to make one for me (High flow Aluminium blah blah blah) & it came to $650 delivered.
You are about the same distance away so transport should be about the same depending on import duties. Mine is 400mm wide by 395mm tall, & 57mm deep. It just fits, with some metal cut out of the clubman (The flat bit under the grille) but I have the tanks top & bottom, & it wouldn't have fit at all if the tanks were on the sides. (It would hit the headers - Even then I have to put it in on an angle to clear the pipes, then once the bottom tank is past the header pipes, swing it around to get it straight.) 395mm tall allows the rad to fit between the crossbar at the top of the grille & the top of the Watsons subframe, with a bit of the crossbar cut away to allow the Rad-cap to poke through. There should be pics in my build diary thingy that show where my rad goes.

Oh, BTW - I had to lose the bonnet catch & go to bonnet pins, as the rad got in the way. I managed to keep the safety hook though.

Maybe just get a Civic Rad instead? It's hot up here, so I needed the biggest aluminium one I could get, but you should be cold down there. :?

WanaGo
02-10-2008, 11:47 PM
would this rad be any good? the one mini tec supplly for the mtb2 subframe is just a civic rad with the outlet pipe repositioned further across? http://cgi.ebay.com/ebaymotors/92-95-96-98-Honda-Civic-MT-Racing-Aluminum-Radiator-NEW_W0QQcmdZViewItemQQ_trksidZp3286Q2em63Q2el1177Q QhashZitem180295225696QQitemZ180295225696

Yeah these are the common ones available here too, which are about $200NZ. Just dont think I can fit one due to the front gearbox mount. Will have to make a cardboard radiator and try when I get the mini back from paint.

WanaGo
02-10-2008, 11:50 PM
Sorry to tell you this WanaGo - I got PWR to make one for me (High flow Aluminium blah blah blah) & it came to $650 delivered.
You are about the same distance away so transport should be about the same depending on import duties. Mine is 400mm wide by 395mm tall, & 57mm deep. It just fits, with some metal cut out of the clubman (The flat bit under the grille) but I have the tanks top & bottom, & it wouldn't have fit at all if the tanks were on the sides. (It would hit the headers - Even then I have to put it in on an angle to clear the pipes, then once the bottom tank is past the header pipes, swing it around to get it straight.) 395mm tall allows the rad to fit between the crossbar at the top of the grille & the top of the Watsons subframe, with a bit of the crossbar cut away to allow the Rad-cap to poke through. There should be pics in my build diary thingy that show where my rad goes.

Oh, BTW - I had to lose the bonnet catch & go to bonnet pins, as the rad got in the way. I managed to keep the safety hook though.

Maybe just get a Civic Rad instead? It's hot up here, so I needed the biggest aluminium one I could get, but you should be cold down there. :?

Cheers
There are local firms here who make custom ones, and I have a few quotes for different options.
Just trying to find options for one already made that may fit.

I think I will go down the path of making a cardboard one and see what size I can get away with.
Dunno how the front of the Watsons frame differs from mine, but that will govern the height.

Cheers for the info

James