Questions about chilling 7800GTX SLi (-40ºC)

[Lord_RTKK]

Well, I will be doing some Dry Ice benching next days, and I will cool my 7800GTX SLi with water chiller, but it will be toooo cold (around -35/40ºC on the VGA core I think).
I want to use a Swifty MCP655 pump with Maze4 Acetal for 1 7800GTX and MCW50 for the other 7800GTX.
My question is if the 655 pump could handle those low temps, or it will crack or stop operating. Anyone have tried xtreme chilling with 655/D5?
I also have a Hydor L20, but I think that it is poor for the SLi, not? A MCP600 could do the job better than the D5/655? I have acces to a MCP600 too...
BTW, how about the VGA blocks, do they work OK with those temps??
Any sugestion about insulation, coolant to use (I think that antifreeze will freeze at those temps) or so??
Any sugestions or ideas are wellcomed... ;)
Thanks in advance.

[SexyMF]

I pulled down my 5:4 mix of antifreeze to -50C and it just was starting to form ice.

But thats besides the point because you will be hard pressed to get -35C with a single stage chiller. Go DD dual head for your SLI setup.

[Gautam]

-35C is possible with a beefy enough compressor np. Denatured alcohol is the coolant you're looking for. Sort of pricey, but won't freeze till -114C...now that you'd be hard pressed to get with a chiller. :p 1/4" neoprene everywhere should suffice.

No idea about the pumps whatsoever, sorry.

[Lord_RTKK]

Thanks for your replies... ;)
Well, my idea is not to use a comp to make the chiller... The idea is to use Dry Ice to cool the water of the loop, with a heat exchanger made of copper (I know that I cant mix dry ice with water... ;)) so the problem is that the temperature of the water could be -60 or -65 at the heat exchanger I think... :stick: :stick:
For this I am doubting about wich pump to use... because I dont know if all pumps can work with those temps...
The idea of the alcohol as coolant is good, but what type of alcohol?? Should etanol do the job?? I can buy cheap etanol, but I dont know how pure it is... (it is sold under the name "Alcohol de quemar", something like Alcohol for burning... xD)
If etanol doesnt works, any other ideas?
Greetings.
Lord.

EDIT:
I have been looking for diferent types of alcohol, and found that the typical alcohol that is sold at the chemist (the typical alcohol 96º) is etilic alcohol, so it freezes at -114ºC, is miscible with water and more fluid than water. Do you think that a mix of water/ethilic alcohol @ 1/4 will do the job??

[Lord_RTKK]

Well, anyone know anything about wich pump to use at this low temps?? :(
Also want to know if the mix between alcohol 96º and water, or only alcohol, should do the job...
Help me a little, please... ;)
Lord.

[madgravity34]

I know one user, plywood, did the same thing with his single x1800xt and the pump he used was this one:
http://www.dangerdenstore.com/product.php?productid=178&cat=23&page=1

Also, he used acetone in the loop.

EDIT

Here is the thread for your info: http://www.xtremesystems.org/forums/showthread.php?t=85550