Adding 2nd 480, Best Way to Mod Loop ?

[rolodomo]

Adding a second GTX 480 (SLI) to my water loop.

Current loop is: MCP355 --> CPU (i7 920 at 4.2) --> NB --> GTX 480 (EK block) --> MCR 320 (Rad) --> XSPC Restop.

I really don't want to do a lot of re-tubing or spend $$. I'm thinking about just stacking a second MCR 320 (rad) to my first in a serial connection with 4-6 fans. The rads will be externally mounted oustside the case.

I realize flow rate will go down, but with two MCR 320(s) and plenty of fans, I should still get decent cooling.

Is this a good approach? Is there a better mod that doesn't involve separate loops or a new pump?

 

[aigomorla]

its possible... u wont be too happy with it on the cpu end tho, because u have a higher base at idle heat.

2 x 480's are no joke when it comes to heat output.

 

[rolodomo]

its possible... u wont be too happy with it on the cpu end tho, because u have a higher base at idle heat.

2 x 480's are no joke when it comes to heat output.

Thanks for replying. I was in checkout line at microcenter with a 320 in hand when I read your opinion. Makes me buy a bit easier, but I realize I'm scrimping a bit and idle temps will go up. I'll add a new pump (new loop) if this doesn't work.

The second 480 is an evga 480 hydrocopper ftw (fleabay $300). Not a full cover block, but the price is right. Hope the gpu is a golden bin. At the price evga charged new, it should be!

 

[aigomorla]

Thanks for replying. I was in checkout line at microcenter with a 320 in hand when I read your opinion. Makes me buy a bit easier, but I realize I'm scrimping a bit and idle temps will go up. I'll add a new pump (new loop) if this doesn't work.

The second 480 is an evga 480 hydrocopper ftw (fleabay $300). Not a full cover block, but the price is right. Hope the gpu is a golden bin. At the price evga charged new, it should be!

its not about the radiator...

your not looking at the entire system.

Flow is proportional to the amount of heat which water can pick up.

The average flow in a system is roughly .75-1gpm.

That means u can roughly have 300-350W on your connection line, and only have a 1C increase in overall water temp once it passes the heat source.

The problem is, its very difficult to get more then 1gpm efficiently.
As you go higher in flow, the radiators become less efficient, and the blocks as well.

So when planning out a loop, you always look at how much flow you have in net relationship to the radiator which can disperse the heat.


Example incase im not making sense..

1. you have a pickup truck which can only pick up 1ton of trash. (water flow)
2. you have a trash pickup site which is constantly dumping 1ton of trash. (heat source)

In this relationship its perfect... its efficient.

Now another scenario

1. Your pickup truck can only pickup 1 ton of trash.
2. Your trash site is dumping @ 1.5 ton of trash.

That means u have an excess of .5 tons, which will translate into a higher delta T. or the temp difference between ambients and watercoolant temp.

 

[rolodomo]

Thanks for the info. I'm hoping my 355 pump can push the water through both radiators (series) at .75-1 gpm.

Here's the new loop: 355 --> CPU --> NB --> GPU --> GPU --> 320 --> 320 --> Restop.

Almost wish I had a 655 pump (and a flow meter) now, so I could experiment with different pump settings.

 

[mindwreck]

it won't be terrible. but expect to use not-so-quiet fans.

how are your temperatures now?

 

[rolodomo]

it won't be terrible. but expect to use not-so-quiet fans.

how are your temperatures now?

My CPU temperatures were normal for a watercooling setup at 4.2 GHz, topping out at 75 C or so during overclock testing (e.g., prime). After the water warmed up, it would idle a few degrees above ambient. My first 480 GPU did very well, approx. 55 C under a game load (never tested furmark).

Yes, I'm going to need high rpm fans, no way around it. I wonder what's a good high rpm fan to use mounted against a radiator to minimize noise? I know the s-flex is not considered the best Scythe to get, but I've also read its straight, blade design does well mounted against the fins of a radiator, noise-wise.

 

[aigomorla]

scyth GT's are the best fans for rad if you like your hearing not impaired ...

And the reason why i gave u that long lecture was to tell you, with that much heat inside your loop, you will form a temp gradiant.

So your inlet and outlet of your rad can vary by as much as 2C while a normal system it wouldnt break 1C.

 

[rolodomo]

Thanks everyone for the feedback. Here's an update.

Performed the SLI mod. Pretty good temps (one monitor connected). Max temp 48 C and max power consumption 510 Watts running Unigine 1080p default except 8 AF, 4 AA.

I have two MCR 320(s) stacked with some space in-between that is closed off by a shroud. I running four fans right now. Haven't installed the Scythe GT(s) yet (on order).

It almost seems like my temps are better now. Strange, perhaps I fixed a problem with the existing water loop when I performed the mod.

Idle power consumption (e.g., browsing) is 195 W, better than I thought it would be!

EDIT: Forgot to mention, i7 920 was set to default for tests. I usually run at 4.2 at 1.4V, which would add another 150 W approx. (under full load) to max power.