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-   -   Side 80mm Fan In vs. Out (https://www.hardwarecanucks.com/forum/air-cooling/21814-side-80mm-fan-vs-out.html)

Dadi_oh August 11, 2009 03:15 PM

Side 80mm Fan In vs. Out
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I have a smaller case, an Ultra Gladiator with a 120mm inlet fan and a 120mm exhaust fan. The power supply has a 135mm temp controlled exhaust fan. I also have a pair of 4870 video cards with the original heatsinks (exhaust outside of the case) running at 40% fan speed.

The case also has a side port but due to the height of my OCZ Vendetta 2 heatsink I can not put a fan on it so it is just a grill. However, there is a side vent down near the video cards so I decided to throw a 80mm fan on there.

Here is where it gets interesting. I was thinking about whether to run this fan as an inlet or an exhaust. So I ran some experiments and was rather surprised by the results.

It is fairly warm in the room, about 26-28C. I am using speedfan to measure my system temp (I assume the motherboard temp somewhere on my P5Q-PRO) and the core temps.

First I ran the system with the side 80mm fan on exhaust with Prime 95 small FFT's to warm things up and measured a system temp of 44C.

I then ran 3DMark06 looping through all the tests to get the video cards warm and measured 50C system temp.

I switched the side 80mm fan over to inlet and ran the same experiments and got just 36C with Prime95 and 43C with 3Dmark06 looping.

So to summarize:

Test 80mm exhaust 80mm inlet
P95 small FFT 44C 36C
3DMark06 loop 50C 43C

My theory is that is I put the 80mm on exhaust I end up with exhaust fans of 120mm (rear) + 135mm (power) + 80mm (side) vs. only a 120mm inlet (front). I think this sets up a negative pressure in the case and the exhaust feature of the 4870's can't work properly against that pressure.

If I switch it to inlet then I have a 120mm (back) + 135mm (power) vs. 120mm (front) + 80mm (side).

Just a piece of info for anyone in similar circumstances.

Sushi Warrior August 11, 2009 03:27 PM

I have the same case and found the same thing. The front HDD bays basically make the front 120mm useless....

mo' power August 11, 2009 05:55 PM

I would use it as an intake to provide a bit more fresh air circulation for your video cards.

Dadi_oh August 11, 2009 06:53 PM


Originally Posted by mo' power (Post 238787)
I would use it as an intake to provide a bit more fresh air circulation for your video cards.

Yup. That is the way this setup works best. Video cards are hitting about 60C on the cores during gaming which is pretty reasonable.

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