Side panel fan question/ezperiment

[EvilSponge]

Hello all,

I am using a Antec900 and I have a question about fans and CFM. I recently replaced my thermalright 120 ultra extreme cooler with a Zerothem NV 120 as the thermal right would not allow me to run a side panel fan which really helps with temps in my experience. In any case I have my Q6600 running idle at 35-36c with speed step enabled. and 66-67c prime95 full load 6 hours. I experimented with three 120mm side panel fans.

1) Thermaltake 120mm fan 78CFM Loaded temp 68-69c fully loaded 2 hours prime95

2) Thermaltake silentcat 120mm fan @ 67CFM Loaded temp 68c fully loaded 2 hours prime95

3) Scyth Flex 120mm fan @ 42CFM Loaded temp 65-66c fully loaded 2 hours prime95

All temps monitored with latest core temp program

Now I thought a higher CFM fan would lower temps not raise them?
Why is the lower CFM fan cooling the best?

If anyone has an answer I'd like to hear it.

Thanks,
-sponge
BTW the Zerotherm with side fan is 2 degrees cooler than my thermal right without sidefan

 

[imported_Scoop]

You could have tried without the side panel fan and see if the temps would drop even lower 😛

 

[Zepper]

A side fan better helps downdraft HSFs. A front to rear flow HSF can have its air starved on the intake side and/or blocked on the exhaust side by an airflow down from the top. One just has to think about the competing airflows to see that. If you create an airguide to aim the air from the side toward the intake side but some away from the HSF, you will get better results. Morals: If CPU cooling is the aim, make sure all air sources work synergetically with the CPU fan's natural airflow pattern - and extra fans can actually make things worse rather than better. The lower CFM fan has less air velocity so it has less effect on the HSF.

.bh.

 

[EvilSponge]

Thanks Zepper ok that makes sense so the higher cfm fan can be disrupting air flow. Yeah forgot to add I did the experiment without side fan and my temps were 69-70c this is why I moved to the new cooler to fit my side fan. Now all my case fans are set to medium for noise considerations I'll do another experiment with them on high

-sponge

 

[Bluefront]

My guess would be that the Thermaltake fans are not pushing as much air as the specs would have you believe, particularly when blowing into a resistance. Companies like Thermaltake and SilenX, are guilty of much exaggeration in this area.

 

[Jessica69]

Originally posted by: Bluefront
My guess would be that the Thermaltake fans are not pushing as much air as the specs would have you believe, particularly when blowing into a resistance. Companies like Thermaltake and SilenX, are guilty of much exaggeration in this area.

Damn....I think you are being too kind and gentle on the SilenX fans. 😉

Some independent testing on two of the SilenX 120mm fans, the 18dBA/90CFM and the 14dBA/74CFM fans, showed their open air performance was more like 37dBA/60CFM and 38dBA/56CFM respectively.

To me, SilenX's "ratings" on their fans are outright fabrications and pure lies, to say the least.

 

[Bluefront]

Just trying to be diplomatic.....but as you say, SilenX specs=pure lies. :|

 

[NicColt]

Originally posted by: EvilSponge
Now I thought a higher CFM fan would lower temps not raise them?
Why is the lower CFM fan cooling the best?
If anyone has an answer I'd like to hear it.

That's because I'm willing to bet that your blowing air in, turn that fan around and have it suck air out and your temps may drop 1 or 2 degrees.

By blowing air in from the side your basically blowing hot air from your vid cards onto the cpu, let the front intakes blow air in and let the two back fans and side fan take air out.

I have a 900 incoming right now, and I've done that experiment several time in the past week on my TX1050b and my temps did drop by having the side fan sucking air out.

 

[EvilSponge]

Thanks NicColt I'll try changing it.

-sponge