Wanting to install a side panel CPU duct...

Well this forum is costing me a fortune on new PSU's, fans, cables etc, but I'm addicted!

Having successfully done my 1st case mod (cut and installed a 120mm fan pointing right at by 6800GT, I've now got the bug to carry on and add a side duct into my case directly over the CPU. Ideally I'd like to buy a pre-made duct rather than rely on my limited DIY skills.

In particular I've been looking at 120mm duct - matches my case colour and 80mm/92mm duct . Now, my CPU has an XP-90 with a 92mm Panaflow high fan, and my current temps are never above 32C when idle and 40C load.

1. What would you suggest I choose, the 80/92mm duct (with 78mm internal diameter) or 120mm duct (with 92mm internal diameter)? Don't want the duct to be too small then again a duct too big will not focus the full intake air into the CPU fan.

2. Should I use a mesh over the duct on the outside of the case? How much will this affect the airflow drawn into the case?

3. How far away from the CPU should the duct end be?

4. Would I be better off installing another side fan directly over the CPU and make my own duct to the CPU, out of cardboard/acrylic? Therefore creating greater airflow than the passive plastic ducts in the link? Also is it right that this new fan should have more CFM than the CPU fan?

5. Is it really worth all the hastle and expense or is it a bit unrealistic to expect any lower temps than I'm currently getting?


Sorry for so many questions, got a bit carried away there!! Thanks for your patience in reading this

1) Use the 120mm duct with a 120mm Fan...bigger is better. Make it a fast one and you can ditch the fan on top of the HS.

2)I dont like to use a filter or mesh over fans as it can reduce airflow as much as 25%! depending on the type.

3)If you remove the CPU fan try to have the duct covering half of the HS.
If you dont remove the fan on the HS then have it end about two inches above it.

4)Yes bringing the cool air and pressurising it above the heatsink is better tan passive cooling. Yes.

5)No. I think your temps are pretty good unless you want to push your CPU farther.

Thanks philippmike

How would I go about putting a fan inside one of those ducts though? Or would you recommend I just make my own duct.

Also, I have a spare Panaflo 92mm Low. I could put that on the XP-90 and put the High speen Panflo on the side of the case.

I also have a spare 92mm fan shell. How about I put a fan and spacer on the inside of the case therefore acting as a duct?

you don't have to have a tube, if the volume of air coming in through the side hole is more than what your HSF takes in.

you don't have to have a fan in the side hole, if
- the HSF is being used to suck in air thru the side hole (via a tube.)
- or, the case fans (being on exhaust) are being used to suck in air thru the side hole.

so it can be very simple.

I don't recommend ditching the heatsink fan if you install a duct. You have good temps already. A duct works well, but just a hole in the side panel with a fan mounted would certainly be better than nothing and you can always add a duct later if you want. Look at the link in my signature for how I did cooling mods to my cheapo case.

Actually have your link already bookmarked batboy. It's a great article.

Your side duct is exactly what I'm thinking of creating. I'd love to be able to buy that type of duct (that screws in and it extendable) but can't find one anywhere. Especially in the UK. Any idea where I can get one?

Just for the record, I have:

- 2 80mm (27 CFM) front intakes (but they are largely behing the hard drives and don't allow much air into the chassis.

- 2 80mm (27 CFM) rear exhausts

- 1 80mm (27 CFM) top exhaust

- 1 120mm (Panaflo High on a fan controller) at the base of my side panel focusing on the graphics card

Still concerned the CPU fan isn't getting enough fresh air though.

another rule of thumb is that two fans chain-ganged end up pushing air more like the weaker fan than like the stronger fan. So make chained fans about equal.

another rule of thumb is that ducts don't have to be airtight and in fact often seem to do better with some airgap. This is probably because fans hate back-pressure, and a sealed duct can easily induce a pressure differential.

another rule of thumb is that fans should generally be chained (by which I mean pushing the same air in the same tube) only if there is some obstruction or impedance between the fans.

addendum: and yes, keep a fan on your HS, because you want the fan right on your HS throwing fast strong vortices of turbulent air into it. Though the smoother flow from a distant fan or a reversed fan will still do some good, why not milk the energy the fan spends throwing out whirlpools of air... that's my theory anyhow.

also make sure your fan hole and cpu fan are right above each other