CPU cooling mod - Ducting air with 82mm flex hose

Air duct

  Remember the goggles where appropriate:

Safety goggles

This page is a step-by-step guide on how to make a cheap but effective flex hose air duct.
Normally, a CPU cooler just cycles warm air from inside the case though the CPU cooler's fins. A CPU air duct draws cooler air from outside the case directly onto the CPU cooler, making it more efficient.

Tools needed:
  • Hobby knife
  • Metal file
  • Metal saw
  • Hot glue gun
  • wire-cutting pliers
  • Screw drivers
Hardware needed:
  • About 60cm of standard 82mm ventilation flex hose (available at most DIY centers)
  • Old 80mm fan (doesn't matter if it's defective, it's going to be cut in pieces anyway)
  • Double-sided tape (the kind made for holding carpets in place)
  • Long zip ties
  • Self-tapping screws and/or 4mm machine screws and nuts
First the result:

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Air duct with passive front intake. With this setup, my old Athlon XP 1700+ (Thoroughbred "A", mildly overclocked to 1600MHz) runs at 40 degrees Celsius under full load. System temperature: 28 degrees Celsius. The CPU fan is a 80mm 2050RPM Papst unit.

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Find an old worn-out 80mm fan.

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Cut out the center piece.

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Attach it to a piece of wood or similar so it's easier to hold on to.

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Sawing time. You should place the cut so the result will be a cylindrical end. Some fans will have a better shape than others.

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The result. Keep the cut-off flange, it's a great 80mm fan template when you mark holes to drill in your case.

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Trim down the corners of the remaining piece.

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...And the inside fan motor attachment points too.

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Fill the wire cutout with hot glue and trim it down with a hobby knife after it has cooled down. This will make the fit towards the CPU cooler fan as airtight as possible.

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Now for the tricky part. We need to make sure the flex hose stays on.

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Cut a narrow piece of double sided tape..

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Wrap it around. keep the extra layer on for now. Trim off the overlap, but only the sticky part.

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Now fold the overlap like that.

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Put the hose on the flange. Now while holding it on, carefully pull the strip out all the way round.

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It is now attached. To make sure it stays that way, put a long zip-tie around.

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It should look like this. Now measure the the length needed for the hose and repeat the steps for the other end.

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Attach one end to an existing fan mount position in the case and the other to your 80mm CPU fan with either long screws all the way through (shown to the left) or with two short screws (shown to the right). Be careful to not crush/chip the core of your CPU while mounting the duct. It might be a good idea to detach the heatsink from the CPU while working on it.

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The finished result again.