PS3 Can someone explain different performance with radial fan configuration

[Abomination]

[edit] this concerns a PS3 slim.

As I mentioned in another thread, I replaced the original ps3 fan with a pc-case-fan.
I made a test-case (ha!) by replacing the top cover with a cardboard one, so I can test different places to place the fan.
I blocked all the ventilation holes (except those in the back) so any moving air would have to pass through the heat sink.
This ps3 has no bluray so I thought that that position would be ideal to make a hole for the fan.
Another configuration is to mount the fan directly in the space of the original fan and have a hole in the cover above it. Fits like a glove..
I thought that the position over the (ex)-bluray would work better, because the air could flow more freely, as opposed to the (ex-)ps3 position, where the air would 'bounce' on the bottom and interfere more with the(aerodynamic) working of the fan .
But my testing seem to prove the opposite. More air is exhausted out the back in the latter case.
Anyone care to guess why this could be? (I hope I explained the situation clear enough)
Also: any suggestions to improve the performance of this idea are welcome.
T.I.A.

p.s. as a point of interest:
The radial fan (in the original position) cools, with 50% speed, as good as a ps3 fan with 25% speed.
But it is more silent.
I have not tested higher speeds yet.

 

[flowlapache]

Hey! I can't help you but I would like to know...
And see with pictures what you did! thanks

 

[Abomination]

Both PS3s have broken blue-rays. I wanted to see if I could use that space to house a fan, since both original fans were defect. (Probably not a useful solution)
I can't show all that I did, because much was done with cardboard and masking tape.
Being repurposed and/or binned.
I used webman's manual speed settings of 20%, 50% and 60%.
All testing was done with a 90 cm fan and a 120 cm fan. The results were similar. Except the bigger fan was more silent.
I tested with the fans pushing as well as pulling in every setup.
Blowing air in was always more cooling than sucking it out.

(a little adapter cable. black is fan connector [gnd, 12v, pwm]. white is [12v and gnd.])
In reverse order of effectiveness:
1. A fan in a hole over the blue-ray area.
2. A fan in a hole over the blue-ray area, with all ventilation holes closed, except the exhaust grid at the back.
3. A fan in a box in the blue-ray area, connected via a hole in the side of the (original) fan bay.
I'm guessing that it does not work as good as option 4, because there is a bigger volume to create pressure for, and the box just adds turbulence. The problem of back-draft (the air hitting the bottom) stays the same.

(rescued from the bin) (Imagine a fan in the cutout)
4. Placing a fan directly in/on the fan bay.

(cut open fan bay to adjust to bigger sized fan. on the right side the previous connection with the cardboard box...)

(Temporally mounted with the assist of bbf masking tape)

(Underside of smaller fan. Corners were cut and rounded to fit in the bay. The black surrounding is cut out of an old mouse mat to create an airtight sealing)

(This is how it fits. The holes for the screws correspond with those for the fan )
My findings. (for what it's worth):

A radial fan can not be as effective as the original centrifugal fan. A redial fan can only suck or blow, whilst the PS3 fan pushes the air through the heat sink as well as sucks air from over the motherboard and also from under the heat sink. (Closing any of the holes in the bottom of the fan bay has an unproductive effect.)

My final setup (the smaller fan IN the fan bay)seems to be the most usable.

It does need a hole in the upper side of the case though. Whether it needs an airtight binding with that hole needs to be seen.
That's it!
cheers

 

[flowlapache]

Super great!! Nice done, thanks for explanations and pictures!!