What heat sink to use on Neu?

[suicideneil]

I would generally agree, but I guess it depends how extreme the setup is- thermal grease should solve any heat transfer issues though I would have thought.

[Finnster]

Originally Posted by suicideneil

I would generally agree, but I guess it depends how extreme the setup is- thermal grease should solve any heat transfer issues though I would have thought.

Thermal grease is really only very effective if its applied very very thinly and used to smooth out any minor defects. It really can't be used to fill in large gaps. By large I mean 0.1mm. I mean I guess its better than air being there, but it won't make a crappy HS work great if its poorly machined.

IDK if you've ever played around with building computers and attaching HS's onto CPUs. Things are easier today, but the HS for CPUs use a huge amount of spring force, like 30lbs+ to attach a HS onto the little die. Some extreme overclockers or terribly anal people would go further than even the huge aftermarket HSs and "lap" or sand down to a mirror-like finish w/ 1000 grit paper, then use Artic silver to fill in imperfections.
This is a bit of an extreme example as you are trying to dissipate 10's of watts out of a 1 sq cm die, but you could also easily see the results of your HS attachment skills. If you slathered AS all over the die, temperatures would be quite a bit higher. The thinnest scraping produced the best results.

Motor HS don't have to be nearly so efficient as that, and they have a much greater area to dissapate heat, but they do not attach to the surface w/ any amt of spring force, nor are the HS or motor surfaced generally well prepped for HS's and thermal transfer by contact. The machining is fairly rough. If you get some poorly machined cheap chinese HS, I wouldn't count on it doing a whole hell of a lot, and may actually be counter productive (trap air pockets.)

A 2.5D on 5S will be solid and lots of power for the track. More than anything its going to come down to driving skill and proper gearing to being with. With too much power its easy to drive out of control and just bounce off the walls as you watch the slow and steady guy just lap you. If you are getting anywhere near 160 or so, I would look at gearing and setup before fooling with HSs or fans or anything.