60mm vs. 80mm

[Jeff Bolton]

I've been thinking about getting a new heatsink to replace the stock Coolermaster that came with my tbird. i already have the 38cfm delta screamer which helps me achieve a modest overclock and keeps temps pretty darn good.
i was thinking of upgrading to the thermalright sk6 heatsink, very good from all i've heard. but today a lightbulb went off.
if i got an alpha pal 8045 heatsink that accomodates an 80mm fan, and an 80mm fan with a similar cfm rating as the delta, would i be able to get the same cooling effects? the delta pushes 38 cfm and is 46 decibles. i can get an 80mm Sunon that's 50cfm and only 40 decibles.
so i guess my question is, with the larger heatsink and fan, would i get better cooling effects? equal to what i have now? worse? i'm wondering. because the noise from the delta isn't too much to handle, but i figure cutting it down 6 decibles couldn't hurt...but do the extra 12 cfm actually make a difference after you make the transition from 60mm to 80mm? i want to keep at LEAST as good cooling as i have now.

thanks,

jeff

[klosters64a]

If we assume that the actual size of the HS remains the same(changing from a standard "60mm" HS to a extra large HS like the PAL-8045 throws a variable into the equation) this is how the diff between a Delta 38 60mm and a 80mm fan on an adapter looks: The 80mm fan needs to push 68cfm to equal the Delta 38's efficiency. This surprised me.

A lot of cooling power is lost with a 50 cfm 80mm.

[Jeff Bolton]

that's what i needed to know. i'll stick with the screamer and update the heastink with some AS2

thanks

jeff

[Sonny]

Originally posted by klosters64a
If we assume that the actual size of the HS remains the same(changing from a standard "60mm" HS to a extra large HS like the PAL-8045 throws a variable into the equation) this is how the diff between a Delta 38 60mm and a 80mm fan on an adapter looks: The 80mm fan needs to push 68cfm to equal the Delta 38's efficiency. This surprised me.

A lot of cooling power is lost with a 50 cfm 80mm. Yup since adaptors were designed with no regard for proper airflow, seems like the only requirement of the design was to get a 80mm fan fit onto a 60mm HS. Velocity Stacks are a differeent story.

jeff - If you can afford to purchase an Alpha Pal 8045 then do so. It'll beat any 60mm fan based HS on the market even with just the 50CFM Sunon. I do have one suggestion for you; use a 80mm 80CFM Delta EHE with it on a rheostat. That way you can slow it down to keep your ears happy. The thicker EHE would give you better flow compaired to the SHE just because of the blade design.

[donny_paycheck]

I think as far as air cooling goes the 8045 is the best dollar value out there and the second best in performance overall, bested only by the MCX462 from Swiftech. For $30 less than the MCX462, I'd go with the 8045. I have an 8045 on the 1400/266 tbird in my sig and a MCX462 on the peltier setup there and both of 'em work awesome. I used the same Sunon fan you're talking about with the 8045 and it's quieter and cooler running than ANY 60mm heat sink/fan setup you can find - GUARANTEED. To sound redundant I'll also say nix your idea of an 80-60 adapter as it provides so much back pressure on the fan that the fan needs all the extra capacity just to force enough air through to make a difference. The big HSs have MUCH more thermal mass and area than the small ones so they absorb and dissipate more heat plus they don't generate as much back pressure. Sonny's got a good point about using a rheostat to vary the speed of a fan. The SHE and EHE series fans from Delta Electronics have stator vanes built into the housing and steeper blade pitches so they generate less turbulent and higher pressure airflow.