Fan upgrades - let's un-complicate this once & for all!

[Porsche-O-Phile]

My fan (impeller) has a small chip out of one of the teeth of the blades. It is an 11-blade model, part # is 901.105.101.5R. I assume this means at some point in the car's history it was "upgraded", since I believe the 2.7L engines came originally with the 5-bladed fans that partially contributed to the overheating-related issues with the magnesium cases.

Anyway, the chip in question is small, but I still want to replace the fan at some point with a new or "nearly new" one. I'm wondering what the "best" fan that will provide the most cooling flow on a 2.7L engine is.

It seems to me this would be the 11-blade fan with the smallest-diameter pulley, which would result in the fastest fan rotational speed per crankshaft revolution. There are three choices that show up in the Pelican catalog - here's the page:

http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_ENGmis_pg2.htm#item9

The fan with the smallest diameter pulley is P/N 930-106-011-01-OEM, and is naturally "NLA". So that one's out. The next-best one appears to be the one with the 3.25" diameter pulley, P/N 930-106-012-00-M100.

There is also another 11-bladed fan with a 3.75" diameter pulley (wouldn't rotate as quickly and consequently wouldn't cool as well - at least one would think. . .), P/N 901-106-010-03-M100.

I find it odd that the fan with the larger diameter pulley is almost twice as expensive as the "better" fan, but there you have it.

So it appears that the best fan upgrade would be the 3.25" diameter pulley one, assuming I can't source a 3.125" diameter one someplace. Is this correct?

Next question: Can't I simply retrofit 3.125" (82mm) pulleys such as the Roethsport ones or others available here onto the 3.25" pulley fan, effectively converting it into a 3.125" diameter pulley fan?



Now, onto the engine pulley. . .

The engine pulley (the one on the crankshaft) should ideally be as large as possible to give the maximum rotational diameter to the fan for each turn of the crankshaft, no? Is there a way to do this? Are there different crank pulleys? I do not see these in the catalog. Anyone know what options there are?

I was also told that there was a 130mm (5.118") diameter engine pulley that was used on some 911s. Coupled with a 3.125" diameter fan pulley (80mm), this would give a fan-to-cranshaft speed ratio of 13:8, which seems pretty good to me.

It should be pretty simple - just a matter of mixing & matching the desired parts, right?

[RoninLB]

only what I did on my stock Calif 5 blade


I used stock fan housing, crank pully and stock high speed 1/2 pully on a 245 11 blade fan.

P E T [top secret written] says my pully 1/2 is pn 90160342101

I punched it into pelican and is available for $20


absolutely no belt problems with the higher speed fan at red line +, and over 75k miles

I also use the 9.5 fan belt, not the 10 width

[spuggy]

I believe the 930 fan setup provides the best airflow.

Bill V posted numbers and ratios in this thread:

Difference in Pulleys from Carrera 3.2 to 3.0 SC

And in this thread, Will Ferch found the notes - including pulley sizes - he didn't have with him for the thread above:

5 Blade fan vs. 11 Blade Fan