5 blade vs 11 blade 911 fan

[kdanie]

My 911 kit came with a 1.6-1 crank pulley, I bought a smaller pulley from Fat Performacne that is 1-1.
ken

[Alex]

For your info:

Latest dyno test showed that the fan took 6hp on Zen's engine.
If you get a pulley with a 1:1 ratio the Porsche shroud will NOT work that well.

Please wait a week or two.....I have some really good infos for my article.

Alex

[Tony Z]

Just picked up 11 blade fan kit, all for $320. Not bad hey?? Dry sump here we come, just gotta get the cash to finish the 2332 and it can all be installed

[Oliver Knuf]

For sure you have to interchange pulley-diameters, just to get the correct ratio.

A safe thing, to be warned, that the diameter is too small is, if the generator light comes on! LOL


5 blades for president! 12 blades are good, but...! 11 blades provide best airflow, besides it's less noisy than the 5 blades! Problematic is, that you can't get the 11 blades new.

[fast70]

So there is no real problem running a 5-blade fan? I am having a hard time locating an 11-blade fan. Would it cause any problems or should I keep looking for an 11-blade?

Thanks,
fast70

[Tony Z]

Think about it this way, the 5, 11 or 12 blade was designed to cool a lot more power, cylinders, boost and heat than we will ever need.

The only problem with running a 5 blade fan that I can think of is as follows.

I dont like the look. Yes, if nothing else was available, I would run a 5 blade (almost did too), in all honesty, I REALLY REALLY REALLY REALLY like the 12 blade, but those cant be found in SA, so I opted with the 11 blade.

It all boils down to looks!!! They each have their specific design application, which is much more than we need anyway.

[fast70]

Yeah,
I don't know what I was thinking! As if the fan for a 6-cyl would'nt be good enough for a 4-cyl. Thanks for showing me the logic!

Thanks,
fast70

[Split50]

The 5 blade fan was introduced to the 2.7 911 in the mid 70's to make the engine run hotter in order to reduce exhaust emissions.
How do I know? I have a mid 70's 911 and every thing I have read about it tells me to upgrade to the 11 blade fan before the engine overheats and pulls the head studs out of the case.
So the 5 blade fan cools less.
To confuse things even more there were 2 sizes of pulley too.

Tim

[fast70]

Yeah,

I think I read that in a Porsche manual once. They did it in order to reduce emissions by making it run hotter.

fast70