911 Cooling Shrouds - Improving Internal Air Distribution

[Bad bug]

Thank's alot wally that's the 911 fan that i have but one of my deflectors is missing.

[Sandeep]

Thanks for the comments Jake.

I reprogrammed my logger to flash an LED when the hottest temp from any cylinder reaches 375F. On a full acceleration run from a dead stop, gas pedal to the floor in each gear, 5500 rpm shift, #4 hits 375F at 4th gear, 3800 rpm consistently.


Thanks for the pics Wally.

In the diverter picture, it looks like you may only be getting 3/4 of the airflow from that quadrant as it looks like some air may getting past that last diverter to the left in the pic, if you compare it to the alternator guide diverter. I know you are using the 964 setup now though.

My idea is to use 3 diverters, one each directly behind the stock alternator ring diverters and one in between to make 2 channels to capture all of the airflow of that quadrant of the alternator ring. This will mean changing the positions of the factory alternator cap diverters.

The factory alternator ring diverters look to be of an airfoil design and I will try to incorporate the airfoil shape into my diverters placed on the alternator cap. I will keep placing diverters around the alternator cap, taking more air from each neighboring quadrant on the alternator ring until I can equalize the temps. That is the plan anyways ! Who knows if it will work until you try it.

Sandeep

[Wally]

Originally Posted by Sandeep

I will keep placing diverters around the alternator cap, taking more air from each neighboring quadrant on the alternator ring until I can equalize the temps.
Sandeep

Yes, that should be 'relatively' easy to do. However....it may result in that you take air away from your cooler running 1/2 side to a level where both sides run equel temps, but generally too high!
I think you need to direct the air also to flow from top to bottom over the heads. That is the direction of the fins after all!
To accomplish this, I think I also need more room in my shroud, at least more above the heads. My simple 'steel plates' over the cylinders won't cut it, but it is a start in that direction. I also think that dumping the air from above is the key succes element of the type 1 cooling way: its in the direction of the fin area (duh..!)
The more advanced shrouds (which I consider the Klaus, Remmele and RMB ones, maybe even Gerd Weiser's shroud) do seem to have more room above the heads in the shroud and even more above the 2 and 4 cylinder than over the 1 and 3 cylinder. Not by chance I think. Those shrouds are also 'flatter' right behind the fan. Probably to even out the left/right side flow better. Ever noticed that?

In the end, you very likely to end up redevelop/design your own shroud. Jake is probably right about that

Regards,
Walter

[Sandeep]

Great points Wally. By equalizing the temps in the way I mentioned, you are right ... they won't nessesarily be cooler (hotter I would think) but they may be even

The airflow must be directed from top to bottom as you have mentioned. Check out Remmele's website under his pictures section and look at the pic of the inside of his shroud ... it is quite flat right behind the fan and it looks like this dumps the air vertically between the cylinders.

I'm sure this shroud uses the 964 setup and with the vanes you have shown on the 964 fan, you are much further ahead than I, I would think, down the road to improving cooling.

Perhaps a 964 fan setup is in my future ?

Sandeep

[Wally]

Originally Posted by Sandeep

I'm sure this shroud uses the 964 setup...

Sandeep

Thanks Sandeep
The 'new' curved fan blade houses and fans/generator combo's you can buy at bug stores 'everywhere' do NOT use the housing of the original 964!! So, AFAIK, you still get the old 4-vane style fan housing. That fan housing is a new mould, where a Valeo generator fits in nicely. Also, the original 12-blade fan is turned down to a 225 size if I am not mistaken. Anyway, a considerally amount of original fan blade is removed from the tips. I don't know how that effects cooling air.
Probably 'they' thought that the amount of air was more than enough, maybe even to much (as Jake also has said sometimes), so it would be no problem. I don't know...Most 'old-style' german tuners still prefer the old 11-blade I heard once...
So don't be put down by the 11-blade: its damn good; it just needs to learn to behave in the presence of our type 4's

Regards,
Walter

[Bad bug]

I feel left out. I don't have any data to share but i do think if done right the 11 blade will work. Samcat had a 11 blade setup that di work well on a stock 2.0l type4.

[Sandeep]

I have finally received my 11 blade fan factory diverter in the mail ... time to start playing and logging the data

Its a good thing the 911 fan/alternator setup can be removed from the shroud and unwired in about 3 minutes :agree:

Sandeep