Alternator Shield

[Pato911]

I replaced the voltage regulator this weekend on my '87 Carrera and noted that the air duct/ deflector shield that is supposed to be on the back of the alternator was missing. It made the job a lot easier but is this a critical piece? Do I need to try to source a replacement? I called Mike @ Rennsport (he rebuilt the engine) and he said a lot are missing or broken and didn't consider it critical but I figured I would get the PP opinion as well.

Special order from our host (OEM-91110605501).

Thanks,

Patrick

[Bob Kontak]

They have fins on them if I remember correctly. Must be for a better distribution of blown air across the tops of the cylinders.

Far be it from me to butt heads with a pro, if you know what I am saying. For $100, you can put the issue to bed if you install it yourself.

[wwest]

I had the impression that it was less a shield than an airflow "guide" to help cool the alternator.

Maybe why your integrated VR failed....??

[Bob Kontak]

Originally Posted by wwest

I had the impression that it was less a shield than an airflow "guide" to help cool the alternator.

Here's some pics. It definitely has something to do with air flow.

That big hole where the wires enter has to be big for a reason. Interesting that air would have to enter as a diversion from primary air flow based on my guess with the arrows.

[wwest]

Venturi effect to "pull" cooling airflow through the alternator?

[Pato911]

Thanks for the photo; I didnt really know what it looked like from the parts catalog sketch. I cannot determine the orientation from the picture. Are the fins only on pne side or symetrical when installed?

Actually, I think the alternator gets more air without the shield. The front of the fan has no opening for air to get to the alternator, it all goes around the outside of the alt. The shield would block flow from even getting to the VR or side/ back of the alt. As for the big hole for the wires, no reason to make it smaller.

Perhaps it directs some flow to the rear most cylinders and maybe straightens the flow a bit (fin bend seems to be opposite the fan blades). Maybe it blocks water from the alternator connections when it is raining and the fan is pulling in a bunch of water/ mist.

[Pato911]

I like the venturi thought. Interesting.

[Len 911]

I noticed in the pic above a ground wire on the engine block to the fan housing. I took mine off the other day and I do not have this, Do I need to add one. I have an 85 3.2 do i nee the ground the housing?

[akkbhart]

I had the same question about 1 year ago, when 1 replaced the alternator. See the link below (or search for "shroud")

Alternator Cone/Shroud?

Btw -- all myn trusted mechanics and Porsche guys strongly suiggested that the shroud and fins are important for cooling the two front cylinders.)

[Pato911]

Thanks, I somehow missed your thread when I searched. I suspected the cylinder #1 cooling answer based on the photos... but #2 is farther forward than #4... whatever. Is the shroud metal? Regardless, I guess I will be ordering one tonight.

[Bob Kontak]

Fins are metal. Body plastic.

Fins are on the left side. Pretty sure there is one way only to install it.

[tirwin]

I happen to have mine out. Since I am cleaning up stuff I painted it with high temp paint. More pics.





I cleaned up the schmutz on top of the engine in the pic below so you can't see it but the way the air drafts through the vanes you can see a definite pattern to the airflow as there is a greater schmutz buildup in some areas.



$100 for that piece of metal and plastic seems awfully expensive.




Sent from a tiny screen

[pors1968]

Agree with BOB only one way to install it .Make sure to try it in hole before tight it.

[Bob Kontak]

Originally Posted by tirwin

$100 for that piece of metal and plastic seems awfully expensive.

I have the internal regulator on my 81 (external original). The original diverter is a cobbled up, JB Welded, bailing wire, dremel cut up contraption. I have found used ones that will fit properly over the V reg and they are close to $100.

Pretty sure the 87 is not the same one as what I need.

You gonna be using that one?

[timmy2]

Fins also direct air to the oil cooler iirc.

[Bob Kontak]

Originally Posted by timmy2

Fins also direct air to the oil cooler iirc.

There has to be some science to it. From the looks of things it forces air down on the left side. Oil cooler is the primary exit behind #6 so air would naturally move over that way anyways, the layman supposes.

Then one thinks, how does #4 get cooled as Pato911 mentions.

It's as if Germans designed this thing.

[tirwin]

You gonna be using that one?

Sorry, Bob... this one is accounted for.

[mysocal911]

"I had the impression that it was less a shield than an airflow "guide" to help cool the alternator."

"I suspected the cylinder #1 cooling answer based on the photos"

Both logical, as more than one purpose.

[SCadaddle]

Originally Posted by tirwin

$100 for that piece of metal and plastic seems awfully expensive.

Wait until that pretty cad plated yet rusty and crusty lower window channel falls off of your door window and regulator.....you'll think $100 for that part is a bargain!

[gamin]

Pato911 - If you don't have one of these you need to get one. It's there for a reason. Local engine builder wouldn't button up a motor without one. $100 is chump change in the Porsche world. Get one from a Porsche junk yard. Be aware that there are different versions so be sure to get the Carrera one. They are fun to install. Hope you have small hands. Don't over tighten the fasteners. The plastic will be old and brittle.
Len 911 - Yes, you need the ground wire.