Bill Gregory

There was some discussion recently about the Patrick Motorsport Hub adaptor ($89), versus Performance Products ($179). Since I just got the Porsche RS hub from Gert, thought I'd post some pictures. It's part number 993.106.051.80, and applies to 993's and 964's. Price from Gert is $80 plus shipping. This part allows you to convert to one fan belt for the fan and alternator, as the RS's did.

Bill Verburg

What else is required for the switch?

Bill Gregory

[quote]<strong>What else is required for the switch?</strong><hr></blockquote>
Bill,

Nada. If you look at your existing fan and hub, you can see how the RS studs line up the same on the fan, and the hub fits on the alternator shaft. You eliminate the alternator fan belt and alternator shaft pulley (pulley on the crank stays), and reuse the existing nut and spacer off the end of the alternator shaft to tighten everything down. If I can finish mine up tomorrow, I'll post a picture of the finished installation.

Cupcar

Bill didn't mention that you can do away with the sensor for the fan belt (and it's light in the dash if you really want to save weight ). Since the fan and alternator are driven together, the alternator light serves the purpose of monitoring the single belt. <img src="graemlins/yltype.gif" border="0" alt="[typing]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Bill Verburg

No change at the crankshaft? The 964 has the pulley on the balancer, the 993 just has a pulley. I am considering this mod for my 993 but am curious about the 964 also.

Cupcar

Nope, pulley and/or balancer is the same in 964 and 993 RS as standard car.

Bill Verburg

I see 2 different 964 crankpulleys

• 964 102 050 01 which uses am M14x44mm bolt for M64/01/02/03 RS
• 964 102 050 20 which uses an M14x40mm bolt for M64/50 964T

Same pulley for all 964s I assume a triple groove for all?

and 3 different 993 crank pulleys

• 993 102 050 01 for M64/21-24 & 05-07 96-98 Carrera uses an M14x33 bolt
• 993 102 050 40 for an M64/20 99 3.8 Carrera RS using the same M14x33 bolt
• 993 102 050 41 for M64/20 w/AC uses the same M14x33 bolt

single ? double w/ AC? or double w/ triple groove for AC?

I thought I understood that the 964 pulley included an external balancer while the 993 does not? am I wrong in this thought?

Mike J

I thought one of the reasons there are two pulleys is to allow the alternator to run at a different speed than the fan. An I missing something or is this a mod for a "daily runner"?

Cheers,

Mike

Bill Gregory

[quote]<strong>I thought one of the reasons there are two pulleys is to allow the alternator to run at a different speed than the fan. </strong><hr></blockquote>
Mike,

That's correct. In stock configuration the fan runs a bit slower than the alternator. Installing the RS hub will cause the alternator to run at the fan speed.

Sputnik

Can I ask what is the main reason to change the factory installation to this -RS one? Any performance gain?

Bill Gregory

[quote]<strong>I see 2 different 964 crankpulleys

• 964 102 050 01 which uses am M14x44mm bolt for M64/01/02/03 RS
• 964 102 050 20 which uses an M14x40mm bolt for M64/50 964T

Same pulley for all 964s I assume a triple groove for all?</strong><hr></blockquote>The '01' part is for C2/C4, Tip, and RS, all use the same 3 belt crank pulley. '20' is for the Turbo, which has a different belt arrangement.

[quote]<strong>I thought I understood that the 964 pulley included an external balancer while the 993 does not? am I wrong in this thought?</strong><hr></blockquote>Yes, you're correct that the 993 does not have the external balancer the 964 has.

Bill Verburg

So the thought is for a 993 use 993.106.051.80, on the alternator, 993 102 050 40 on the crank. What pully on the alternator adaptor? What belt?

For a 964 use 993.106.051.80, on the alternator, 964 102 050 01(stock) on the crank. What pulley on the alternator adaptor? What belt?

Cupcar

Bill V'Berg, you are so right, the 3.8 RS engine does use 2 pulleys that are different than the 3.6 liter engine. One is for A/C and the other for no A/C, I assume there is an extra sheeve for the A/C belt.

The 964 normally aspirated engines all use the same pulley but the Turbo 3.3 and 3.6 each use a different pulley. My car has a factory RS engine with the single belt drive and there are 2 unused sheeves for the alternator and A/C.

All the normally aspirated 993 and 964 engines use the same fan drive belt so the diameters are probably the same for the pulleys across this engine family.

The 993 does not have the harmonic balancer that the 964 has since the reciprocating assembly is lighter and the crankshaft is stiffer.

The advantage to the single drive system as I see it is that the alternator is driven at a slower speed which saves a very small amount of horsepower and also this has a "light flywheel" effect since the alternator isn't being spun up to as high a speed and its inertial load on the engine is less. It is also a simpler lighter system.

The disadvantage though is that a slower alternator drive speed is less effective at charging the battery. Keeping the battery at charge during a given duty cycle depends on the way the car is driven and how much electrical equipment is on board. Short trips with the big stereo, A/C, lights on etc. may lead to a low charge situation. <img src="graemlins/yltype.gif" border="0" alt="[typing]" />

AES

I am also interested in knowing what pulleys top and bottom to use on a 97 v-ram. Any more info?

Bill Gregory

[quote]<strong>So the thought is for a 993 use 993.106.051.80, on the alternator, 993 102 050 40 on the crank. What pully on the alternator adaptor? What belt?

For a 964 use 993.106.051.80, on the alternator, 964 102 050 01(stock) on the crank. What pulley on the alternator adaptor? What belt?</strong><hr></blockquote>

Bill/AES,

On the 964, using the RS hub, you use the stock pulley's on the crank (no choice), with stock alternator belt, using stock pulley halfs and shims on the alternator shaft.

On the 993, using the RS hub, you can use either the RS crank pulley w/o a/c (993.102.050.40) or RS crank pulley with a/c (993.102.050.41), both using stock alternator pulley halfs, shims, and stock belt on the alternator shaft.