Underdrive Pulley Install Guide

[tommy986]

anyone know the torque spec for that bolt holding the pulley?

[Adam]

Did you happen to take a picture of the new and old pulley next to each other or weigh them? Is there a reduction in size, weight or both? Why only change the crank pulley and not all the accessary pullies, seems like there would be a more profound effect and free up some more hp?

[sd_boxster]

Originally Posted by Adam

Did you happen to take a picture of the new and old pulley next to each other or weigh them?

Nope.

Originally Posted by Adam

Is there a reduction in size, weight or both?

Both. I bet you're gonna ask me to quantify it for you, but I can't.

Originally Posted by Adam

Why only change the crank pulley and not all the accessary pullies, seems like there would be a more profound effect and free up some more hp?

I'm not sure how much you can underdrive each specific system - but underdriving the crank pulley does them all at once, rather than having to replace each accessory pulley. I'll have to defer to the experts - like Jaay, Jake, and others - I'm just a guy who bought one and installed it.

[Boxster586]

Originally Posted by Adam

Did you happen to take a picture of the new and old pulley next to each other or weigh them? Is there a reduction in size, weight or both? Why only change the crank pulley and not all the accessary pullies, seems like there would be a more profound effect and free up some more hp?

I realize this is an old post but wanted to add a little information for those who may later come across this thread like I did.

I installed my RSS pulley last night. I weighed the factory crank pulley - 327 grams. The RSS under drive pulley on the right is smaller but weighed more at 376 grams.

[MikenOH]

Originally Posted by Boxster586

I realize this is an old post but wanted to add a little information for those who may later come across this thread like I did.

I installed my RSS pulley last night. I weighed the factory crank pulley - 327 grams. The RSS under drive pulley on the right is smaller but weighed more at 376 grams.

Had a chance to drive it yet and notice any difference?

[Boxster586]

Originally Posted by MikenOH

Had a chance to drive it yet and notice any difference?

Hello Mike-

I did take it out for a short drive. I believe it IS the best $219 (includes new shorter belt, pulley tool, and shipping) I've spent on this car. Peppier in the lower rpms. Can't really tell above 5500 rpms. I need to get back on the track to confirm as I have zero access to a dyno.

Have a good week.

[ilikeching]

Originally Posted by Boxster586

Hello Mike-

I did take it out for a short drive. I believe it IS the best $219 (includes new shorter belt, pulley tool, and shipping) I've spent on this car. Peppier in the lower rpms. Can't really tell above 5500 rpms. I need to get back on the track to confirm as I have zero access to a dyno.

Have a good week.

Lighter rims & wheels will definitely feel the difference too, much more peppier at low rpms.

[jb92563]

Someone had said that there would be no AC at idle with a 4" UDP, so I thought I'd post my results to clarify.

I installed my Tarret 4" under drive pulley and all went well and better than predicted.

Particularly, I am happy to report that a 2001 S with the 4" under drive pulley still allows full operation of the air conditioning at idle!

Here is the Proof below:

With the Tarret UDP installed and the engine up to full operating temperature,
Ambient temperature 70 F as shown on the guage, and ~750 rpm at idle for over 5 minutes, airconditioning set at full the temperature of the air leaving the vent is ~38 F.


Tarret UDP and Original

[sd_boxster]

It's in the Bentley manual - I'll add it to the write up tomorrow, as it's too darn cold to go to the garage.

BTW - and I'll revise my writeup above - I read somewhere else that the crank pulley bolt should not be reused.

Originally Posted by tommy986

anyone know the torque spec for that bolt holding the pulley?

[sd_boxster]

Step 1: Torque to 37 ft-lbs.
Step 2: Tighten an additional quarter-turn (90 degrees)

Originally Posted by tommy986

anyone know the torque spec for that bolt holding the pulley?

[jmatta]

Thanks for the write-up, as this is a mod I'm currently considering (always need a spring project). Anyone know what the protrusion is for, that needs to be milled down? Almost looks like a point where a bolt would go to lock the pulley (not sure it lines up)...it must be there for a reason.

[JFP in PA]

It could be a couple of things; the M96 is used in multiple configurations, so it could be a mounting boss for something not use when in a Boxster. A lot of casting bosses on these engines are used as anchor or alignment points during initial machining operations in the factory, and not used again.

Considering its location so close to the factory pulley, it probably is not used when the engine is actually in the car.

[Topless]

I believe jmatta is right. The boss in the casing that must be cut down is a top dead center locator. You align to TDC and slip a retaining tool through the stock pulley to hold the crankshaft in place. It is useful when changing timing chain tensioners to keep everything aligned so don't cut it all the way off. There are other ways to fix the crankshaft at TDC but this is a quick way that techs are familiar with. On one car in our club the casing boss was completely cut off and the Porsche techs had to get creative as they could no longer use the tool.

[clickman]

Fig. 25 confirms it's for TDC.

http://www.pelicanparts.com/techarticles/Boxster_Tech/Disc163/BoxsterTech-163.htm

[jmatta]

Very good visual, indeed. Do you think the point is strong enough to hold so you could loosen the crank bolt? The only experience I have is that is remotely close is the tool that holds the pulley for removal in an older air cooled 911.