Underdrive Pulley Install Guide - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Boxtaboy · 12-13-2009, 10:10 AM

Thanks for the write up. I also would like to know what your experience is after doing this. Notice any extra power or other improvements?

sd_boxster · 12-13-2009, 10:41 AM

Just got back from a decent drive. There is a noticeable performance gain - not enormous, but appreciable. Certainly more than I "gained" from my EVOMS intake.

Interestingly, all of the accessories running at a lower speed results in less overall noise. Maybe this is due in part to the new belt - but whatever the cause, I'm very happy with this side effect.

So - I'm happy! Hopefully I'll get an AX in sometime soon and get back with a proper review.

amondc · 12-15-2009, 07:40 PM

Looks good Glad the install went well.

Chris

tommy986 · 12-15-2009, 08:01 PM

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

Adam · 12-15-2009, 08:47 PM

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 · 12-15-2009, 10:21 PM

Quote:

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.

Quote:

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.

Quote:

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 · 08-19-2012, 10:15 AM

Quote:

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 · 08-19-2012, 04:33 PM

Quote:

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?

sd_boxster · 12-15-2009, 10:13 PM

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.

Quote:

Originally Posted by tommy986

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

sd_boxster · 12-17-2009, 07:48 PM

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

Quote:

Originally Posted by tommy986

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

jmatta · 12-31-2009, 07:05 AM

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 · 12-31-2009, 08:00 AM

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.