Still trying to find out. Did you guys reuse the old bolt that was holding down the oem pulley?

I re-used the original bolt, not issues as of today (1 year and a few thousand miles). I also re-used the original belt, it was in almost new shape. When the belt is due I will however go for a slightly shorter one.

I think I'm going with this one
http://www.tarett.com/items/boxster~cayman-products/986-987-engine~transmission~brakes-/under-drive-pulley-udp-detail.
Comes with The tool, the belt and the bolt.

Project...
You can use the old bolt but a new one is less than $5 from Porsche.
If you use the original bolt, I would recommend cleaning the threads (including the internal threads in the crankshaft) with alcohol or thinners and then coating with Loctite thread locker.
Torque bolt to 50 Nm PLUS another 90 deg of your torque wrench (from positions 12 o'clock to 3 o'clock).

This may have been addressed in an earlier thread, but does cutting off this boss on the block prevent you from locking the cams in place? I thought i saw that somewhere.

Mike, what you probably read was that if you fit the smaller UDP, there is no hole in the pulley that lines up with the hole in the crankcase boss to lock the cams.

After saying that, you are not completely cutting off the boss, only trimming it about 5mm to clear the new pulley.

FYI to all doing this mod the piece to trim cuts like butter, the access isn't wonderful but it cuts so easily it's one of the easiest mods I ever did. Regarding the use of the old bolt, I used mine and see no reason for concern in reuse unless the item is in poor condition.

On the RSS, the belt portion of the pulley runs right over the top of the hole in the boss. NO way to utilize the hole. I figured I would put the old one back on if I needed to lock it down. I also reused my attaching bolt no real problem noted. RSS came with a holding tool to tighten the bolt.

I'd also quite like to ditch the aircon kit in my car - do any of the UDP makers offer a no-aircon belt?

Do a search here, I posted a link with the different belt lengths.....!!

HELPFUL HINT: What size serpentine belt to run when using an under drive pulley? - GSR Autosport Community

Here you go!

is anyone familiar with the Mantis UdP?
how is it compered to the RSS or the BBI?

It was one if the first things I did to my car. A lot of Cayman guys have the Mantis. Check out Planet nine. It was one of the first available. Apparently it was tested and gave 7-8 rwhp.

Mine was solid, black anodized. Looked very high quality; it's solid and heavy. The BBI is light and spoked. I am unsure of the relative polar moment of inertia. If it is significant then the bbi would give you more of a light flywheel effect where as the Mantis more flywheel momentum smoothness. I doubt this effect would be noticeable

At the time I did notice a feeling of more power. I desnorked at the same time so I might have been up 10 hp

Go with dummy pulleys from BGB

This info may help with selecting a shorter belt:


Hello Johnny.

If you can be sure (confirm with a Porsche dealer if you'd like) that your Boxster uses the same belt as my 2007 Cayman S then yes, the Gates K060820 should work fine.

If you'd like to play it safe, take you OEM belt in to your local auto-parts store that sells Gates and tell him you need a similar belt but about 30mm to 38mm shorter. My stock 2007 Cayman S belt measures 2113mm, Gates part #K060832.

Gates offers the same belt design in neighboring lengths of 2098, 2082, 2071 and 2058 mm. The 2082 mm (31mm shorter than stock) seems to be the best length based on the calculation of the under-drive pulley circumference. For future reference this Gates belt is #K060820.

Regards,
Joe