Underdrive Pulley Install Guide

[sd_boxster]

I just finished installing the 4" underdrive pulley that forum member Jaay sells, and I documented the process in varying degrees of detail to help anyone else out who's considering this mod.

Tools required:
Jaay's 4" pulley and belt
10mm socket and driver
24mm shallow socket
Breaker bar for above
Grinder, dremel, or hack saw
Porsche crank pulley removal tool (or see below)
Various common hand tools
Highly recommended: A pair of mechanic's gloves

Remove your rear subwoofer or whatever other accessory you might have on the rear shelf so you can get the carpet kit out of the way. Slide both seats all the way forward.

Remove the four plastic anchors so you can move the firewall carpet/insulation panel.



You will see the engine cover.



Remove the 10mm bolts and the two 10mm nuts around the perimeter of the cover.



Once you remove the panel, you will see the pulley to be replaced with the underdrive version - it's the pulley below the belt tensioner.

[sd_boxster]

Use your 24mm socket and breaker bar to crank on the belt tensioner so you can remove the existing serpentine belt.



Get out your Porsche crank pulley removal tool, or be prepared to bust something out on the fly. You need to use the 24mm socket to loosen the bolt holding the crank pulley. It's tight.

Since I didn't have the Porsche part, I made something out of a bolt, my floor jack handle, and some plumber's tape I had on my workbench by fishing the bolt up behind the OEM crank pulley, adding a couple of nuts, and creating a strap to attach the jack handle to the pulley... Hopefully the pics explain better than this text...

First, I fished the bolt up behind the factory pulley. I taped a zip tie to the bolt so I could pull it through the hole.



I used another nut to secure the plumber's tape to the factor pulley.



This image sort of depicts how I used the jack handle for leverage, and the socket on the crank pulley bolt as a fulcrum, to get the bolt loose. The jack handle is in the wrong place in this image - it should be ABOVE the socket (lefty-loosey), but you get the idea:



With the old pulley out of the way, it's time to cut down the boss to make room for the new UD pulley. You can see in this pic the material that needs to be removed. I took off about 3/8" to make the boss flush with the other protrusions on the engine case.

I started out using a dremel, but the best tool I had for this job turned out to be a small hack saw I picked up at Home Depot a while ago - it looks like a stout coping saw and works great for cutting at an angle.



Install the new pulley. EDIT: At least one other write up I found indicated that the crank pulley bolt is not reusable.



This image shows the clearance between the cut-down boss and the new pulley. Make sure you remove enough material so the boss does not interfere with the pulley...



I used a strap wrench on the new pulley so I could apply the requisite torque (i.e. I "tightened the snot out of it" per Jaay's instructions!).

Use a shop vac or other means to remove any shavings you created while cutting down the boss...

Install the new belt (refer to your Bentley to ensure you get the belt routed correctly!).



Once you have cranked everything down and triple-checked the belt routing, fire up the motor with the cover off to verify that things look right. Specifically, make sure the new pulley is flat and unobstructed.

Shut the engine down and perform one last snot-tight torquing on the crank pulley bolt.

That's it! This took me about 2 hours, including taking pictures, lashing together my ghetto pulley tool, and drinking several beers.

[tnoice]

nice write up. Did you notice a substantial improvement?

[Boxtaboy]

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]

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]

Looks good Glad the install went well.


Chris

[notworthy]

I just completed my installation of the updated Mantis Sport underdrive pulley. The engine feels a bit more free and when I say a bit, I really mean just a bit. Good value mod though. The hardest part was cutting the boss, everything else was really straight forward. I actually got the pulley for free, and got the belt for $52, so a nice inexpensive mod.

Thanks for all the technical data and installation steps, they made the job really easy for me.

[rokketdawg]

I just bought a TRS underdrive pulley and just wanted to know how the hell you got any of the tools in there to do this. Does anyone have pics of the crankshaft removal tool...specifically the tool that uses the threaded bolt to push against the crank to force the pulley off of the tip? I'm sure this must be a shorter threaded bolt than the average kit you can find in any auto parts store, but pictures would go a lot further to explain that part of this process. Thanks!

[Supermini]

Hey guys, great guide here with pictures and everything!

you dont need a special tool to remove the factory crankshaft pulley, i found an old bolt that was the correct width to push through (dont need to thread it) one of the holes on the pulley into the boss (which later you have to cut off). this will stop the pulley from turning allowing you to undo the nut.

then removing the pulley is a case of gently levering it off with a long screwdriver.

i bought this one


Crankshaft Pulley Kit (For cars with AC)


I can feel the difference, it is a small gain, but its worth it.

[rokketdawg]

Can anyone explain how they torqued the new bolt down without having a hole in the pulley to lock it in place?

[jb92563]

You need a pulley that has at least one hole in it so you can use a bolt, but if no hole then you will need to clamp it with a vise grip and some pieces of wood to protect the pulley.

Having driven my Tarret 4" UDP for a few days now I'm very pleased with what feels like extra torque and power.

It also seems like the engine sounds smother and quieter.

The extra torque in first gear needs a bit of getting used to, as it was raining this morning and I have been getting a bit of tire spin using my old familiar technique.

A little slower application of throttle in the wet is required.

Overall, I have to say it was a much easier install than I thought it would be, although grinding off the casting protrusion was a pain because I did not have a right angle grinder that would fit in that tight area so I had to use an airtool saw and file to get at it and tidy it up.

A 90 degree die grinder air tool with cutoff wheel would have been the perfect tool to get in there and get it done quickly without fuss.

No problem getting the old pulley off either as the shaft is not tapered so simply prying it off with a long screw driver is all that is required.

You also need a cheap 24 mm socket and cut it down to the minimum to go over the bolt head with a grinder as its a tight space in there and not much room for the socket and wrench.

Well worth the ~$200 and perhaps the most HP bang for your buck of any mod you can do to a Boxster.

[jsceash]

Originally Posted by rokketdawg

Can anyone explain how they torqued the new bolt down without having a hole in the pulley to lock it in place?

RSS supplied a wrench with the pulley kit. Kit included a belt pulley and a pin type wrench.

[jsceash]

I had to remove 1/4" of the boss Plenty of hole depth left.

[Quadcammer]

about to do this mod and well I'm a bit confused by something.

The crank pulley looks like it slides over a keyway. If you leave the car on the ground and you put it in 5th gear with the parking brake on, the crank shouldn't turn, hence there should be no issue with removing or tightening the bolt.

Am I missing something?

Thanks

[JFP in PA]

Originally Posted by Quadcammer

about to do this mod and well I'm a bit confused by something.

The crank pulley looks like it slides over a keyway. If you leave the car on the ground and you put it in 5th gear with the parking brake on, the crank shouldn't turn, hence there should be no issue with removing or tightening the bolt.

Am I missing something?

Thanks

Tightening the crank bolt is not the issue, but if and when you go in for an IMS swap, or some repairs involving resetting the cam timing, be prepared for a significant up charge as the shop is going to have to remove the under drive pulley and reinstall a factory unit in order to lock the crank at TDC, that is assuming you have not removed too much of the pin boss from the engine cases when you installed the pulley. If you did, the trans will have to be pulled so that the engine can be locked at TDC from the flywheel. Oh, and the latter adds roughly $3K to the bill of whatever else is being done.

[Quadcammer]

Originally Posted by JFP in PA

Tightening the crank bolt is not the issue, but if and when you go in for an IMS swap, or some repairs involving resetting the cam timing, be prepared for a significant up charge as the shop is going to have to remove the under drive pulley and reinstall a factory unit in order to lock the crank at TDC, that is assuming you have not removed too much of the pin boss from the engine cases when you installed the pulley. If you did, the trans will have to be pulled so that the engine can be locked at TDC from the flywheel. Oh, and the latter adds roughly $3K to the bill of whatever else is being done.

Thanks for the tip. Pretty sure I will have enough of the boss remaining the crank at tdc.

That doesn't answer the question of why the crank is turning during this job...it shouldn't be

[geetee]

you seriously cannot remove too much of that boss. It's pretty deep. The center hole extends in deeper than what you can cut off.

[JFP in PA]

Originally Posted by geetee

you seriously cannot remove too much of that boss. It's pretty deep. The center hole extends in deeper than what you can cut off.

Don't bet on it. We have had cars come into the shop with the entire boss hacked off, which allows enough slop in how the pin holds the pulley to make it all but useless.

[Quadcammer]

I hacked off a decent amount of the boss, but there is definitely plenty left, even with excellent clearance to the pulley. Not too concerned about that.