G/B for Underdrive pulley on CaymanClub

[insite]

10 - 15HP at the wheels is BS. Mantis (they race a Cayman S in PCA) has an underdrive pulley that fits all boxsters / caymans at mantissport.ca. they're good for 6HP, but the primary use is to slow the power steering pump slightly so the PS couplings don't melt (a problem on C7's and 987's in particular).

[easyc]

Common problem on 986S too!

[blinkwatt]

Originally Posted by cheetah

On many cars the crank pulley is a harmonic balancer also, but not on the Boxster. The stock piece is a very lightweight item, and only used to turn the accessories. My custom-made one has been on my car without any problems, and can be seen here:

http://www.cheetahonline.com/products/n8039.html

This is a 20% reduction, has been tested, and it works great. A noticeable increase in power throughout the powerband. The voltage has been tested with all the accessories on during idle for extended time without any drop in voltage.

This also takes 2/3 the power to turn the pulley, as it was made as lightweight as possible. I have not been able to dyno it yet, but I hope to soon.

Paul

How hard was the install? What tools were required? How many miles have you had it installed for now?

[blinkwatt]

http://www.caymanclub.net/reviews/showproduct.php?product=157

Should be the same concept on a 986.

[cheetah]

The installation was not hard at all. The Cayman directions are very close to that of the Boxster.

Socket set for the various bolts to get to the pulley. To take the pulley off there are a few ways:

1. Screw a bolt through the hole in the pulley and into the area that needs to be ground down. This will hold the pulley still to take the bolt off. (this is what the Porsche book recommends)

2. Use the Porsche tool or equivalent to hold the pulley still

3. Use a strap-wrench to hold the pulley still.

I actually prefer #3 as it won't leave any marks and can be used to mount the new pulley easily.

Once the pulley is held still, a 24mm (I believe) socket will need to be cut down shorter. I was able to get the racket in this tight spot to take the bolt off, but the torque wrench to put it back on just wouldn't fit.

Grind the ridge as shown in the other installation. Put new pulley on and reverse instructions. The new belt that I listed is used as the stock one will be way too long.

I don't drive the car everyday (third car), but I have put it through every conceivable test to watch voltage, coolant temperature, and steering response. The voltage is good even with full load, the temperature stays the same, and steering feels exactly the same. I also monitored these driving with the Durametric logging all the sensors.

As stated, this is a 20% underdrive.

Any other questions, feel free to ask...

Paul

Originally Posted by blinkwatt

How hard was the install? What tools were required? How many miles have you had it installed for now?

[Gary in BR]

Has anyone installed an underdrive pulley on their 986 yet?

[insite]

i just read the instructions for that install. FYI, that thing they grind off is actually kind of important during an engine rebuild. there's a pin that goes through the OEM pulley and that aluminum protrusion at six different positions required for proper reassembly of the motor.

[steve00s]

Thats pretty cheap HP compared to other things that we do. 5 HP is not much but neither is $200 and there is some benefit on the power steering issue too (not that I've ever worried about that). The reviews that I have read report no problems. I've had these on other cars I've owned and have kind of wondered why I didn't hear anything about them in the Porsche world. I'm buying one.

[mn box s]

Whooh! people are jumping around on this like crazy! This is my best at getting things straightened out. Ok of coarse a pulley kit won't increase boost do you know how a motor works? Pulleys have been known to throw off harmonics and wreck bearings. Pulleys also are very bad for people trying to run extra stuff electrically such as amps for stereos. Some one had checked their electrical current... was that also a load test? The fluctuation may be small but at higher revs becomes much greater. Over time wrecking your alternator. I'm almost certain the life of your alt. will be cut in half.... "but mine is fine." I know I'll here this yes I was guessing about half life or less more likely less. Say your alt. lasts 10 years normally 100k miles I'd almost put money on the fact that you will get another 30-50k on it now, not 100k. It is interesting about the power steering and I can see how it would help. Remember this is on track cars that this would benefit and they usually have less extra electrical stuff than you would have on the street other than af computers and things. 10-15hp that has to be an @ the crank "claim." You will feel more power in the throttle with pulleys thats not the argueement. Now lets look at the other side of the crank. I would hope everyone on here knows whats on the other side but if not... its your flywheel. I want to say its about 30 freaking lbs! I bet you can find one for 15lbs or less. Think that would be a better weight savings on your rotational mass? Best bet go all out get a light weight fly and pulley kit, strip your car down to a hyundai, track your car like a champ and buy alts. once every year. Oh and pray the part doesn't cause the dreaded gingivitis oops, I mean RMS. Know one worries about RMS do they.

[steve00s]

Could you be a little more specific? I understand problems about increased load on power amps and such but I do not understand this comment:

"The fluctuation may be small but at higher revs becomes much greater. Over time wrecking your alternator."

Is this assuming that one is powering additional power amps?

[tholyoak]

As insite points out, the installation of these pulleys requires grinding down a casting on the case. The one thing you may want to consider is if your motor ever requires replacement you run the risk of Porsche not accepting the old engine as a core in return for a Porsche reman unit as your core is now no longer acceptable as a rebuildable unit. You may get lucky and they won't notice it, but it could turn out to be a several thousand dollar mod down the road if they do.

As mn box s states, if you are simply looking to free up some HP, you are better off replacing the dual mass flywheel. If you are just looking to save the ps pump lines from failure at the track, simply reduce the pulley size on the ps pump.

Just something to consider.

Todd

[Frodo]

Quote:

"As mn box s states, if you are simply looking to free up some HP, you are better off replacing the dual mass flywheel. If you are just looking to save the ps pump lines from failure at the track, simply reduce the pulley size on the ps pump."

Posted by tholyoak.

Uh, unless I'm mistaken you're going to need to increase the pulley size on the ps pump.

[tholyoak]

Sorry, my mistake, you are obviously correct.

Todd

[Frodo]

Apology accepted.

Just don't let it happen again.