Revisiting the underdrive pully topic for fresh info.
 

I'm going to install a UDP soon, and want to get everyone's take on the "latest and greatest." My primary reason for installing the UDP is to hopefully prevent damage to my power steering system. I get a few track days in every year and have noticed the power steering fluid get low at times. Of course, I'm not going to deny a couple extra HP would be nice, but that is secondary for my priorities. I'm mainly hoping to save money on future repairs. Along those lines, I may also install the LN power steering fluid cooler.
UDP manufacturers have come out with a few designs. Ideally, I'd get the lightest, smallest pulley. It seems to me like there have been no ill side effects with even the smallest pulleys out there. So who makes the smallest and lightest one out there? I think I read the BBI unit is a 16% reduction, and the RSS is 15%. Can anyone confirm this? Is there any other one I should consider?
I know there has been a lot of talk about this, but didn't see any recent posts. With how quickly things like this change, I thought there may be a newer or better option out there. Again, my priorities are to have a significant decrease in accessories speed. Yes, I understand there may be ill side effects if I go too much in that direction.
Thanks guys!:dance:

I have the BBI pulley on my vehicle . Although I can't say for certain what the actual reduction in weight is, the quality and design of it was nothing short of remarkable . In addition, the people at BBI were great to deal with . I highly recommend it .

FWIW, the percentage figures I listed are reduction in drive, not weight. While weight reduction is nice, it is far less significant to me than drive reduction.

I fitted the Flat6 UD pulley two years ago - the only negative is a slight voltage drop from the Pternator @ 850 rpm, but it regains back to Porsche specs (13,5v) @ 1,500 rpm - no issues to date.
Its the best bang for your buck currently available......

My mistake, I thought the percentages that you were referring to had to do with weight . In any case, I found the following info based on a 996 application:

Weight;
Stock - 860.1 grams
BBI - 200.5 grams

Crank snout engagement depth;
Stock - 7.5mm
BBI - 14mm

Overall Diameter;
Stock - 142mm
BBI - 115mm

HP Gains;
8-12.5 WHP

We are proud to say that this is 100% made in the USA...From the materials to the machining and the anodizing.

Don't overthink the pulley. It does improve the life of PS pumps and probably alternators as well on cars that spend a lot of time in high rpm. Remember that the smaller the pulley, the slower the water pump turns so there are practical limits. It does lessen the parasitic loss from running the accessories but dyno results from the Boxster spec series looked like it was in the 3-5hp range. Finding a real 12hp with an UD pulley is the stuff of fantasy. A well balanced pulley is probably far more important than getting the absolute smallest.

Thanks, JD. I'm not confident those numbers also apply to the Boxster pulley. I certainly hope they do, though! :)
Those figures show a 19% reduction in drive, and a bigger HP bump than I've seen claimed elsewhere. The dynos I've seen with the Boxster UDPs seem to be up 6 to 7 CHP.
Your thoughts? It would be great if this also applies to the Boxster.

Thanks, Topless. The BBI pulley looks very well balanced in their testing. I get the impression like you think the UDPs are all pretty much the same. Also, I am of course concerned the with practical limits you speak of. That said, I don't get the impression I would bump into any of these limits with the offerings currently available. That's why I am trying to split hairs here.
Do you know which pulley the BSX cars are using, and what the drive reduction is?
TIA

Both BSR/BSX classes allow any underdrive pulley with a minimum diameter of 4". I am guessing that someone, somewhere calculated the change in belt speed and determined it was a good compromise between slowing the accessories while preserving coolant velocity. They have been well tested over the last 3 years in a lot of track miles with good results.

Do any of the kits come with tools to help with installation? I've seen some rigged-up tools to keep the pulley aligned during removal/installation.

I believe all of the UD pulleys require a boss on the block to be trimmed off, due to the location being inside the stock pulley diameter. If there is an option that doesn't require this to be cut off but still has decent UD, I'd be interested in looking at it - anyone know if this exists?

The 996 stats were the only ones that I could find . I imagine that the figures for the boxster are different . How much is unknown ? However, I would agreed on the 6 to 8 hp gain though .

I have te RSS UDP, it came with the installation tool. My understanding is that the boss has to come off with any of the UDPs. I tried my Dremel but that was slow so I took a saw. One note, get the right wrench to loosen the the bolt, that was the hardest part, lots of elbow grease needed!
Also, I reused the original belt it was in great shape and it works just fine. Eventually I will replace the belt with a slightly shorter one once due.
So far no ill effects whatsoever! There is def some gains, and as mentioned a million times best bang buck mod.

Later,
Andy

Hello. I recently bought an RSS under drive pulley. Kept buying stronger tools with more leverage but I cannot get the old pulley off. Bolt is too tight.

Any help or DIY guides on that?

The RRS UDP came with that tool, but I do not know how to use that tool or why that tool is needed.

What do you guys mean when you say boss or block? And what do you mean when you say it is hard to align the pulley?

I thought all I had to do is remove the bolt holding the old pulley, pull it out, and insert the new pulley+belt.

The tool is for holding the original pulley in place so that you can get the bolt undone. As I mentioned in my earlier post the bolt is VERY tight and you need a lot of force.

The "boss/block" is part of the engine block. Due to the different design of the original pulley and the RSS pulley this boss is in the way of your new pulley and has to come off, you'll see! Use a hacksaw, much easier than a Dremel or such.

Basically totally easy to do, bolt is the hardest part....

Good luck!

You are going to need a different belt when you finish as well.

Already have the updated smaller belt for the RSS UDP.

Did you guys reuse the pulley bolt? I read on one of the UDP manufacturer sites that you need new bolt and should not reuse the old bolt.

My Wrench is 14 inches long so it has lots of leverage, but I still couldn't get that bolt open. I will hit the wrench with a hammer to see if that helps.

So is it easy to saw off? RSS said that it was an easy installation no extra tools required. Liars.

i am getting ready to do this and i went with the RSS kit and shorter belt. I have not installed it yet , hopefully soon .

I'm interested in this as well. Where do I buy the kit with the pulley, belt, and tool?

BBI AutoSport, Road Sport Supply and Jake Raby all offer excellent LWUD pulleys .

Guys, yes that bolt is on there tight, but it was a very simple removal using leverage.

Use your ratchet, or better yet, breaker bar, coupled with a long stick/pole. I used the long metal one that is used on floor jacks (depends on the type you have). Mine was perhaps roughly 3-4 feet long with a hollow end that I was able to slip over the ratchet/breaker-bar. Didn't require much force to remove at all, using this leverage.

And if you don't have the pulley holding tool, depending of the type of pulley you purchased, you may not even need one. For the 4" pulley I installed, I just slipped a bolt through one of the holes in the pulley through the hole in the block to hold it in place.

Hope his helps!