986 2.5 underdrive pulley dyno graph

[Steve Tinker]

Bobiam,
I can't comment on the OP's choice of pulley, but I fitted the Raby pulley 3 months ago and its not the HP increase (which according to the graph is minimal), but the torque increase from low revs that has impressed me. Yes, you can definately feel it in the seat of the pants, especially from 1,500 - 5,000 rpm, after that it academic....
As an additional bonus, the cabin is much quieter due to lower accessory rotational noise....

[Gilles]

Bobiam,

Two years ago I installed a (BBI) UDP, the main reason was to reduce the accessories because I was overheating the steering pump at the track.

The first failure was the high pressure fitting at the steering rack, the second failure was melting (somehow) the bottom of the reservoir with an o-ring failure and lastly the dealer ended replaced the PS pump along with some of the high pressure lines that were damaged when the hot fluid leaked.

However, I am planning to install a cooler on the low pressure return line (along with an Accusump) before heading back to the track
.

[Jake Raby]

Smart people understand the torque increase is where its at...

[chaudanova]

Originally Posted by Jake Raby

I have been developing a harmonically dampened UDP for over two years now.. As soon as I saw the other companies making similar companies I halted the development because theirs is cheaper and few people buy "better" these days.

Jake,

Seeing as you stopped development of the dampened UDP, can you give an honest breakdown of what you think between the 4" undampened unit that you have been using lately, versus the aforementioned dampened unit that Cloudsurfer installed by RSS? (Even if you haven't had a chance to get your hands on the other unit in person yet, perhaps you could give me a theoretical comparison).

I don't know the dimensions of the RSS unit, but am curious if going with the smaller and lighter 4" UDP, has more benefits than the perhaps larger and heavier dampened unit...

Please feel free to PM me if you think this would start any unnecessary controversy. I'm very open-minded, and since I would like to install an UDP soon, I would just like to know the pros/cons before going with a particular unit.

Thanks in advance

[Jake Raby]

I haven't stopped the development of the dampened UDP. We are still working on the project as an exclusive product for our updated engine program.

[Bobiam]

I really like the concept of the UDP, but it's difficult to determine the right one to install.

We're debating dampened vs not dampened. Although Jake is interested in developing a dampened pulley, the one that he's been selling (now out of stock) is not dampened. I've looked over the BBI and the RSS and they do not appear dampened (per photos) and I can't find descriptions to say one way or the other. Dampening is adding a complexity, a cost, weight and perhaps a failure point, so I'd say, if you don't need it, don't do it.

Next, there is % underdrive. BBI says 16%, Jake's people said they weren't sure, and RSS is 15%. I'm sure that you can only do so much underdrive % on a street use car before something doesn't work right. But which something, and what affect will that have (electronics, cooling, power steering at idle)? I'd stay on the conservative side on this issue!

On the other hand, contributors to this forum have shared success stories, so far.

My mind is not made up yet!!!!! Need more info.

Bob

[cheetah]

I contacted RSS and asked them about this. Below is their reply:


The resulting noise from using a single mass aluminum flywheel will not be reduced by using a dampened pulley. The only way to eliminate the chatter is to go back to a dual mass or heavier flywheel. A dampened crankshaft pulley is designed to dampen engine harmonics. The resulting chatter is from the transmission, hence the pulley will not make a significant reduction in Gear Chatter.

[chaudanova]

I keep asking the same question, but can't seem to get a proper answer.

Pros/Cons between 4" Flat6/Raby/Amond pulley vs. RSS dampened pulley... ?

[Cloudsurfer]

The dampened pulley is not to quiet chatter of the flywheel/ clutch assembly spinning in the bellhousing. It is to quell engine harmonics (especially major criticals, of which every engine has one or more at various RPMs- keep an engine at the major critical RPM long enough and you can snap a crank).

Porsche never installed a harmonic damper on these motors until the M97 3.8. As soon as you remove the dual mass flywheel, there is now NOTHING to dampen ANYTHING. Adding the harmonically dampened pulley allows for some damping factor on the engine, which when running a single mass flywheel, is pretty important in my opinion.

As to the pros/cons regarding the added weight of the dampened pulley, that downside falls very distant compared to the pro of adding engine reliability/ longevity.

If anyone would like further reading about harmonic dampers, Steve Dinan has an excellent section on his site, referenced with the following link:

http://www.dinancars.com/bmw/technial-info/the-dangers-of-power-pulleys-and-understanding-the-harmonic-damper

[Gilles]

Originally Posted by Cloudsurfer

If anyone would like further reading about harmonic dampers, Steve Dinan has an excellent section on his site, referenced with the following link:

http://www.dinancars.com/bmw/technial-info/the-dangers-of-power-pulleys-and-understanding-the-harmonic-damper

Great reading, thanks for the link

[amondc]

I have had a pulley on my spec boxster for over a year now with no problems. I have installed several on street and track car and had no issues. I believe that Jake put one on his street boxster and ran a/c, radio, etc all in "street" conditions and found no ill effects.

Chris

Jake
If you need some more let me know.

[2K3_Boxster_S]

Originally Posted by chaudanova

I keep asking the same question, but can't seem to get a proper answer.

Pros/Cons between 4" Flat6/Raby/Amond pulley vs. RSS dampened pulley... ?

Cons: 4" Flat6 pulley.

you can't buy one. I've been trying for last 2 month's every time I go to website the store is Closed for inventory. How long does it take to do inventory?

[amondc]

Email me chris at texasspec dot com. I'll get you taken care of.

[cheetah]

This is the RSS dampened underdrive pulley for a 3.8L on my 3.4L swap in my 02 Boxster S. I am just waiting on an air filter (making a custom airbox for it), and then it is off to the dealer for a re-flash and alignment).

[2K3_Boxster_S]

Originally Posted by cheetah

This is the RSS dampened underdrive pulley for a 3.8L on my 3.4L swap in my 02 Boxster S. I am just waiting on an air filter (making a custom airbox for it), and then it is off to the dealer for a re-flash and alignment).

Please tell where to get the dampener or dampener/pulley combo. I checked RSS website and could only find the pulley itself.

I'm doing a LWF and will need it badly.

[Cartel]

Originally Posted by 2K3_Boxster_S

Please tell where to get the dampener or dampener/pulley combo. I checked RSS website and could only find the pulley itself.

I'm doing a LWF and will need it badly.

It is an item not yet advertised on their website. Call 714-545-1046 tomorrow, and ask for Bryan, tell him Carlos sent you. They have been an absolute delight to deal with thus far, and are more than accomodating, near to the likes of the folks over at FVD Brombacher.

[2K3_Boxster_S]

Originally Posted by Cartel

It is an item not yet advertised on their website. Call 714-545-1046 tomorrow, and ask for Bryan, tell him Carlos sent you. They have been an absolute delight to deal with thus far, and are more than accomodating, near to the likes of the folks over at FVD Brombacher.

Thanks, I'm still trying to source a quality clutch that has a sprung disc made from decent material for the 3.2.

[Cloudsurfer]

Originally Posted by 2K3_Boxster_S

Thanks, I'm still trying to source a quality clutch that has a sprung disc made from decent material for the 3.2.

SPEC, Stage 2 is recommended.

[Cloudsurfer]

Originally Posted by cheetah

This is the RSS dampened underdrive pulley for a 3.8L on my 3.4L swap in my 02 Boxster S. I am just waiting on an air filter (making a custom airbox for it), and then it is off to the dealer for a re-flash and alignment).

Aren't you glad I suggested this

[cheetah]

Yes I am, as I didn't even know it existed.