986 2.5 underdrive pulley dyno graph

[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.

[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