986 2.5 underdrive pulley dyno graph - 986 Forum - The Community for Porsche Boxster & Cayman Owners

violametallic-S- · 04-17-2010, 07:11 PM

nice results. I have my pulley sitting in a box for my 3.2, waiting for a nice day to install it.

Cloudsurfer · 04-17-2010, 08:34 PM

RSS also makes a harmonically dampened underdrive pulley, designed for the M97 3.8 motors, that fits just fine on any of the rest, provided you use the longer bolt.

Seems like a pretty good idea to me to get some damping onto the crank in these things.

edevlin · 04-18-2010, 02:48 AM

"RSS also makes a harmonically dampened underdrive pulley, designed for the M97 3.8 motors, that fits just fine on any of the rest, provided you use the longer bolt. Seems like a pretty good idea to me to get some damping onto the crank in these things."

would this help those of us with lightweight flywheels to dampen some of the harmonics normally handled by the DMF?

Ed

Cloudsurfer · 04-18-2010, 07:41 AM

Quote:

Originally Posted by edevlin

"RSS also makes a harmonically dampened underdrive pulley, designed for the M97 3.8 motors, that fits just fine on any of the rest, provided you use the longer bolt. Seems like a pretty good idea to me to get some damping onto the crank in these things."

would this help those of us with lightweight flywheels to dampen some of the harmonics normally handled by the DMF?

Ed

Yes. Hence why it's on my motor

chaudanova · 04-18-2010, 01:27 PM

Cloudsurfer, what are your driving impressions with the harmonic RSS unit?

Cloudsurfer · 04-18-2010, 03:18 PM

Quote:

Originally Posted by chaudanova

Cloudsurfer, what are your driving impressions with the harmonic RSS unit?

Not sure yet, I'll let ya know once I get the car running again!

Boxster44 · 04-20-2010, 06:57 AM

Ed,

What clutch did you use with the LW flywheel? I opted for the Sachs 6 spring clutch to (hopefully) mitigate possible harmonic issues.

kj

Jake Raby · 04-27-2010, 05:47 AM

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 · 04-27-2010, 06:11 AM

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 · 04-27-2010, 10:34 AM

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.

pothole · 08-07-2011, 06:43 AM

Quote:

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.

and

Quote:

Originally Posted by 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.

Sorry, confused, which is it?

Further questions are - is there any value in a damped pulley on an early 986 should I choose to go with an underdrive item and is the Flat-six Innovations the smallest UDP currently available? How much smaller than standard is it? I think it's 4-inch - how much smaller is that in percentage terms? 20%?

Thanks