986 2.5 underdrive pulley dyno graph
 

i have just installed the RSS underdrive pulley and had gotten it dyno tested today. The car is a 97 boxster 2.5L. I think some people will be interested in the results. it started at 199hp for the first run. they had pulled it 5 times and every time i had gotten about 1-2hp more. i called it after the fith pull because it was starting to get hot. the final result was 206.5. When it was stock i had dyno tested at 200.9-201.1hp.

[IMG]IMG]http://i899.photobucket.com/albums/ac197/transtlye/1271541660420.jpg[/IMG][/IMG]
http://i899.photobucket.com/albums/a...1541645936.jpg

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

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.

"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 :)

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!

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

Not bad - Note that Dyno Dynamics dynos tend to read 10 - 15% lower than Dynojet dynos, which most aftermarket manufacturers use to make their dyno claims.
Dyno Dynamics are excellent for real-world tuning.

SPEC Stage 2 (sprung center) with Aasco flywheel.

Continually we see exactly 12-15% variations between either of my engine dynos with the same engine installed into the vehicle and evaluated on our dyno-jet chassis dyno. This is the same differentials with either air-cooled or water cooled Porsches.

I am less concerned with actual peak numbers than most any person you'll meet. Our dynos were bought to be developmental tools so repeatability trumps any peak number.. Last week I did 5 runs back to back on the dyno jet and attained less than .75 HP of differential across the entire average RPM range. That repeatability is whats necessary to do the level of developmental comparison that I am interested in.

a question for Jake regarding harmonic issues.
 

Jake,

I was very interested on installing the LWFW along with the Sachs spring clutch disc but got cold feet after reading one of your posts where you mentioned that the dual mass flywheel cancels the harmonic issues and that there were several engines that failed because the dual mass FW was replaced with a LWFW.

Do you think that would be safe to install a LWFW (AND) an underdrive crank pulley with a harmonic balancer?

I saw an ad from a company called ATI Racing and they told me that it was possible to manufacture an underdrive pulley with a harmonic balancer.

However, I was not aware of the RSS UDP until this post, but the ones from ATI seem beefier.

Somewhere I read that some of the older Porsche engines had a harmonic balancer build into the crank pulley as well, but I am not sure if these would fit or if they would do the job once done by the dual mass flywheel.

What do you think?

Regards,
Gilles

PS, this is the link to ATI:

http://www.atiracing.com/products/dampers/damper_tech.htm

.

ATI makes great stuff, unfortunately they do not have any applications that would benefit us, hence why I went with the RSS unit.

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.

aint that the sad truth

So, overall for the 986... What would be the pros/cons now, choosing between the RSS pulley with the harmonic balancer versus the 4" Pulley from Raby/Amond?

Would the extra weight of the dampened unit be a disadvantage, or is it mostly the size/diameter of the pulley that is more of a factor in its effectiveness?

Jake,
Do you think that would be OK to install a LWFW (with a Sachs spring disc) as long as a harmonically dampened UDP is used as well?

I'll certainly take the damping effect over saving a tiny bit of weight.

I'm also really interested to get some quality feedback on clutch/flywheel upgrade ideas and what is good vs what is asking for some kind of problem..I too have read those threads on people putting in LWFW and then having some kind of motor failure.... My car is approaching 80k and I can feel some vibration when I engage the clutch...the grab is still okay, but not as good as it used to be, so I know a clutch is in my future.. not sure if the flywheel has to be redone, replaced, or what when my clutch is replaced.

putting in a LWFW *and* an underdrive pulley would be anice way to make my 2.7 more peppy....but I don't want to do something that makes the car likely to have any major failures....

what is the consensu on these parts...particularly teh LWFW?

I'm not trying to be critical or anything, but a max 5.5 HP gain (less than 3%) does not seem worth the effort/cost. Do you feel there is a noticable difference in the seat of the pants? I was thinking about a Raby UDP but am hesitant based on these results. Any encouragment to offer??

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....

main reason for the UDP
 

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
.

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

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

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.

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

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.

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

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

:cheers:

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

Great reading, thanks for the link

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.

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?

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

http://www.cheetahonline.com/vehicles/38pulley.jpg


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. :confused:

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

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.

SPEC, Stage 2 is recommended.

Aren't you glad I suggested this ;)

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