986 2.5 underdrive pulley dyno graph

[Jake Raby]

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.

[Gilles]

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

.

[Cloudsurfer]

Originally Posted by Gilles

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.

[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.

[extanker]

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.

aint that the sad truth

[chaudanova]

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?

[Cloudsurfer]

Originally Posted by chaudanova

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?

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

[Gilles]

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,
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?

[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