Installed the raby under-drive pulley

[Steve Tinker]

If you order the pulley from Flat6, the price includes for a new belt.
The belt supplied with mine is Gates part #KO60806. Its smaller than the original and a tight fit, but being Gates its of good quality.

As an aside, I fitted the new Flat6 pulley last week and it took me about 2.5 hours from start to finish - but that's because I used a junior hacksaw (not a dremmel)& a file to remove the exposed alloy lug. Doing it a second time I could halve the hours....

As for my experience with the upgrade, definately an improvement, noticeably in the 2,000 - 4,000 rpm where I do most of my driving. The pickup improvement from the lower revs reminds me of a car thats just had its major service - a nice, clean, linear pull.

I checked the voltage at the battery terminals and the "before and after installation" voltage difference is not worth considering above 1000 rpm.
But even more suprising is that the improved cabin noise (obviously with the roof up), its much quieter, with less engine auxilliary noise coming through the bulkhead.
Coupled with the low temperature thermostat I fitted last year, both have been well spent $$$ for me - couldn't be happier

[Jake Raby]

Glad you have had a positive experience.. About the only negative experience that can be had with this install is with ALL accessories engaged and the headlights running you can see low charge capacity only at idle. As soon as the RPM comes up even 200 RPM the situation will disappear.

[backman_z]

Jake,
Can you tell us how soon the Flat6Innovations website for ording will be up. I have been thining about puting in an underdrive pulley.

Thanks, Frans

[backman_z]

Jake,
Can you tell us how soon the Flat6Innovations website for ording will be up. I have been thining about puting in an underdrive pulley.

Thanks, Frans

[Jake Raby]

It may be down for quite some time.. we are realigning alot of the retail portion of what we do and it hasn't been going very smoothly.

[Jinster]

Does anyone have measured 0-100kph numbers before and after the install?

[Kevfra]

Question - Has anyone done a before - after test of smog emissions having changed the pulley?

Thought - Isn't one of the driven accessories an air injection pump? And where that pump does the most good is at slow RPM when it helps burn fuel more completely. If you slow the pump and pour less air - it may increase your emissions. In California these things barely pass smog when they are stock.

Am I missing something here?

[Cloudsurfer]

Originally Posted by Kevfra

Question - Has anyone done a before - after test of smog emissions having changed the pulley?

Thought - Isn't one of the driven accessories an air injection pump? And where that pump does the most good is at slow RPM when it helps burn fuel more completely. If you slow the pump and pour less air - it may increase your emissions. In California these things barely pass smog when they are stock.

Am I missing something here?

No. The air pump is electrically driven.

[Cloudsurfer]

How about providing some kind of harmonic damping on an aftermarket pulley?

[Gary H]

Originally Posted by Cloudsurfer

How about providing some kind of harmonic damping on an aftermarket pulley?

Sorry, don't understand?

[Cloudsurfer]

Originally Posted by Gary H

Sorry, don't understand?

Many engines utilize a harmonic balancer or damper, often mounted to the front of the crankshaft to quell harmonics. Porsche never did this on the M96 motors, rather utilizing the dual-mass flywheel instead. However, on the M97 motor (the 3.8 from the 997 Carrera S) Porsche did utilize a harmonic damper that is fitted behind the crank pulley. I have not yet figured if it's possible to simply fit the M97 damper, but ideally I'd love to see a damped, underdrive pulley for the M96 motors.

[Boxtaboy]

Ok, forgive my ignorance here, but when Jake says about the only negative effect is low charge capacity at idle if all the accessories are on as well as the headlights, does that mean your battery drains on you if you're stuck in traffic idling for a long time?

[Topless]

Originally Posted by Boxtaboy

Ok, forgive my ignorance here, but when Jake says about the only negative effect is low charge capacity at idle if all the accessories are on as well as the headlights, does that mean your battery drains on you if you're stuck in traffic idling for a long time?

Depends,
How big is your stereo? How big is your battery? How many hours are you idling without the occasional throttle blip?

The underdrive pulley was developed for motorsport applications to preserve the power steering pump and slow the accessories on a motor that spends a lot of it's time at high revs (4-6K). A side benefit is that it reduces parasitic drag so you get a bit more torque/hp to the rear wheels at all rpms. It is definitely possible to over think this simple device. It does not run your battery down during normal driving but it is not for everybody. If you spend long hours stuck idling in traffic with headlights on and the stereo cranked you probably don't want it. If your car spends most of it's time between 2-3k rpm, you don't want it. If your car is a weekend joyride/track toy and you use all of your rpm range, this is right up your alley.

No judgement here, just different strokes for different folks.

[Boxtaboy]

Originally Posted by Topless

Depends,
How big is your stereo? How big is your battery? How many hours are you idling without the occasional throttle blip?

The underdrive pulley was developed for motorsport applications to preserve the power steering pump and slow the accessories on a motor that spends a lot of it's time at high revs (4-6K). A side benefit is that it reduces parasitic drag so you get a bit more torque/hp to the rear wheels at all rpms. It is definitely possible to over think this simple device. It does not run your battery down during normal driving but it is not for everybody. If you spend long hours stuck idling in traffic with headlights on and the stereo cranked you probably don't want it. If your car spends most of it's time between 2-3k rpm, you don't want it. If your car is a weekend joyride/track toy and you use all of your rpm range, this is right up your alley.

No judgement here, just different strokes for different folks.

Great explanation. Thanks. I just wouldn't want to be stranded if caught in a traffic jam idling. Sounds like no way that would happen.

[Cloudsurfer]

Attached are pics of the RSS underdrive pulley with harmonic damper, designed for M97 3.8 engines. As shown, once the boss on the case has been given a haircut (like all underdrive pulleys require on these), it fits just fine once you use the longer 997 bolt.

I'm inclined to think the addition of harmonic damping is a good thing for all of these motors.

[chaudanova]

Originally Posted by Cloudsurfer

Attached are pics of the RSS underdrive pulley with harmonic damper, designed for M97 3.8 engines. As shown, once the boss on the case has been given a haircut (like all underdrive pulleys require on these), it fits just fine once you use the longer 997 bolt.

I'm inclined to think the addition of harmonic damping is a good thing for all of these motors.

Does anyone know the diameter & weight differences between the RSS unit with the harmonic damper, versus the 4" Raby/Amond unit?

[Cloudsurfer]

Originally Posted by chaudanova

Does anyone know the diameter & weight differences between the RSS unit with the harmonic damper, versus the 4" Raby/Amond unit?

Not sure of the exact weight and dimensions, but I can tell you that the damped pulley is quite heavy.