Installed the raby under-drive pulley

[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.