Underdrive Pulley Feedback Wanted - NVH and driveability - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I've been really thinking about getting an underdrive pulley, and wanted to hear some feedback from people who have it installed. I'm specifically thinking about a harmonic damper unit, because I want to give my 2.5L engine the best chance at survival I can, and the price difference isn't that much, plus it opens the door for a LWFW if I change my mind in the future (unlikely for now, but I've changed my mind many times before) The specific criteria I want to know about are ones I couldn't find through a search here or in any other forum. They're the following: 1. Does drivability improve with the A/C on? I find my car really annoying to rev-match when I turn on the A/C, as revs drop faster and take more to rise, which totally throws off my muscle memory for shifting. I imagine an underdrive pulley might make that less noticeable, which would be a great improvement for me in terms of driveability 2. Does belt whine get any quieter? My cabin sound is dominated by accessory whine with the top up. I can barely hear the engine below 3000rpm, and not at all off-throttle. Since the U/D pulley makes the accessories spin a bit slower, would it also make them a little quieter? I'm not looking for a day/night difference with either of these, just anything noticeable. A 5-10% reduction in noise is huge in NVH terms, and the same goes for drag from the A/C. Thanks for any help on this.

I have a pulley to try on an engine I'm rebuilding, but have no input for you on that yet. If you are hearing a loud whine, you may have an accessory problem. Have you tried removing the belt and running it briefly to see if the noise stops? Perhaps your PS or AC unit has a bad bearing. And I haven't a water pump, but that is a possibility as well. I don't hear any whine which drowns out the engine.

I installed the TuneRS UD pulley to my 2.5L a few years ago. I never noticed any differences between AC on or off before or after the install, but with the UD pulley I'd like to say the engine feels like it has a bit more torque available at lower rpms. However if you order one you should keep your expectations in check. Does the whine you are talking about sound like this ? If yes then more than likely it's the timing chains, especially the older roller IMS chain if I've understood correctly. For me it's the worst between 1800-2100 rpm driving at a steady speed and there's not much you can do.

I watched a you tube video the other day where the owner did a base dyno run then installed the under drive pulley completed another dyno, dyno show zero HP gains. From other reader the real benefit is for cars that get tracked, to reduce over heating of accessories ect...

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That's pretty much what it sounds like. I was hoping it was my belts (because that's what most engines sound like with the hood open), but if it's the chains, I suppose there's nothing to it other than a CRIOS mod and/or Pedro Sports Exhaust. In truth, the whine itself doesn't bother me nearly as much as the fact I can't hear the exhaust note at lower RPM. Something about the higher pitch makes it really hard for my ears to figure out what rpm the engine is at, and my around-town rev-matching suffers as a result. It's not that the car is hard to heel-toe, it's easy when I look at the tach, the muddiness of the sound is what makes it hard to do by ear. As for my expectations, it's only what I put in my original post, I'm not hoping for power gains or anything, just the well-documented lowering of PS fluid temperature and the so-far-only-hypothetical decrease in A/C pump perceived effort, plus the minor benefits of a harmonic damper.