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YOUR RESEARCHAnyone using the RSS underdrive pulley?
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Install oem belt, original size
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Leading evidence: 'Install oem belt, original size' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install oem belt, original size' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I've had the pulley installed on my 996 for about two years now.
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Finally installed the RSS pulley that's been sitting around since last year.
Run rss underdrive pulley (i bypassed a/c as well)
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I'm running the RSS underdrive pulley (I bypassed A/C as well).
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I have run underdrive pulleys on both of my M96-powered cars.
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As someone else will eventually point out, the u/d pulley doesn't increase power, but it does cause less HP to be used driving the belt-driven accessories which can prevent some accessory issues when driving @ higher RPM for extended periods (i.e.
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Do the lightweight pulley's make a noticeable difference? I'm not looking for measurable power increases but a seat of the pants difference would interest me.
I have run underdrive pulleys on both of my M96-powered cars. It's the best "bolt-on" mod you can buy, in my opinion. It was one of the last mods I tried on my Boxster, after burning a good deal of money, and I ordered another one the same day I took possession of my 996.
The only downside I have noticed is that underdriving the alternator can leave the car with a less than optimal charge. This is only evident when I leave the car parked for days between trips...which isn't often. This is a minor issue of the voltmeter reading .5-1 volt low after starting, again after sitting for several days. Frequent driving and/or my battery maintainer addresses this issue.
As someone else will eventually point out, the u/d pulley doesn't increase power, but it does cause less HP to be used driving the belt-driven accessories which can prevent some accessory issues when driving @ higher RPM for extended periods (i.e. track).
There are several designs. I'd recommend using a solid pulley or one with minimal material removed rather than the skeletonized versions that remove most of the material. See p. 2 of this thread for pics:
https://rennlist.com/forums/996-foru...-pulley-2.html
One other note: Installing an underdrive pulley on the 996 is SO easy compared to the Boxster. We're talking about minutes on the 996 vs. hours on the 986.
I have also been debating on getting the U/D pulley. The main reason I have been wanting to get it is because when I turn on the A/C I can really fell the power loss from take off at stand still. I have been meaning to ask you 5CHN3LL if you can feel a difference on your car with the U/D on there.
It's not a tremendous difference. I believe the U/D pulley reduces the parasitic draw of the belt-driven accessories by 20%. It's absolutely noticeable, but not the same kind of noticeable as adding a hundred-shot of nitrous. It's a small but noticeable gain, which is all you can ask from for a mod in this price range. I feel that it revs a bit more freely.
I'm happy I did it. Twice.
The only downside is the one I mentioned earlier - my battery can wind up half volt or so low if I have only done short trips and/or let the car sit. If I'm not lazy and use the maintainer if the car's going to sit, I have no problems.
I've had the pulley installed on my 996 for about two years now.
I ordered the RSS pulley from GSR Autosport. They were back ordered so don't have it yet but will be installing it within the next few weeks. I'll post back after I have a few miles with it. Not expecting any great improvement, just subtle bump in responsiveness.
Another downside is my Boxster runs hotter if ac is off.
I think the rpms are too low to drive the water pump
If you keep the ac on, rpms are up ~150 and temp lowers
Mike
It think the theory behind the under drive pulley is to reduce the speed of spinning parts attached to the belt. Since track cars live mostly above 5k rpm. Street cars do not.
No real reason - Internet search had them high on the list, web site was easy to navigate and price was the same. After I placed the order they told me that RSS was backlogged on production so they would be out of stock for 2-3 weeks. Might not have been the case if I had gone direct but I'm not in any great rush so was willing to wait.
RSS is nice as it comes with a lock wrench. I have the Mantis so I made my own. Either way stay away from the really lightweight ones with spokes that have holes in them instead of being a solid surface as those have known to break.
The RSS version looks to be slightly larger then the rest of the pulleys on the market. They claim you can use the stock belt. I went with a 4" from Precision chassis works which came with a shorter belt, I just need to fab a tool (unless someone will lend me theirs)
Tnx FLY996
So basically the RSS pulley is about a little over an inch smaller then our original one which makes it spin at an faster RPM.
For some reason I always thought people go bigger on the U/D pulley.
Holding RPM constant, the farther the distance from the axis the higher the linear (tangential) velocity will be (re: belt speed). So an under-drive pulley which is smaller in diameter slows the belt speed down versus a stock pulley at any given pulley/engine RPM. That's as good as I can explain it so many years out of trigonometry classes.
Do you have to relieve some material from the engine case to fit this smaller pulley? I thought I read that somewhere... some owners may prefer not to modify in fear of destroying the long term appreciation expected from these future classic Porsches!
Yes, there is a small boss that sticks out from the back of the engine case. Due to the smaller diameter of the pulley it will hit this protrusion so you have to cut off a small amount.
Finally installed the RSS pulley that's been sitting around since last year.
Also installed a new oem belt, original size.
install went well, only one rookie moment....hint, car out of gear before you spin the pulley for TDC....
actually, yes... car feels more energetic right off the line, as the RPM's build it becomes less noticeable.
To soon to report on any side effects, but as with any mods fuel consumption has increased
Resurrecting old thread just wanted to share that you can get
RSS
Torque solutions for $172 after using military discount at
https://www.rallysportdirect.com/pro...lley-kit-w-a-c
go to first to verify veteran status
https://www.rallysportdirect.com/cou...iscounts-codes
copy and paste code at the last page of checkout. Won�t work in the initial check out page.
*incorrectly stated RSS*
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