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YOUR RESEARCHUpgraded idle pulleys
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Suggestion · Original poster
I think the lighter weight puts less parasitic load on the serpentine belt and the engine (when the rpm changes) so that's a good thing.
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Suggestion · Original poster
If you want to save money, you can press out and replace the bearings with the bearings of your choice.
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Suggestion
I'm pricing out replacing my idler rollers and tension pulley for my 996tt at 520$ where as you guys are out about 200$.
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Suggestion · Original poster
I've read stories ppl replacing those with Chinese $20 bearings just to find the pulleys fail in 10k miles or so...
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Even tests have been done between heavier and lighter underdrive crank pulleys on the m96 with very little to no difference.
Just to let you know that all of our 3 pulleys have been upgraded to composite material ones with the following part numbers. They are MUCH lighter..~1/2 of the stock metal ones. I just installed them and they fit fine.
http://www.autoatlanta.com/porsche-p...section=101-10
99710211700 (the one on the belt tensioner)
99710211800 (the one the alternator long bolt)
99710211900 (the lower one directly bolt onto the engine block)
1220140904c (Large).jpg
I weighed the new and old pulleys. You'll shave about 1 lb off the rear of the car for 3 pulleys
I felt my engine revs more free after....probably due to my new intake air filter though haha
I can't believe how inexpensive the 996 pulleys are. I'm pricing out replacing my idler rollers and tension pulley for my 996tt at 520$ where as you guys are out about 200$.
I think the lighter weight puts less parasitic load on the serpentine belt and the engine (when the rpm changes) so that's a good thing. Kinda like light weight flywheel makes the engine more free revving but at a much smaller scale. As long as the composite material lasts longer than the bearing itself, everything should be good.
There must be an Interchange for some of these to a generic part ? The alternator pulley is Bosch-compatible so that is a good candidate.I suspect the EBay photos are just low-res file photos so it is misleading to rely on them ?
http://www.ebay.com/itm/Porsche-987-...12532f&vxp=mtr
The tensioner -same?
http://www.ebay.com/itm/Porsche-987-...1ce327&vxp=mtr
It's very negligible in real world although it is sound reasoning in theory. Even tests have been done between heavier and lighter underdrive crank pulleys on the m96 with very little to no difference. The OEM GT3 crank pulley is lighter but mainly just to squeeze out every ounce of performance as to not leave anything left on the table.
I know of no OEM equivalent of these pulleys and yes, the eBay link ones show the same. You can get them for similar price from Porsche dealers like Sunset (
www.porschepartshub.com
) or ECStuning.
If you want to save money, you can press out and replace the bearings with the bearings of your choice. Those are std size bearings. I've read stories ppl replacing those with Chinese $20 bearings just to find the pulleys fail in 10k miles or so... However, if you choose a quality bearing with the proper spec, I don't see why they won't last as long as OE ones. However, such bearings will cost like $30~40 I think.
Agreed so I'm not claiming any hp gain
I replaced mine because mine were all very scratchy. It happens there was some confusion whether there's an updated version of these pulleys (diff sources said diff things) so I just want to confirm these are indeed designed for 996s and they fit well.
This is one of those PM's I'm actually in favor of due to a previous bad experience with a seized pulley that did a lot more collateral damage than it should've on another car.
I'm curious as to the size of the pulley in the photo. It looks identical to the pulley I just replaced in my E46 BMW which was an OEM part and cost $15 from Pelican.
The two that are not on the tensioner are 70mm in diameter and 40.5mm and 43.6mm thick including the metal spacers.
I have not measured the one on the tensioner yet.
You can take your stock pulleies to NAPA and see if they can match them up with some composite generic ones. They have a catalog with full dimensions so it's fairly easy to find a replacement one if it's a "standard design" pulley. Sort of like bearings, off the shelf ones can be found anywhere.
That's quite possible. However, you still need the right spacers, which only come with the pulley as a set. The spacers are different than the stock ones....
So I think if you want to save $$, just press out the old bearings and replace them with new ones. The stock bearings are std size bearings.
Duh, forgot the 2002 3.6L engine I bought to rebuild, has composite pulleys on it. I'll be installing them on my car in a couple weeks, with full report to follow.
Also 2 non-tensioner metal pulleys for sale when they come off my car.
Not replacing the tensioner pulley as it's a PITA & I installed a new one while I was rebuilding the engine.
Everyone has their limits within reason that suits them I suppose. I still have my radio and carpeting intact, however I do carry one of these in case I need to shed a couple pounds before a race.
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