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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Thu, Dec-01-2011, 09:31:23 PM   #1
fritzdegner
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Default Underdrive Power Pulleys

I'm doing some belt/pulley maintenance and started looking at the the power pulley kit from Turner. For those with this kit or other power pulley kits, do they provide any noticeable power? Any downside or problems with them?

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Old Thu, Dec-01-2011, 10:21:37 PM   #2
EmDeeAr
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Default Re: Underdrive Power Pulleys

I was going to do this mod, but decided against it for financial reasons. If I had the money on tap, I would purchase them. Power pulleys are sometimes regarded as the best bang for your buck, especially if you can install them yourself.

I would go with either Rogue Engineering or UUC. These kits only under-drive the power steering and water pumps. Turner's kit (if I'm not mistaken) under-drives three things: the power steering pump, the water pump, and the alternator. I would avoid under-driving the alternator because it can cause problems with the electrical systems of the car (radio - especially if you have the HK system, lights in the cabin, etc.) There is no concrete proof of this, but I'd just stay away from it anyway.

Here is everything that I've learned about under-drive pulleys. It was a lot of searching and flip-flopping back and forth on whether or not to go through with it, so this should save you some time and help you make a decision.

-They don't provide power, but rather release "hidden" power, or power lost due to parasitic drag on the engine.
-Power gains are pretty minimal. If you drive an M3 with under drive pulleys, a CAI, an exhaust, and a tune, it will likely pull harder than a stock M3. However, power pulleys aren't noticeable by themselves. It's not that a CAI and a tune and stuff make the pulleys more efficient, but rather that all that power adds up to something noticeable (5hp+2hp+10hp, etc. = noticeable).
-No power pulley kits that I've seen under-drive the crank. There might be some out there. Whatever you do, DO NOT under drive the crank. Some have done this without issues, but, nevertheless, it can mess up the harmonic balancing of the engine. If you under-drive the crank and use a lightened flywheel, the engine and/or drivetrain (not really sure which is affected) will be doomed.
-No problems with under-driving the power steering pump, at least that I know of. I've read that it makes the steering feel even better!
-I don't think under-driving the water pump will be an issue. Admittedly, the cooling systems in these cars is quite weak, but it won't be affected that much. If you have upgraded to the Stewart water pump, then you will be fine, without a doubt. Some people do the front fan delete in conjunction with the water pump pulley. I wouldn't do this, even if you do have the Stewart pump.

-Michael

Last edited by EmDeeAr; Thu, Dec-01-2011 at 10:25:48 PM.
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Old Thu, Dec-01-2011, 11:30:45 PM   #3
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Default Re: Underdrive Power Pulleys

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Originally Posted by EmDeeAr View Post
I would avoid under-driving the alternator because it can cause problems with the electrical systems of the car (radio - especially if you have the HK system, lights in the cabin, etc.) There is no concrete proof of this, but I'd just stay away from it anyway.
Sorry, but this is inaccurate. With a stock audio system and a charging system in good condition there will be no issues at all with the alternator UD pulley (I think it is only like 20%). If you are running an aftermarket audio system with extra amps or if your charging system is not in good condition (battery and/or alt not working 100%) then the UD pulley would be a bad idea. I have known several people with the alt UD pulley and they have had no issues of any kind.

That having been said personally I would rather have the alternator rather than the water pump pulley unless I was running a Stewart pump. They flow better and the ~20% UD will likely even out to about OEM pump flow.
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Old Thu, Dec-01-2011, 11:32:49 PM   #4
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Default

Waste of money. Save the close to $200 you will spend on pulleys (to net about 2hp) and spend it instead on about 5 autocross events, or a track day. Either will be much better "bang for the buck."
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Old Thu, Dec-01-2011, 11:33:34 PM   #5
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Default Re: Underdrive Power Pulleys

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Waste of money. Save the close to $200 you will spend on pulleys (to net about 2hp) and spend it instead on about 5 autocross events, or a track day. Either will be much better "bang for the buck."
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Old Thu, Dec-01-2011, 11:34:16 PM   #6
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Default Re: Underdrive Power Pulleys

Hm ok so my mistake on the alternator thing. I think all my other info is accurate.

Then go for it for sure if you don't mind spending the money!
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Old Thu, Dec-01-2011, 11:39:18 PM   #7
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Default Re: Underdrive Power Pulleys

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Hm ok so my mistake on the alternator thing. I think all my other info is accurate.

Then go for it for sure if you don't mind spending the money!
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Old Fri, Dec-02-2011, 02:47:10 PM   #8
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Default Re: Underdrive Power Pulleys

This may be wrong as well but I have heard for some reason on our cars you NEVER are supposed to under drive the crank pulley? No idea why but I have heard its no bueno...
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Old Fri, Dec-02-2011, 03:46:51 PM   #9
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Default Re: Underdrive Power Pulleys

Crank pulley is the harmonic ballancer. Remove that is really hard on cranks.
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Old Fri, Dec-02-2011, 05:32:54 PM   #10
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Default Re: Underdrive Power Pulleys

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Originally Posted by boomersooner523 View Post
This may be wrong as well but I have heard for some reason on our cars you NEVER are supposed to under drive the crank pulley? No idea why but I have heard its no bueno...
Yeah it's not good at all. I don't know the exact mechanics of it, but it messes up the harmonic balance of the engine. In my searches, I read of some people that did it w/o problems, but I still think it's treading in murky waters. Now if you under-drive the crank AND use a lightweight flywheel, the engine is really not going to be happy....
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Discussing Underdrive Power Pulleys in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)