under drive pulleys

There is an interesting discussion of them on Bimmerfest.com



From what little I read about them I wont add one to my 2003, I just dont think the plus outweighs the risks.



As an aircaft technician I also would never add a cold air intake, but of course im in the minority there.



Bmw gets just about all they can out of their engines, why bother adding things that for the most point are just noisemakers.



Of course your milage may and likely will vary
 
I would never use one - too much strain on secondary systems for too little gain. I'd rather bump up to a bigger turbo and stronger fuel system.
 
Cool he's from Germany. I can't wait to go there next year for spring break!

I wouldn't modify your BMW at all. It's already set up to kill.
 
Hi

Balucanb,



I have one on my E36M3, and am planning on removing it. (previous owner installed it, don't recall the brand, but its the single, smaller, crank pulley). The biggest risk imho is the crank failure issue... however I have NEVER been able to find proof of this actualy occuring... always 3rd party sources. (some quite trustworthy, but still, not solid proof). There is a paper on Dinan's web site that goes into detail on this. Also as others have said, I don't like the idea of running the water pump,alternator, etc at slower speeds than they were designed to operate.
 
I'm gonna go with sirissac here. If Dinan, a company that makes top notch performance parts for BMWs wouldn't produce a part that they could make tons of money off of, there is obviously a reason not to use it. From reading their white pages, I see that the crank pullies on BMW motors act as a harmonic damper. Removing this in favor of a lighter, smaller diameter pulley has the potential to do some damage. You probably wouldn't see it for a while, but the long term effects could be bad. And really, what is an extra supposed 5-7 horsepower going to do for you? You would be better off to go with a quality exhaust system like Supersprint, or Racing Dynamics, they are proven methods of making reliable horsepower. I have added the link to the Dinan white page about pullies below.



Dinan White Pages
 
Thanks everyone. Let me clarify. I am not changing the Crank pulley, I agree it would be a mistake. I have the pulley set from Rogue Eng. it includes 2 pulleys, 1 for the water pump and 1 for the power steering pump, I know that it might cause problems but then again anything I add aftermarket wise might. I have also heard the stories about engine damage but so far they are all legends because I can't find anyone with 1st hand knowledge about these these things causeing damage??

IndigoGTI: I have already got a Exhaust from Eisemann, but good looking out, thanks, I also have a CAI, and am re-chiping the OBD-II in a week or so. At this point "Cheap" HP is almost non-exsistant so I will take those 4-5 if I can get'em!!!!:xyxthumbs :D
 
ejant said:
Smaller pulleys mean parts are going to work harder than they were designed for resulting in premature failure.
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No, actually since the accessories will turn more slowly, they will last longer. You use bigger pulleys, not smaller when you just replace the accessory pulleys. When you use a smaller crank pulley, again, the belt driven accessories will turn at a slower rate.
 
Scottwax said:
No, actually since the accessories will turn more slowly, they will last longer. You use bigger pulleys, not smaller when you just replace the accessory pulleys. When you use a smaller crank pulley, again, the belt driven accessories will turn at a slower rate.
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Just because the pulleys turn slower doesn't mean that's a good thing - the water pump still needs to pump at the same rate. If car manufacturers could get more power safely from using larger pulleys, don't you think they'd do it from the factory?
 
Sickofitall: I really don't think it is a case of safety or doing it from the factory, The car manufactures know they could get a few more horses if they did this but the trade off is a shorter lifespan for the affected parts or a least the possibility is there, this would cost them money being a bad thing. I don't think the lifespan of the parts affected is so great that it will make a big difference, at least the bet I am making. Plus if the parts really did cause such a shortened lifespan of the affected parts I think you would hear about the problem more or the companies that sell them would either go out of biz or at least be warning the customer?
 
Balucanb said:
Sickofitall: I really don't think it is a case of safety or doing it from the factory, The car manufactures know they could get a few more horses if they did this but the trade off is a shorter lifespan for the affected parts or a least the possibility is there, this would cost them money being a bad thing. I don't think the lifespan of the parts affected is so great that it will make a big difference, at least the bet I am making. Plus if the parts really did cause such a shortened lifespan of the affected parts I think you would hear about the problem more or the companies that sell them would either go out of biz or at least be warning the customer?
Click to expand...



I was addressing Scott's statement that the parts would last longer - I fully agree that they will have a shorter lifespan :)
 
SickOfItAll said:
Just because the pulleys turn slower doesn't mean that's a good thing - the water pump still needs to pump at the same rate. If car manufacturers could get more power safely from using larger pulleys, don't you think they'd do it from the factory?
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Most factory engines don't turn fast enough that water pump cavitation is a problems. When the engine spins high enough (and many modified ones go past the original intended redline), if the water pump is spinning too fast, it will whip the coolant into a froth and the combination of air and coolant will not cool as effectively, so slowing down the impeller on the water pump will improve cooling and make it less likely the engine will throw belts.



Larger alternator and steering pump pulleys on my car made a noticable improvement in throttle response and midrange (which was weird because I expected the bulk of improvment on top end), and after 5 years, they have been trouble free. No charging problems at all either. Since the power steering and alternator not only turn more slowly, the pulleys are lighter than the stock ones, further easing any strain on the bearings of the alternator or power steering pump.



Why don't the factories use larger pulleys? Larger power steering pulleys can slightly increase steering effort, larger alternator pulleys slightly reduce battery charging at idle which can adversely affect battery life, especially since Joe Six Pack never cleans their battery cables, larger a/c pulleys may slightly reduce cooling at low engine speeds, etc. Joe Six Pack wants his engine to run as maintainance free as possible. Enthusiasts don't mind slightly higher steering effort, maintaining their charging systems at their peak and are not always as concerned about a/c performance....I took the a/c completely out of my Chevelle to reduce weight and I lived in Arizona at the time.



There are a lot of reasons the factories don't do certain things. My Accord came stock with 125 hp and not the 400-500 hp or so that I would consider adequate. The average person just doesn't care and the manufacturer will meet their expectations (and at a lower cost) instead of mine, since so few people want or care about having 400-500 hp in a family sedan.
 
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