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2% crank pulley questions

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R53MAO View Drop Down
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    Posted: June/03/11 at 8:48pm
OK, I know this is going to open a can of worms, but ive been reading on NAM for several hours now and cant find a definitive side of the fence.  I just bought a used Alta v1 15% supercharger pulley and an m7 2% crank pulley.  They came as a package and all really wanted was the supercharger pulley, but the gains to be had with the lightweight Crank pulley are tempting.  My question is to those of you who have a lightweight crank pulley or who have had one on your car.  Have you had any signs of premature engine wear, issue of any kind after you installed the crank pulley?  If any of you still have one on your R53 how many miles have you had it on?  Thanks in advance for the information!!!  Wink
PS I will be looking to at least put on my 15% supercharger pulley sometime next moth probably, anybody planning a pulley party anytime soon?  Im sure these dont happen as often as they used to, but I figured Id ask.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 9:00pm
Not sure if anyone in the club has a single piece reduced crank pulley. I decided to stick a harmonic balancing pulley from ATI (0% size difference; they also make a slightly smaller one) out of some concerns I'd read about damage to other components (supercharger, alternator etc) of the raw torque directly hitting those components. Too scary to test it out on my car. 
If you just want the supercharger boost, it's probably safer to get that with a smaller supercharger pulley only. I have a 17% pulley. It gave me a slight but noticeable increase over 15%, which I did install first before I got the speed bug. 

I'm happy to assist with installing your pulley(s) if you can make it up this way. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote firehawk618 Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 9:02pm
IMO don't put it on.  Sell it.  Just ain't worth the minute gains you might see.
*SOLD* 05MCS, added too much to list. 193k miles
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Post Options Post Options   Thanks (0) Thanks(0)   Quote R53MAO Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 9:05pm
I've read many of the concerns about damage as well, however few seem to be substantiated. I'm leaning in the direction of not switching to the lightweight crank pulley for the same reason as you, corners, I don't want to be the one to blow up my engine! Thanks for the offer to help with my pulley install, where are you located?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnf36 Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 9:47pm
We have some people here that have them and they have not had any trouble yet. The Mini engine does not have a internal balancer like some engine. There is a reason they are called hermonic balancers and not a drive pulley. You have to ask yourself do you feel lucky. It takes time before the crank will snap. To keep this simple a mini normally runs in the 2k to 3k when you are in 6th gear this puts you in 2 places. 1 at normal posted highspeeds and 2 in the critical speed of the engine where you need that balancer.

Just my 2 cent, it is your call.

BTW the 2% will just bring on the boost alittle sooner. Better off spending the money on a cam
If everything seems under control, you're just not going fast enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 11:09pm
I'm located in Bothell (you can see the locations under our names in each post, for those of us who choose to disclose it). 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote firehawk618 Quote  Post ReplyReply Direct Link To This Post Posted: June/03/11 at 11:19pm
Make sure to put some locktite on that crank bolt.
*SOLD* 05MCS, added too much to list. 193k miles
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnf36 Quote  Post ReplyReply Direct Link To This Post Posted: June/04/11 at 12:06am
Originally posted by firehawk618 firehawk618 wrote:

Make sure to put some locktite on that crank bolt.


Second that if you go this route .
If everything seems under control, you're just not going fast enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote R53MAO Quote  Post ReplyReply Direct Link To This Post Posted: June/04/11 at 8:29am
OK, I dont think Im going to put the crank pulley on.  Ill probably just resell it on Ebay.  Both pulleys together cost me $175 shipped, so i should be able to get some of that back.  Thanks for the input everybody!
Corners, Thanks for the offer Ill send you a PM when I get back into town.  Im leaving the are for a couple weeks on Monday.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver253 Quote  Post ReplyReply Direct Link To This Post Posted: June/06/11 at 11:15pm
crank pulleys without fluid cause the vibrations onto the engine rather then the pulley. I don't remember which but it wears out a bearing somewhere due to the vibrating. I would not put that on my car. rmw and wmw both sell fluid crank pulleys that are underdriven. but they are quite pricey imo.

Gl!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote onramp Quote  Post ReplyReply Direct Link To This Post Posted: June/07/11 at 7:29am

I've had the Alta 2% lightweight crank pulley on for over nearly 50K (including lots of track miles) and no problems so far.  Doesn't mean I won't, but I did some research and find that the main engine builders are split (along the lines of who sells what, mostly), saying what John said, or saying that the bottom end of the motor is overbuilt and you don't need a damper or balancer.  Guess I'll be the test case for the club.

Alta installed the pulley, and I've had some problems with that - they forgot the spacer that comes with the pulley.  Even with the loctite, the thing kept working loose.  Called finally, and was told to install a 2MM spacer (washer) between the pulley and the bolt.  No problems since...
 
Pat
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnf36 Quote  Post ReplyReply Direct Link To This Post Posted: June/07/11 at 6:22pm
Thanks for joining in Pat, it is important to know that Pat's style of driving almost never finds him sitting at critical speed. Pat and I chatted about this for awhile before he jumped in with both feet.
If everything seems under control, you're just not going fast enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver253 Quote  Post ReplyReply Direct Link To This Post Posted: June/09/11 at 4:08pm
This was taken from innerauto.com



The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm.

Not to go away that many people have had 2% undampened crank pulleys with no issues. 

Just wanted to share the info!
03 MCS Blk/Brg Alta CAI V.2, Alta 15% V.1, One Ball, Alta SS Pos:3 , Sprint booster V.2, 17x7 Enkei, Autometer Boost Gauge, M7 Strut Brace, Tiburon Boot.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnf36 Quote  Post ReplyReply Direct Link To This Post Posted: August/08/11 at 1:04pm
I thought I would share this article I came across, couldn"t remember if we had posted it.

THE DANGERS OF POWER PULLEYS AND UNDERSTANDING THE HARMONIC DAMPER

by: Steve Dinan

I have been threatening for a long time to write a series of technical articles to educate consumers and to dispel misconceptions that exist about automotive after-market technology. Motivated by problems with customer's cars resulting from the installation of power pulleys, I wish to explain the potential dangers of these products and address the damage they cause to engines. The theory behind the power pulley is that a reduction in the speed of the accessory drive will minimize the parasitic losses that rob power from the engine. Parasitic power losses are a result of the energy that the engine uses to turn accessory components such as the alternator and water pump, instead of producing power for acceleration. In an attempt to minimize this energy loss, many companies claim to produce additional power by removing the harmonic damper and replacing it with a lightweight assembly. While a small power gain can be realized, there are a significant number of potential problems associated with this modification, some that are small and one which is particularly large and damaging! The popular method for making power pulleys on E36 engines is by removing the harmonic damper and replacing it with a lightweight alloy assembly. This is a very dangerous product because this damper is essential to the longevity of an engine. The substitution of this part often results in severe engine damage. It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics. I would first like to give a brief explanation of these principles which are critical to the proper operation of an engine. 1) Elastic Deformation Though it is common belief that large steel parts such as crankshafts are rigid and inflexible, this is not true. When a force acts on a crank it bends, flexes and twists just as a rubber band would. While this movement is often very small, it can have a significant impact on how an engine functions. 2) Natural Frequency All objects have a natural frequency that they resonate (vibrate) at when struck with a hammer. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at. This is its "natural frequency," that is dictated by the size, shape and material of the instrument. Just like a tuning fork, a crankshaft has a natural frequency that it vibrates at when struck. An important aspect of this principle is that when an object is exposed to a heavily amplified order of its own natural frequency, it will begin to resonate with increasing vigor until it vibrates itself to pieces (fatigue failure). 3) Fatigue Failure Fatigue failure is when a material, metal in this case, breaks from repeated twisting or bending. A paper clip makes a great example. Take a paper clip and flex it back and forth 90° or so. After about 10 oscillations the paper clip will break of fatigue failure. The explanation of the destructive nature of power pulleys begins with the two basic balance and vibration modes in an internal combustion engine. It is of great importance that these modes are understood as being separate and distinct. 1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine. 2) The vibration of the engine components due to their individual elastic deformations. These deformations are a result of the periodic combustion impulses that create torsional forces on the crankshaft and camshaft. These torques excite the shafts into sequential orders of vibration, and lateral oscillation. Engine vibration of this sort is counteracted by the harmonic damper and is the primary subject of this paper. Torsional Vibration (Natural Frequency) Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again. Though this back-and-forth twisting motion decays over a number of repetitions due to internal friction, the frequency of vibration remains unique to the particular crankshaft. This motion is complicated in the case of a crankshaft because the amplitude of the vibration varies along the shaft. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furthest from the flywheel or load.

Simplified Flywheel and Crankshaft Assembly
Harmonic (sine wave) Torque Curves

Each time a cylinder fires, force is translated through the piston and the connecting rod to the crankshaft pin. This force is then applied tangentially to, and causes the rotation of the crankshaft.

The sequence of forces that the crankshaft is subjected to is commonly organized into variable tangential torque curves that in turn can be resolved into either a constant mean torque curve or an infinite number of sine wave torque curves. These curves, known as harmonics, follow orders that depend on the number of complete vibrations (cylinder pulses) per revolution. Accordingly, the tangential crankshaft torque is comprised of many harmonics of varying amplitudes and frequencies. This is where the name "harmonic damper" originates.

Critical RPM's

When the crankshaft is revolving at an RPM such that the torque frequency, or one of the harmonic sine wave frequencies coincides with the natural frequency of the shaft, resonance occurs. Thus, the crankshaft RPM at which this resonance occurs is known a critical speed. A modern automobile engine will commonly pass through multiple critical speeds over the range of its possible RPM's. These speeds are categorized into either major or minor critical RPM's.

Major and Minor Critical RPM’s

Major and minor critical RPM's are different due to the fact that some harmonics assist one another in producing large vibrations, whereas other harmonics cancel each other out. Hence, the important critical RPM’s have harmonics that build on one another to amplify the torsional motion of the crankshaft. These critical RPM’s are know as the "major criticals". Conversely, the "minor criticals" exist at RPM's that tend to cancel and damp the oscillations of the crankshaft.

If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable. Major critical RPM’s are dangerous, and either must be avoided or properly damped. Additionally, smaller but still serious problems can result from an undamped crankshaft. The oscillation of the crankshaft at a major critical speed will commonly sheer the front crank pulley and the flywheel from the crankshaft. I have witnessed front pulley hub keys being sheered, flywheels coming loose, and clutch covers coming apart. These failures have often required crankshaft and/or gearbox replacement.

Harmonic Dampers

Crankshaft failure can be prevented by mounting some form of vibration damper at the front end of the crankshaft that is capable of absorbing and dissipating the majority of the vibratory energy. Once absorbed by the damper the energy is released in the form of heat, making adequate cooling a necessity. This heat dissipation was visibly essential in Tom Milner's PTG racing M3 which channeled air from the brake ducts to the harmonic damper, in order to keep the damper at optimal operating temperatures. While there are various types of torsional vibration dampers, BMW engines are primarily designed with "tuned rubber" dampers.

It is also important to note that while the large springs of a dual mass flywheel absorb some of the torsional impulses conveyed to the crankshaft, they are not harmonic dampers, and are only responsible for a small reduction in vibration.

Cut-Out View of a Tuned Rubber Harmonic Damper

In addition to the crankshaft issue, other problems can result from slowing down the accessories below their designed speeds, particularly at idle. Slowing the alternator down can result in reduced charging of the battery, dimming of the lights, and computer malfunctions. Slowing of the water pump and fan can result in warm running, while slowing of the power steering can cause stiff steering at idle and groaning noises. It is possible to implement design corrections and avoid these scenarios, but this would require additional components and/or software.

Our motto at Dinan is "Performance without sacrifice". We feel our customers expect ultra high performance along with the legendary comfort and reliability of a standard BMW.

While it is common that a Dinan BMW is the fastest BMW you can buy, performance is not our only goal. Dinan isn't just trying to make the fastest car. Instead a host of considerations go into the development of our products. Dinan puts much more effort into these other areas than does our competition.

These considerations are Performance, Reliability (Warranty), Driveability, Emissions, Value, Fit and Finish. We feel that the power pulley is a bad way to get extra power from and engine and the potential for serious engine damage is too great.

This is a simplified explanation meant to be comprehensible by those who are not automotive engineers. In trying to simplify an extremely complex topic some precision was sacrificed although we believe this explanation to be as accurate as possible. We encourage our customers to educate themselves and understand the automotive after-market because we believe that our products are the best researched, engineered, and fabricated products available.

For those interested in a more in depth and technical explanation of this topic, the reference book is Advanced Engine Technology, written by Heinz Heisler MSc,BSc,FIMI,MIRTE,MCIT. Heinz Heisler is the Head of Transportation Studies at The College of North West London. His book is distributed in this country by the SAE (Society of Automotive Engineers).

 
If everything seems under control, you're just not going fast enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SMOG Quote  Post ReplyReply Direct Link To This Post Posted: August/08/11 at 2:01pm
J:

Just a bit of lite reading????  Good Post though.

S.

I wish there was a local MINI Dealership, like our Honda, Subaru, Mazada and VW.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote johnf36 Quote  Post ReplyReply Direct Link To This Post Posted: August/08/11 at 11:51pm
S:
Just a little, Thanks.

J
If everything seems under control, you're just not going fast enough.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: August/08/11 at 11:57pm
Great reading. It is important to realize that that thing bolted to the front of the crankshaft performs two roles. 

I'm glad I got an ATI dampening pulley when my OEM harmonic balancer went bad.
If you really want to go -2%, ATI makes an undersized version - this gives you the harmonic balancing functionality and an undersized pulley. 

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