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hey guys wuz up. I was checkin some website( i think it was hdk autosport and they offer an underdrive pulley. what exactly does this do and is it easy 2 install?<img src=icon_smile_question.gif border=0 align=middle>
<img src=icon_smile_big.gif border=0 align=middle><img src=icon_smile_big.gif border=0 align=middle> also which kinda rice should i pour in my fuel tank uncle ben's or minute rice?
 

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well, Unorthodox first came out with the pulleys for our cars, I will soon be dynoing these on my car, of course i have an auto, so i'm not sure on the gains for 5-speeds, I will keep you all posted on this... <img src=icon_smile_big.gif border=0 align=middle>

go here:

http://webhome.idirect.com/~trini/car/pulley.html

But for your info, there's also many discussions that will tell you why they aren't any good, but it's really all up to you, I know many that have them on their tibs and after many many miles they have had no problems that are related to the pulleys, so I don't know what to tell you...
 

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ok, i'm not a genius, but i know this answer.
do not expect hp gains that are great...a pulley doenst make horsepower, it frees up hp that is being lost through the crank. the pulley is just smaller and easier to turn, therefore needing less power to turn, freeing up some power. its hard to explain but this is what they do. lol i hope you understand, and can read my mind.lol<img src=icon_smile_big.gif border=0 align=middle>
 

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AFAIK an underdrive pully doesn't turn your alternator as fast, which frees up a little bit of horsepower used to charge your battery (through the alternator). If you do a lot of shorter drives (I think under 1/2 hour was what I read) you risk draining your battery down. Also if you have a high-power stereo you probably won't be able to drive the amps properly.

2000 Red Tiburon
1999 Blue Tiburon w/Shark Wing
 

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Here are the opinions of Steve Dinan. Anyone familar with BMW's should know the Dinan name.

The Danger of Power Pulleys &
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).

<i>Courtesy of Random</i>

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I was gonna post that Rob, the problem is that it's dealing with Beamers, Cheuk from KOREA, had an opinion regarding this same discussion with that article, and he works on tibs, if I find it I will post it...

main thing like RED and others concluded is that you might be lucky for many thousands of miles and nothing happen to your tib, but if it does, <b>it will be something major</b>... so it's a risk, yes, but I feel any mod is a new risk
 

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But I think this is a "higher risk" mod than most.

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yep, I don't fight that at all, I still need to go back thru all those posts and get more info myself, since now I have a full out system, I need to weigh the risks... <img src=icon_smile_big.gif border=0 align=middle>
 

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Discussion Starter #9
<img src=icon_smile_sad.gif border=0 align=middle>thanx 4 ur help guys. I think ill be cautious and avoid the pulley.<img src=icon_smile_dead.gif border=0 align=middle>
 

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yea yuri you need to be careful with the pulleys, you have a nice sized system in your car now and im sure you have more than one amp running it. unless you turn your system off you will definatley experience problems with charging your battery and what not. my friend has a civic w/o a system and his lights used to dim at night when he was driving for awhile.

I drive a bumble bee
 

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Rudy, sorry, but you don't know what you're talking about dude.

I have an underdrive pulley with ZERO problems. It's been on there for 1 year now, with about 20,000kms since then, and no problems, not even with my stereo.

The Tib alternator puts out 90amps, and we have a stock 600amp battery. 90 amps is a lot more than we need.

Civics put out 75amps from their alternator, and have a smaller stock battery.

I have a big stereo system with multiple amps, and constantly drive 20-30 minutes at a time only, and I've never killed the battery or even come close. The only downside to the pulley is that at red lights, with everything running, my dash looks kind of dim, but if I even rev from 800 to 1,500 rpm, everything goes back to normal.

You should have no problems with this new pulley, and my service manager doesn't mind it either.<img src=icon_smile.gif border=0 align=middle>

2000 Red Tiburon SE /w Leather
17" TSW VX-1's /w Toyo Proxes FZ4
Custom CAI, Vibrant Exhaust, Underdrive Pulley
12" Kicker Competitions, Cobalt amps, MTX powered x-over, phoenix gold cap, clarion cd
 

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But do you really know what kind of problems may be occuring on the internals of your engine. With the pullies there is that risk of messin your timing up and that could lead to a **** load of problems that you can't see. Just because there's nothing wrong now, does not mean that you engine is slowly beating itself to death! just my 2 pennies<img src=icon_smile_tongue.gif border=0 align=middle><img src=icon_smile_tongue.gif border=0 align=middle>

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<b>To everyone affected by the events of Sept 11, 2001, my best wishes go out to the men, women and families. It is some sad times indeed.</b>
 

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It runs 10% smooth so I'm not too worried.

The change is not HUGE in the pulley from stock, so I don't see it being a big problem.

The thing that scared me was the lightweight flywheel...that could potentially have WAY more problems.

And hey, let's say the pulley screws up my car, who cares? I've got another 3.5 years warranty.

2000 Red Tiburon SE /w Leather
17" TSW VX-1's /w Toyo Proxes FZ4
Custom CAI, Vibrant Exhaust, Underdrive Pulley
12" Kicker Competitions, Cobalt amps, MTX powered x-over, phoenix gold cap, clarion cd
 

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I hope you put the stock pully on when you do need to get the engine fixed under warrenty!<img src=icon_smile_big.gif border=0 align=middle>

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<b>To everyone affected by the events of Sept 11, 2001, my best wishes go out to the men, women and families. It is some sad times indeed.</b>
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Rudy, sorry, but you don't know what you're talking about dude.

I have an underdrive pulley with ZERO problems. It's been on there for 1 year now, with about 20,000kms since then, and no problems, not even with my stereo.

The Tib alternator puts out 90amps, and we have a stock 600amp battery. 90 amps is a lot more than we need.

Civics put out 75amps from their alternator, and have a smaller stock battery.

I have a big stereo system with multiple amps, and constantly drive 20-30 minutes at a time only, and I've never killed the battery or even come close. The only downside to the pulley is that at red lights, with everything running, my dash looks kind of dim, but if I even rev from 800 to 1,500 rpm, everything goes back to normal.

You should have no problems with this new pulley, and my service manager doesn't mind it either.<img src=icon_smile.gif border=0 align=middle>
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=1 id=quote>

actually i do know what i'm talking about, and you can ask anyone that knows anything about underdrive pulleys. did you even read the post that rob posted? you even stated that your lights dim at lights therefore you are experiencing problems.

I drive a bumble bee
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I hope you put the stock pully on when you do need to get the engine fixed under warrenty<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=1 id=quote>

I already stated that my service manager ok'd the pulley, so I won't have any problems there.

Rudy: I read the post from Dinan, and its apples and oranges.

He states:"removing the harmonic damper and replacing it with a lightweight alloy assembly"

On the Beta motor, the pulley is not a dampener, so this really doesn't apply.

As for the part:"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."

My battery is always at full charge when I test it, because the only time the charging cycle will be noticeably different is at idle. My lights do dim sometimes, but even before the pulley they did that when I idled and the bass hit hard. And it's only my dash light, so no big deal. I've never thrown a cel on my car, so the computer is fine. The car's temperture is identical to without the pulley, and the power steering is no harder to turn than stock.

You should really take a ride in car that has one, you'll have no complaints.

2000 Red Tiburon SE /w Leather
17" TSW VX-1's /w Toyo Proxes FZ4
Custom CAI, Vibrant Exhaust, Underdrive Pulley
12" Kicker Competitions, Cobalt amps, MTX powered x-over, phoenix gold cap, clarion cd
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Rudy: I read the post from Dinan, and its apples and oranges.

He states:"removing the harmonic damper and replacing it with a lightweight alloy assembly"

On the Beta motor, the pulley is not a dampener, so this really doesn't apply.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=1 id=quote>

Yes, the Beta motor pulley IS a dampner. It is an apples to apples comparison.

In the end, it boils down to risk. Installing a CAI is a risk, installing a pulley is a risk, hell, changing out your headlights is a risk. You should just be aware of the potentional side effects of the pulley before you purchase/install it and make an informed decision. Some people love them, some people don't want them on their motors. Personal choice.

Leave it to Random to Needlessly complicate things.
 

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Once again Random takes the cake, and shuts everyone up...or confuses them!?!?! j/k <img src=icon_smile_big.gif border=0 align=middle>

"I am not a Big Baller, I am a FAST ROLLER"
 
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