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Fanatical Member
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Discussion Starter #3
lol........I have no idea! I just sell furniture.....and used to play piano. What the heck do I know. That's why I joined this wonderful community and sent the guy the note below. :biglaugh: Doesn't make sense to me either.

"Dear topspeed-pro1-performance,

I have a SLK300. Can you tell me what kind of power gains I can expect out of this modification on my model? Do you have any Dynos from a 300 that you can share?

Thank you.


Mercedes Benz Power Pulley R171 SLK55 AMG, SLK350, SLK300 V6
Mercedes Benz Power Pulley R171 SLK55 AMG, SLK350, SLK300 V6
Item Id: 231103091102
End time: Feb-23-14 08:17:12 PST
Buyer:
100.0% Positive Feedback
Member since May-29-05 in United States
Location: CA, United States
Listing Status: This message was sent while the listing was active."
 

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Sadly Woolly has passed away
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17,375 Posts
lol........I have no idea!
The idea of changing the pulley is to change the diameter to get the supercharger spinning faster to get more boost - interesting concept on a NA engine :D

If they suggest the lack of weight gives you that much of a HP boost, then perhaps we should stop eating so many pies :D :D
 

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aka John
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13,012 Posts
This smells a *lot* like a product by AMS that claimed a lighter weight pulley resulted in more HP and torque. I'll have to see if I can dig out the thread, it generated a lot of heat and discussion over on MBWorld...
 

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Discussion Starter #7
The idea of changing the pulley is to change the diameter to get the supercharger spinning faster to get more boost - interesting concept on a NA engine :D

If they suggest the lack of weight gives you that much of a HP boost, then perhaps we should stop eating so many pies :D :D
We should stop eating so may pies!
 

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Registered
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804 Posts
Basically these things are a very bad idea:

"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 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 engines are 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:

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.


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
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.


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.​
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."

Cheers,
Brian

 

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Premium Member 2005 SLK55 AMG
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1,722 Posts
Hi all

Yea what he said

Cheers

Andy
 

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Fanatical Member
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Discussion Starter #10
And here is the response that I got from the Ebay Seller. More snake oil.

"Hi,

As stated in the description, it can give you up to 20hp and 20tq increase. That number is not guaranteed since every car is different and what modifications have been done already is different as well. We do not have a dyno sheet for that specific car.

--Will

- topspeed-pro1-performance"
 

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Administrator 2009 SLK 55 AMG/Founding member 2006
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94,173 Posts
as Paul Harvey said, and now you know the rest of the story
 

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Registered
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804 Posts
Yea what he said
The plain Engllish version:

There are two main ways these 'power pulleys' can cause trouble. Firstly, there is the chance of engine damage from removing a carefully designed integral component and replacing it with a piece of lightweight metal of questionable design and construction.

Secondly, the way these pulleys claim to extract more power is by reducing the parasitic load on the engine of various ancillary components (alternator, water pump, etc.) by a technique known as 'under driving'. Changing the diameter of the pulley causes these ancillaries to spin more slowly for each revolution of the crankshaft than they were designed to do. This runs the risk of either directly damaging these components and/or causing other components/systems to fail due to the reduced output of the ancillaries.

Cheers,
Brian
 

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Premium Member
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2,454 Posts
If Kleemann offered this modification, I might consider it if the price was right. But with this kind of engine mod, sold by a generic brand on eBay, I think it's safer to save your time and money.
 

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Fanatical Member
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Discussion Starter #14
If Kleemann offered this modification, I might consider it if the price was right. But with this kind of engine mod, sold by a generic brand on eBay, I think it's safer to save your time and money.
I don't know James......from what bac has told us, it doesn't look like a good option no matter who makes it. Therefore, Kleemann would probably never touch anything like it.

It's a good thing that we have so many people in this community that sort of "watch our backs". There are a lot of rip-offs out there.
 
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