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Discussion Starter #1 (Edited)
My stock crank pulley is going out of balance.
What's the word with the FocusSport crank underdrive pulley.
Are they good or bad ? is a underdrive pulley good ? .or should I stick with stock
what does a harmonic balancer do and why do you i need one

here's a link to the one that i am talking about http://focus.c-f-m.com/index.asp?PageAction=VIEWPROD&ProdID=1030


thanks all
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As a general rule of thumb I wont use ANY aftermarket crank pulley unless it has a built in harmonic balancer.
 

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i would stick with oem pully.
i just took off my aftermarket because i didnt notice that much of a difference
 

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Shot me 3 deer!!!
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you won't feel a difference in power, so just stick w/ stock.
 

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C2H5OH
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Focus "Sleeper"
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^^ Agreed. Still have not seen anyone with any problems caused by an aftermarket crank pulley.
 

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Adam
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I felt a "little" more low end power.
 

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how is yours going "out" of balance?
 

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personally i liked the way this guy put it:

Originally Posted by DFv2
So, why dont aftermarket UDP manufactures make the gear with a little rubber damper...win win?

And people, its DAMPER. You can dampen, or damp. Dampener is a laymans variation of the actual term damper.

And as far as rotating assemblies go - heres some food for thought. I'll preface this by saying that I have quite a bit of experience with the physics and engineering involved with rotating assemblies, resonance, harmonics etc etc.

Facts:

1) The stock pulley is a relatively poorly balanced, heavy cast piece. If left without a bushing, it would contribute to harmful vibes at specific RPM's. This is why, and is THE reason why ford put a bushing on there. It costs less to do this than it does to CNC / mill the pulleys individually from light materials. Duh.

2) The aftermarket UDP's are essentially zero balanced and very light. They are NOT the controlling factor in the equation due to their lessened mass and excellent balance. The cannot contribute to harmful resonance in the assembly.

3) If you rotating assembly has certain resonant RPM's, the little bushing on your stock UDP is NOT going to do all that much to damp the amplitude of the vibes. Sorry. Couple kilos of high-rpm rotating mass vs. a little piece of rubber. Rotating mass is the controlling factor everytime, and by a longshot.

So, while this was fun the discussion simply isn't even fruitful. Come to your own conclusions about the UDP argument. The facts are laid out for you. In the end, however, the 1-2 HP you may or may not see just might not be worth the trouble.
 

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i also have focus central crank UDP. i cant tell that much of a difference but it does run great.

also, our cars do not have harmonic dampeners in the pulley.
I don't want to start any arguments here, but... The stock crankshaft pulley IS a harmonic/vibration dampener.
 
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