JCW with 2% crank pulley = faster spoolup?

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Jun 21, 2007 | 08:29 AM
  #1  
Hello,

I currently have the JCW setup on my '05 MCS and have the Alta 2% crank pulley (not installed yet). Will this 2% crank pulley (effectively) spin up my supercharger as though I have a 15% - 16% supercharger pulley?
I don't want to eliminate the balancer on the OEM crank pulley if I am not going to gain anything from the 2%. However, it seems that some of the ECU flashes out there are based on a 15% supercharger pulley and that is my next, and hopefully, last engine mod.
Any input will be helpful.

Cheers, Doug.
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Jun 21, 2007 | 10:10 AM
  #2  
Edited.
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Jun 21, 2007 | 10:12 AM
  #3  
Yes, the lightened crank pulley will allow your entire engine to spool up much faster. You will also see about 1psi more boost thanks to the oversized pulley.

Side note - We know the JCW pulley is a 14.8% reduction.
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Jun 21, 2007 | 02:33 PM
  #4  
Quote: Side note - We know the JCW pulley is a 14.8% reduction.
That's been debated lately in other threads.
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Jun 21, 2007 | 06:33 PM
  #5  
I just added the 3% Alta pulley to my JCW. The car runs like a raped ape.

I love it!

I am in SM about 4 days a week. You are welcome to try it anytime you would like.

Also, I just put my crank pulley installation kit together. I have all the tools needed to do the installation.

The only tool I am missing is the belt tension tool. I used the socket on the end of the belt tensioner bolt method which actually worked pretty well!

It is definetly a noticable difference that is Killer.

The only issues I have noted so far is a vibration which feels to be under the car, only under too little throttle in first gear when leaving a stop. It feels and sounds like a part of the fender inner liner or something is vibrating. I am not entirely sure it is from this install. It could be from something else.

Jasun
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Jun 21, 2007 | 07:09 PM
  #6  
Quote: That's been debated lately in other threads.
To what avail?
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Jun 21, 2007 | 08:46 PM
  #7  
This thread here. The discussion basically starts on post 14.
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Jun 22, 2007 | 08:01 PM
  #8  
Quote: This thread here. The discussion basically starts on post 14.
A valid debate could be held regarding a range of 13.8% - 14.6% (but certainly not 10%). This is what Motoring File magazine cites:

The 200hp JCW kit came with a 13.8% reduction pulley. The 210 hp kit came with a 14.6% reduction.

Anybody thinking they can take a caliper gage to the reduction pulley and the original to measure the reduction, is kidding themselves. The effective diameter of a pulley is measured to the neutral axis of the belt, not easy to determine with a simple measuring stick.
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