I guys, I have a JCW and the other day I heard that the JCW pulley it´s not 15%. Someone wrote that the JCW pulley it´s around 11% or 12%. Is that real?. In that case, would you install a 15% pulley or would you go with the 17% pulley. I ´m afraid that could damage my car in the future (17%). Did any of you compare the JCW pulley and a 15% pulley. Thanks a lot.

Ricky.



JCW 05, Alta Intercooler, Oil catch can, Air Filter Kit, Short Shifter, GP Remap, Galfer Evolution Brakes, KW V2...

 

You won’t damage your MINI with a 17%, or 19% for that matter. The gains from the JCW 11% to an aftermarket 15% without a designated tune are very small. There is a GP map in your signature; from power output to throttle response it’s a worthwhile program for what you have. I went from the stock pulley, to 15%, to 19%, and down to the 11%; the size of the pulley is not the whole story.

 

I have heard unsubstantiated claims that the diameter of the JCW pulley is approximately a 14.5% reduction from stock.

 

14.88

 

14.881 it is that .001 that makes it JCW....

 

This is correct.

 

I’ve put the caliper to all of them, do your own measurements, get enlightened.

 

I am willing to study at the feet of a master such as yourself. Could you enlighten me? What did you determine the JCW pulley reduction(s) to be?

 

. What I don´t understand is why some people say that the JCW pulley it´s 11% and some others say it is 15%?. Why is that?. What would you recomend me?. I might get the SuperSprint Manifold soon.

 

So I'm guessing he found it to be 11%


Edit - having said that, I'd always heard it was 14.something -- though I've never measured it

 

Care to share your measurements? Not everyone has access to more than the pulley that's actually on their own car.

 

The JCW pulley is 10.9161793% smaller than the standard pulley; stock 2.565 in., JCW 2.285 in. I can imagine how the mistake has been perpetuated because I believed the 14.8% myself until I performed the measurement; that’s why I encourage each of you with an interest to be hands on and measure it. Another JCW SC myth I busted was the supposed difference in water pump drive gearing, I had a tech tell me they were taught there was a difference at the national training center, he still wouldn’t believe it wasn’t true in the face of evidence. I think the drive gear myth started with a marketing pre-release spec sheet originating in Germany, which I have a copy of, and somehow it became a “fact” after production.

Below is a photo of a JCW supercharger on the right and a standard supercharger with a 19% reduction pulley on the left. The original purpose of the photo was to illustrate the same water pump drive gear to pulley rotation ratio at 5, 10, 15, and 20 revolutions, and 20 rotation intervals up to 220. With only a glance it is evident the 19% pulley on the left is more than 4% smaller than the JCW on the right.

 

k-huevo-
So, from your ealier post, are you saying that you've experimented with different pulleys and in the end, returned to the JCW pulley?

 

Thanks for sharing k-huevo I'll definitely have to do some measuring.

I wonder if the JCW pulley is the same size on all years?

 

thats the big question

 

All the evidence I have found seems to indicate the size has remained the same. I have taken measurements of multiple JCW pulleys (factory and dealer installed) and they have all been the same. I can't seem to locate my post I made a while ago with the measurements and such, but I'm pretty sure the numbers were either identical or very close to what k-huevo posted.

*EDIT*
Just found the post It's Here.

 

I measured 2003 and 2005 JCW models; those two JCW pulleys were the same size and had the same SC water pump drive gear ratio. Later this evening I’ll measure a late build 2006 stock pulley to compare with the stock 2002 pulley I’m using for the basis, just in case there is a difference from that angle.

 

that seems like pretty interesting info since there are a buzillion threads out there stating (or assuming) that it's 14.something, as result concluding that 15% after-market pulleys are basically the same thing...

 

Have you measures any other manufacturers' reduction pulleys to see how close your measured values agree with their advertised percentages?

 

RickyJCW, from purely an economical and effort standpoint, I recommend keeping the pulley you have. As I said before, the difference in output would be small if going to a 15%.

dimini, I started with a stock size pulley, 15% second, 19% third, and am currently running a JCW supercharger.

ScottRiqui, I’ve measured Alta’s V1 model in 15% and 19% sizes and both were very close to their relative percentage.

I measured the 2006 stock pulley at 2.556 inch, so I may have inverted some numbers for the original pulley size notes or whatever (how about that tech term). This would make the JCW a 10.6025% reduction. Not enough deviation to have optimistically skewed the first result significantly.

 

Nice work K
I have been saying this since I installed one of the first round of JCW kits in early 03? ( me thinks, only a few days after its US release) and measured the pullies and water pump gearing... no one believed me then either. I had a collection of JCW pullies ranging from an early 03 right on up to the latest GP's...they are all the same size.
--Dan

 

Any particular reason you've ended up with the JCW?

 

What is the HP output of the GP map?, and where did you get it?...I have the JCW and wanted to get the GP but I was told that no even the dealership has it

 

tazio, it is a process for me, a continuum, so the JCW supercharger/pulley may not be an end, but it sure fits at the moment. My focus has always been about midrange, trying to eke out a little more from the motor for passing and drives out of corners. Along the way, I’ve seen useable performance come from improving volumetric efficiency and a suitable tune, which can match midrange gains attained via more boost (pulley reductions). The VE component is key, adding an 11% on its own won’t get you there, but having more efficient air movement will, even without reducing pulley size. An 11% will provide a moderate increase in boost and as a benefit will only moderately increase IAT. The right tune is equally important, because the driving experience (for me) is not all about raw acceleration, and I didn’t fully realize it until I lucked into the right flash. There’s no doubt, lots of boost, or increasing displacement will get you further than this conservative approach, but those paths are outside of my financial comfort zone.

 

Word. I like your style, Senor Huevo.
So which flash did you luck into?