Let me know if you need help with running the SRR for the ST&E prior to the GAT.

 

exactly.

 

I took some dial calipers to 3 pulleys today.
Stock MCS Pulley: 2.565"
JCW Pulley: 2.285"
15% Pulley: 2.175"

(measurements were taken on the center rib of the pulley and represent the diameter of the surface on which the belt would have contact)

Now some basic math.
Actual reduction % of pulleys:
15%: ((2.565 - 2.175) / 2.565) * 100 = 15.2%
JCW: ((2.565 - 2.285) / 2.565) * 100 = 10.9%

 

and this is why a man with two watches never knows what time it is

https://www.northamericanmotoring.co...cw+pulley+size
refutes that but if you read here the numbers are all over the plus including MINI2 measurements

Confusing Sounds like nobody agrees.

 

Wow, I feel validated and I know my source was indeed correct about the JCW pulley!

 

Hmmm.... interesting indeed.

Any possibility that there are different pulley sizes from different production years on both stock MCS and JCW.


Just a thought.

 

I don't think there is. i know from pre 06 JCW cars that were dealer installed were getting the same supercharger installed even in 04 and prior to that. so that pulley wouldn't be different (one would think).

i know that come 05 the supercharger changed for the MCS moreso that it is similar to the JCW one with coatings in the veins of the SC. but my guess the is that the pulley is the same size.

 

Ok, so I've done some internet research and found that nobody on any continent can agree to what the JCW reduction actually is. I've seen 10.x, 11.x, 13.x, and 14.x% reductions from people that measured them compared to stock.

I guess it really doesn't matter, the JCW is a great, if not pricey, factory setup, and the aftermarket has proven 15% to be reliable.

Since the aftermarket and JCW pkgs seem to come around to about the same HP figures (meaning 15?% pulley, CAI, exhaust vs. JCW engine pkg), my only guess can be that if the JCW pulley is indeed smaller than 14.x% reduction, that the head makes up the difference.

All I know is that I have driven aftermarket cars equipped as previously mentioned and I own an 06 JCW. Though the power feels similar, the JCW seems a bit smoother. I'm sure that it comes down to tuning.

Sounds like LDG has had good luck extracting more power out of the JCW cars with it's tune, and that's a good thing!

 

This matches the measurements that I did recently.

I still speculate that there has been a change in the JCW pulley diameter at some point... otherwise some people (who I highly regard) just can't use calipers...

 

Even though I don't have a way of verifying the year of the JCW pulley my money would be on that the people measuring got it a little wrong. From a purely manufacturing and production standpoint it doesn't make too much sense to change the pulley size around. It also make less sense when you see the older threads about the pulley being around a 14% reduction and newer threads stating that the reduction is around 10%. Why would they decrease the reduction (increase the diameter)?.

Of course at this point it doesn't really matter. I used a single tool and measured 3 common pulleys. I'm sure someone else will come along later and have totally different measurements.

(just for reference the 15% I measured was a MINI Madness brand, not that it really matters as it seems like there are only 2 different manufacturers out there actually making the pulleys.)

 

Even though my measurement was recent, I think it was an *older* JCW pulley, FWIW.

I just know some of the folks who have come up with the 14.x% measurements... and know that they're pretty good at measuring and at math...

But I don't have the pulleys they measured in my hand to confirm...

 

I assume the only way to correctly measure the pulley is if it is off the car? I have an 06 JCW and am now curious as to which size it has.

 

I would love too..
I am ready to start doing some major mods to the union jackie.. but i dont want to sound stupid in the forums.. alot of the engine work people talk about are way over my head.. i dont even know where to start...
i have a MCS 06.. with no JCW.. nothing..
anyone wanna help me out with some suggestions?

 

Just for further reference. These are the pulleys I measured.

 

That picture is decieving. If those pulleys are all in the same picture and to scale, just measuring the tops of the ribs on the pictures shows that the 15% pulley is not much smaller than the JCW. The outside ribs lead the JCW to look bigger than it is: http://www.brainbashers.com/showillusion.asp?23

 

Very interesting, CmdrVimes. Maybe there are different JCW pulleys after all. I'm not able to check the size but my JCW pulley does not resemble the JCW pulley you posted. It looks spot on to the standard pulley. The sides are flat, not angled, and with the belt in place it is flush with the outer lip.

 

So, there are something different among JCW pullies after all. That might be one of the reasons why some JCWs' dyno results are different from the others.
Hmm... interesting indeed....

 

The JCW pulley that I saw - and measured to be 10.x% reduction - didn't look at all like the center one. Looks like the stock pulley, only a bit smaller...

 

The curved outer edge on the JCW pulley is because the pulley puller tool was welded to the pulley to get it off. The puller was removed by grinding the welds off. It was originally square-sided. So the belt would rest inside the area between the outer ridges (just like the stock size). The 15% doesn't have those ridges so the belt just rides on top.

The pulleys were all in one picture. They were not composited together. The original picture is here.

 

Does this mean that if it is only a 10% reduction that there is alot more head work than first thought?

 

The JCW pulley in question came off of an 05 factory JCW car. I know cause I removed it.

 

'05 Factory JCW? Didn't think those existed?

 

There were 05 build date factory JCW cars.

 

yea, i believe they were the latter 05 cars that had gotten the factory jcw.

 

....If so, and one went with a 15% and LDG tune. What kind of increase in hp would be a good guess?