Has anyone gone from the JCW to a 15% pulley and made actual dyno proven gains? I'm looking for a tiny bit more daily driving torque, but don't want to sacrifice top end power that is perfect right now for me.

 

Maybe there are some known solutions out there, but pulling the JCW pulley can be tricky since the tools that are available are the correct size for the stock pulley.

 

You WILL make the power you want... as for how much more, someone will chime in and help you "with numbers". You wont loose any top end as your concern.. you WILL even get there FASTER!!

Just me..............................

Thumper

 

I have thought of this as well. However, since I now have over 65K on my car, I am going to wait until the new SC being developed by RMW is available at the end of the year. It will make the 15% pulley obsolete.

 

Although there will be more power/torque with the 15% is there going to be a significantly different over the jcw pulley? is money not better spent on other mods? interested to see how this goes as I was thinking about doing the same thing a while ago but wasnt convinced it was going to be worth the money....

 

I did it, and it is plenty worth it. I did not dyno before and after but I do have a boost gauge.
JCW 11.45% pulley = 13.5psi
Madness 15% pulley = 15psi
In peak dyno numbers this would equate to maybe 4-5HP and similar torque increases. So it does not sound like much on the surface, but more importantly than those max numbers is the shape of the curves. What you get is further movement of boost down lower in the rpm range, so you get more, and get it faster. For my JCW car, the difference was significant.

Madness hooked me with the proper pulley clamp, and then I installed my crow's foot or rather steering wheel puller to actually pull off the OEM pulley.

It was a great DIY adventure, well worth every penny and minute spent.

 

I have read that; a guy has changed their JCW pulley to 15% before and after dyno. Thus the result was ~5-6 HP.

 

Interesting - that was the sorta increases I was expecting from the change... if low/mid range is improvedthen that is really what Im after

Is it not worth just going for a 16%/17% pulley instead? More pronounced difference perhaps - any down sides to the 16%?

 

Mini 5280 recently had a Dayno Party . To find results go to Club and Reginonal forums, United States West, Mini 5280 and Look at ABOUT 15 message down and open Mini 5280 Dayno Day, 2nd message down is Old 81 posted the results. Click on Line above Mini 5280 Dayno Day and it will show all the results. 1 car was stock and the rest have been modify and the modifications are on the right colum.

 

Since the JCW is already an 11.45% reduction, I would go for the 16%. No down side other than a different size belt - which you would probably replace anyway. M7 has a good 16%er.
If I was not going to replace my SC soon, I would definately go for the 16%. Just that added low end torque is worth it.
Let us know what results you get.
OOps, almost forgot...after you change pulleys, GET IT TUNED.

 

The 15% is the recommended selection for a car that sees the track often, where it will experience prolonged hig revs. The 15% does not excessively spin the SC, cause any cavitation, and does not cause excessive heat as with higher pressured intake charges available with a higher reduction value.

For street driving, get the 16 or even the 17% and you will be happy.

Agree with for a 16% pulley!

One more thing, get the Napa/Gates 060535 belt to ensure you have no slippage if you also need a new belt. The JCW belt will also work, and I ran that belt with my 15% for over a year, but the Napa belt is just a little bit shorter and therefore tighter.

Many people just change the belt with the pullley cause you are already in there and a belt is $20.

And yes on the tune, get it to get the most out of your mods.

 

Thanks for the input guys

Quick small question (which I think I already know the answer to ) do reduced pulleys create significantly higher temps at lower revs too? I mean 'cos its a reduced pulley it will be spinning the 'charger faster at all revs when compared with the OEM pulley but is the increased heat significant??? Only reason I ask is I dont want any problems with overheating if stationary in traffic....

Cheers again and sorry to kinda highjack the thread a bit

 

You're usually only under boost above about 4000 RPM anyway. When you're sitting still or even just cruising along, the bypass valve is open and the supercharger isn't doing much (it's still turning, but it's not yielding much boost and it's not making appreciable heat).

So, no, it's a non-issue except at high RPMS.

 

ahh yes, forgot about the bypass valve - good point.

 

To be more clear on the 4K boost threshold.........
When driving in a very spirited fashion, you get boost at a much lower rpm than 4K. The smaller the pulley, the lower the boost kick-in point in terms of rpm.

This is why the JCW pulley is considered better than the standard S, and why the 15 is better than the JCW. The consensus seems to be that a pulley somewhere smaller than the 15 is where you need to be concerned of additional heat as well as excessive SC revs.

 

Thanks for the clarification, the points you have made are things that Ive considered - but thanks.


I was more concerned with heat generation at standstill but me being stupid had forgotten about the bypass valve...

 

Bump...

Any new updates???

 

I've been looking for a solution to this problem as well

 

I will be swapping my pulley here in early April. I will let you guys know the results. Not sure if they will be A/B because I will be doing a couple of other things, but I will try my best to see if I can get some in between numbers

 

Read post #6
Madness has the correct pulley tool.

 

Yes, Madness can help you out, and then you will need to get a Crow's Foot puller to attach to the Madness clamp to pull the JCW pressed pulley off.

The Crow's Foot puller is also called a Steering Wheel puller, get a decent one from Sears to do the job.

 

I have the later JCW tune , bigger IC and bigger JCW injectors, that should be good enough if ,I went to a 15% pulley?

 

You should be fine with those injectors. I know Mynes would probably recommend the 550's though.

I'm near 220whp and using the 380 injectors.

 

380'S are fine for what you have.

 

thats good but I'm really concerned about the tune as there are no shops around here in Iowa.