Got the Alta pulley but shouldn't you have a new smaller belt for it? Its all the way at the end of the tensioner now and I have heard others recommend a new belt.. Any experiences?

 

Yeah, I want to upgrade to the smaller pulley, but this belt issue has me concern. Why does the JCW kit come with the smaller belt? Can we purchase the JCW belt from Mini dealers? I think that would be the ideal setup.

Paul.

 

The majority of people DON'T use a smaller belt. I know of 2 people that have and heard their belt broke. Stick with the stock belt like the other couple hundred of us with no problems.

The JCW comes with a smaller belt? I didn't hear that...

 

You do not need a new belt with the 15% pulley. The tensioner takes up the slack, and still has room to go.

 

I enquired about that when I had my pulley installed.
According to RandyBMC, the "Pulley Master", I didn't need a smaller belt.
There is lots of swing left in the tensioner.

If you MUST HAVE a smaller belt MiniMania might sell you one.

 

>>The JCW comes with a smaller belt? I didn't hear that...

Well, my local Mini dealer said it was a bit smaller. But, he did not seem very well informed when I seeked more technical info. Since no one else claims that it`s smaller, then it probably is just the same belt. So, if it`s good enough for JCW - it`s good enough for me.

Paul.

 

No need for the smaller belt, in fact don't decrease the belt size. The 15% reduction for the pulley was developed to a) maximize the safe range rpm of the Eaton blower (up to 17,500) at working maximum engine rpms (up to 7,200). and b) avoid cavetation caused by the supercharger driven water pump.

 

MGCMAN - correction: Eaton's specified redline is 17,200rpm. With a pullied and ECU'd MCS, the supercharger spin's at a max 17,056.8rpm (7200x2.369:1)

wanted to make that clear for everyone,
Ryan

 

MGCMAN - correction: Eaton's specified redline is 17,200rpm. With a pullied and ECU'd MCS, the supercharger spin's at a max 17,056.8rpm (7200x2.369:1)

wanted to make that clear for everyone,
Ryan

Thanks Ryan. I stand corrected.

 

not a problem :smile:
With the Pulley the aftermarket-ECU 7200RPM redline is the major reason for not overspinning the supercharger. Note that MC's and stock-pulley MCS's have a modded ECU redline of 7500. I'm tenative that the stock MCS supercharger ratio is 2.069:1, but if it is, even with a redline of 7500, the supercharger is only spinning at 15,517.5rpm, well below its' redline.

In any case, the MCS belt tensioner has enough travel to accomidate the smaller pulley, with room to spare. In perspective, the supercharger pulley is so small to begin with, a 15% reduction in diameter has little overall effect for the rest of the belt drives.

Cheers,
Ryan

_________________
"Wisdom is not a function of age, but a function of experience."

 

If you are really concerned about the belt, you can bring it in to any auto parts store and they can size one up for you. Pep boys has a rack that they put your belt on and stretch it out to measure it, just ask for one measurement smaller. But you really shouldn't have to worry with that tensioner on there. JCW just includes it to keep it as close to factory spec as possible. BMW is famous for overengineering their cars, and JCW is doing the same with this kit by including the smaller belt. Do you need it? no. But it wouldn't hurt the kit, and it is always better to be on that safe side of the fence rather than the sorry side. A plus about this side is that the grass is greener too. Who would have thought it?