Why did MINI, with all the resources and top notch engineers, decide on a 10.xx pulley (we will round to 11%)for JCW, and later for the GP cars. (I am concluding this from an earlier thread about the JCW pulley size, before that I assumed it was closer to 13%) I'm guessing due to a margin of safety and due to heat generated by a supercharger.
My real question is why there are many, maybe dozens of manufacturers of pulleys out there, and I don't know of one that offers a bolt-on pulley of less
than 15%. I haven't searched oversea tuners, so correct me if you know of any. So from stock, you have the option of JCW package or supercharger
or 15 and up. Granted, most people will still go with the 15 or 16% pulley. There are many cars out there with tons of miles logged, doing this fine. But
I have to think there are a few people outh there sitting on the fence about a pulley, that might go the way of a lesser percentage if it were an option.
An option that would make a little more power and torque, affect MPG less,
generate less heat, absolutely no question as to weather bigger injectors are needed, etc. Everyone agrees there is no reason to upgrade from a JCW to
a 15%, so wouldn't it be true the other way.
Again, I have no problems with 15,16,19, and 19% pulleys, I know they all have fans and are here to stay, I'm simply asking for more options. Any takers??? I hope I'm ready for this......Go EASY on me...

 

Is this new information on the size being ~11%? I have read that in several threads lately but it used to be that everyone quoted the size being ~14.8% .

 

14.3 to 14.8 is what I have always read, maybe the stock S is 11%. If anything under normal driving the 15% helped my mpg....

 

JCW = 10.98%

 

haha, a stock S pulley would be a 0%...that's what the percentage is based from. For example, a 15% SC pulley is 15% smaller than stock.

make sence?

 

I stand corrected.....

 

I wonder if the engineers were worried about cavitation erosion of the water pump vanes and or bearing failure of said water pump with smaller diameter (Faster turning) pullies?

 

Here's another thread that's been running lately -

It has specs for the SC, and basically, the JCW pulley % plus higher redline is very close to the "max" spec for the Eaton M45 SC... That's why the JCW is the way it is, IMO.

That said, a zillion people are betting on the SC being OK occasionally reving higher than spec... and since MINI considers the SC to only have a 100K mile life anyway and no maintenance (which we know we a good mechanic can do, regardless)...

Most people spend so little time near redline (stock or extended) that it's probably a non-issue for daily drivers. But for track cars, if your track driving style is to live in the 5000-7500RPM range, it's reasonable to interpret the M45 specs to mean you may be impacting the longevity of the SC...

I run 15%, and, knowing what I know now, I would have gone 17% based on my driving style and conditions, and felt comfortable...

 

by the way, lets pretend my supercharger failed. what kind of cost am i looking at for a replacement? or an upgrade? dont include labor, i do it myself.

 

Not much for a used one, between 4-600.

 

... if you can find one... which will likely become more difficult as the cars get older and more are failing...

New is $2163.25 at Pelican Parts.

 

owwww !!! my but just imploded .

 

Are you changing your name to "holie hind"?

 

Screw replacing that m45. Go turbo or the new kit jans working on

Jack

 

There are a lot of people spinning the 15% and as of now there doesn't seem to be a rash of supercharger failures. Anyone who tracks and or runs their car at redline all the time is going to shorten the life of the supercharger and a lot of other parts too. You got to Pay to play...

 

Read my mind.

Again, it's porbably so you stay out of the SC red zone but also so it has more flexibility in terms of what gas you can run. After all the JCW is supposed o be just as usable daily as a regular S (I am guessing).

 

JCW picked a conservative pulley upgrade because they want to be able to offer a warranty on the upgrade that will be reliable and easy to back up. Can you imagine them offering a 19% reduction pulley upgrade? How much would that cost to offer a warranty? Too much most likely.

As for wanting a milder option for pulley upgrade, the 15% is pretty tame and reliable so no real reason to think of anything more mild than that. It's fine and is bullet proof as long as you install it properly. Use your stock crank pulley.

Also none of the pulley upgrades hurt mpg, in fact some owners have reported better mpg with some pulley upgrades.

If you have paid for a JCW, why pay more for 15% pulley upgrade and void the JCW supercharger warranty. It's not just that the improvement is slight but warranty is a big concern for those who own JCW upgrades.

 

Another question might be why 15% has become the most widely used size...and the answer is pretty funny. Ask Eric at Helix.

mb

 

I too would like to know why 15% became the most common and why everyone, besides M7, made 15 their standard entry level size. I'm sure it has something to do with just having an industry wide standard setting itself for comparison purposes(our 15% pulley makes X power, vs. the other guys). What is the history of the MINI Pulley?

 

No, no. But you see the JCW goes all the way to eleven.

 

 

I think 15% became the "benchmark" because of the rpms that the sc wiull be spinning at.
If I'm correct, the stock SC spins at twice the rpms of the crank. thus, if you were to reduce that puley by 15%, you would now have to equate 15% more rpms to the sc.
My guess is that 15% at stock redline, puts the SC rpms near the max.

 

I don't want to tell Eric's story because it's his, and I'd worry about getting details wrong. Hopefully he'll chime in here... Actually, another member here was there in the beginning, too. I don't know his name, but I know he machined the first 15% pulley.

mb

 

thats the short of it - takes it to max w/out over spinning.

 

If I recall corectly that would be John (JLM on the boards) and his famed secret machine shop.