Hi all.

I will be getting my first MINI (BRG MCS) in June. I don't think I am going to do any mods on it right away.. but might be interested later on once I have had the car for a while.

One thing I have seen mentioned on here quite a bit is to change the pulley. Can someone please exaplain to me a little about this? I assume that the pulley is in the supercharger. But what does upgrading the pulley do exactly?

Also.. can you please tell me the pros and cons of upgrading the pulley?

Thanks!

 

The supercharger has a pulley on the side of it that is driven by the accessory belt. By having a smaller pulley the supercharger spins faster and forces more air into the combustion chamber. This creates more power.

Pros - More power

Cons - your supercharger is no longer under warranty, possible reduced supercharger lifespan, increase in underhood temps.

Do a search on "15 19" and you'll get alot of info.

 

Here's a visual aid:

 

if you have reservations don't go any smaller than 15%. it will transform the car and there really isn't any reason to go any smaller i.e 17%, 19% unless you are completely comfortable. the JCW car i believe has a 13.8% reduction pulley which may make you feel a little more comfortable with the decision.

 

but no one but JCW will sell you a 13.8% - otherwise I'd get it in a second... as it stands, I'm trying to convince myself to do a 15%

 

I'm supposed to have a 17% put in by Helix at the Dragon, but am wavering about the decision ... should I go for the 15%? I don't think I will ever race it. I would like to take driving lesons -- maybe then I'd change my mind.

 

QUOTE:
>>if you have reservations don't go any smaller than 15%. it will transform the car and there really isn't any reason to go any smaller i.e 17%, 19% unless you are completely comfortable. the JCW car i believe has a 13.8% reduction pulley which may make you feel a little more comfortable with the decision.>>

True dat, not to mention the fact that warranty aint affected if you go the JCW route to upgrade. This might explain some folks' willingness to $$PEND top dolla and get the JCWorks.

Interesting observation (I have a keen eye for the obvious ) - The popular 15% reduction is only an 8% "bump" (the % delta between 13.8 and 15) over what BMW/MINI seems to imply it's comfortable covering with its warranty.

Whereas, if you are an adventurous soul who needs to "boldly go where no warranty has gone before" and opt for the 19%, you've more than tripled your "delta" (13.8 vs. 19 is over 27% difference). Probably there's some margin of safety in the JCW kit's 13.8% size. 15% reduction is less abusive of that safety margin than 19%.

Re-reading this, it's sloppily constructed (never fear i only pen computer procedures manuals for a living), but I'm basically supporting the idea that you should be able to expect better longevity if supercharger lifespan is a concern, plus get some very nice fun performance yaya's, with the 15% pulley. For a "compromise", it seems as close to win-win as you can get.

Dealer "acceptance" of this and other mods varies with the phase of the moon, and runs the gamut from "No Way" to "No Problem". I think you're doing well to be patient since it's been said that modifying MINI's is addictive.

Tatt

_________________
Chickens go in... pies come out!

 

Someone double check my math

The # of revolutions for the same amount of belt fed over the supercharger pulley (assuming same feedrate). Pi falls out since these are all ratios.

Stock 1.000 revolutions
13.8% 1.160 revolutions (1/(1-.138))
15.0% 1.177 revolutions (1/(1-.15))
17.0% 1.205 revolutions (1/(1-.17))
19.0% 1.235 revolutions (1/(1-.19))


Now Comparing how much faster the 15/17/19 are compared to the JCW
13.8% 1.000 revolutions (1-.138)/(1-.138)
15.0% 1.014 revolutions (1-.138)/(1-.15)
17.0% 1.039 revolutions (1-.138)/(1-.17)
19.0% 1.065 revolutions (1-.138)/(1-.19)

SO:
The JCW pulley is spinning 16% faster than stock
The 15% pulley is spinning 17.7% faster than stock and 1.4% faster than the JCW pulley
The 17% pulley is spinning 20.5% faster than stock and 3.9% faster than the JCW pulley
The 19% pulley is spinning 23.5% faster than stock and 6.5% faster than the JCW pulley

 

" but no one but JCW will sell you a 13.8% - otherwise I'd get it in a second...

is there really an interest in this? If so...

 

tehre may be an interest. I'm torn between voiding my warranty and staying stock on teh pulley.

I'm pretty close to convincing myself to go 15% - but if 13.8% it would make me feel better. That said.... i may be the only person that insane.

 

You could always get a 15% and wrap a layer or two of duct tape on it - how thick is duct tape? Andy? anyone?!

 

haha... i'll end up with teh 15% since no one offers JCW style...

My neurosis will ahndle it, i suppose.

 

>>tehre may be an interest. I'm torn between voiding my warranty and staying stock on teh pulley.
>>
>>I'm pretty close to convincing myself to go 15% - but if 13.8% it would make me feel better. That said.... i may be the only person that insane.

Even if you find a 13.8% pulley and have it installed, you would still have the same warranty risk as if you did a 15. The JCW pulley is part of a complete mod package, including a new supercharger, head, exhaust, ecu upgrade, etc.

 

Yes, I am aware of that - it is a psychological barrier that one must break between installing a pulley and not.

And being able to say.. well.. MINI uses it on their own cars and gives a warranty if you buy the whole kit...

that helps those of us who are very torn..

 

Here's an interesting little snippet from the Bosch Automotive Handbook about pulleys. For a standard 6-rib DIN 7687, the effective diameter is the diameter of the pulley peaks plus 3.2 mm. This of course applies to both the drive and the driven pulleys.

 

Mmhmmm

 

It's NOT a new supercharger but let's not open up that can of worms! :smile:

 

According to this thread:

http://www.mini2.com/forum/showthrea...ght=jcw+pulley

The stock pulley measures 2.586" (65.68 mm) while the Helix/P&D "15%" measures 2.200" (55.88 mm).

That ratio is 55.88 / 65.68 = 0.8508 (or 14.92%)

If the effective diameter of the stock pulley is 65.68 + 3.2 = 68.88 mm
And the effective diameter of the 15 is 55.88 + 3.2 = 59.08 mm

Then the ratio is actually 59.08 / 68.88 = 0.8577 (or 14.23%)

 

It seems nobody can decide on the actual reduction of the JCW pulley. I've seen the following numbers:

11.6%: http://www.mini2.com/forum/showthrea...ge=2&pp=18

13.43%: http://www.mini2.com/forum/showthread.php?t=38388

13.8%: Middle of this thread

14.23%: First post of this thread

Soooooooo....which is it? :smile:

 

That is quite a dilemma. Well, "Airedale" measured stock at 2.585 (65.66 mm) and the JCW at 2.285.

Stock: 65.66 mm + 3.2 mm = 68.86 mm
JCW: 58.04 mm + 3.2 mm = 61.24 mm

61.24 / 68.86 = 0.889 or 11.1 %