what is the difference between the 15%, 17%, and 19% pulleys?

 

The size.

The % revers to the size that the pully is smaller than the stock pulley. like a 17% reduction pulley is 17% smaller than the stock one. being smaller it spins up the superchager quicker and and spins the SC faster giving mre boost and more boost is more power. from what i understand changing just the pulley and belt to fit the smaller pulley gives anything from 15 - 25 hp. Colder spark pluges are also advised to prevent pinging.

I'm waiting on my 17% pulley from alta.

This is the best performance upgrade for R53 owners as far as i can tell.

 

so from what you're saying the best pulley would be the 19% one? but everyone seems to have the 15% one. why is that?

 

from what i have read so far. yes the pulley that gives the most performance gain is the 19% pulley. but spinnig the SC at such high speeds generates alot of heat. some recording tempratures of up to 350 F after the SC.

Thus for track or extended high speed use 15% will be the best, for short stints 19% gives more boost and is thus better.

I went for 17% because it is in the middle of the two just so i can tell myself it is a compromise. I'm also going to fit a IC waterspray to help with the heat problem.

 

yeah that makes sense. 15% would probably be the best choice if you're not going to be needing that much power. So thanks for your input. good luck with your 17%. im sure you'll enjoy it.

 

Thanks and no problem. good luck with yours aswell!

BTW, what model is your car? how does it look and are you going to do some other mods aswell?

 

I actually don't have one at the moment. I was supposed to pick one up today, a 2003 Liquid Yellow/ Black MCS with Black Bonnet Stripes. But it turned out that the previous owner hadn't done their paperwork and they aren't the current legal owner. so i have to wait for that to get done. So the car is completely stock. So i have a clean slate to start from. and ive been roaming this forum reading everthing i could and dont even know where to start. although the pulley seems to be the best bang for the buck.

 

You should search for supercharger reduction pulley discussion- there are roughly 6 years of discussion on this topic for the early MCS from 2003.

Basically best bang per buck upgrade is the reduction pulley for the SC.

For reliability and least hassle the 15% is safest. You can still add ECU tuning to get a bit more power to equal a 19% pulley with no specific ECU tuning. The Revolution MINI works tune is your best bet.

15% pulley does not require a smaller drive belt, generates less heat but still gives enough benefit it will be fine for most owners.

19% is also fine unless you push your car for long periods such as on the track. You can shread belts if not careful. Do routine belt changes once or twice yearly and regular belt inspections. The 19% pulley benefits from a custom ECU tune or a RMW ECU tune for 19% plus larger fuel injectors like JCW injectors for better air fuel ratio. Naturally you would benefit from good air flow so air intake and cat back exhaust upgrade that is less restrictive and high flow. Header would be OK but some will handle heat better than others.

The number of upgrades you can do to a 2003 MCS is plentiful. Plan ahead and set a budget.

More costly would be suspension upgrades-
Shocks, springs or coilovers, rear swaybar
Wheels and tires.

If you have runflats you might want to wear them out and move to non runflats. You don't have a spare so think about doing that.

The best tires- Extreme or Max Performance Summer tires even in stock sizes are like getting a suspension upgrade in terms of crisp handling and response. But summer tires are not for cold weather or any snow.

 

Good luck with that.

I only have my 2004 MCS now for 5 months and haven't modded a thing yet, still enjoying how it is, but that said the short shifter is lying next to me and of course the pulley is on the way.

I will also do IC diverter and water spray.

Rear swaybar sounds like the first and best suspention mod so that is also on the cards.

But good luck, welcome to the forum and hope to see some pics soon of your car. keep us posted.

 

minihune is wise.

Much of the thinking is that the "optimal" pulley reduction percentage depends on how/where you drive your car, and what you want out of it. In general - the smaller the pulley, the earlier in the RPM range that the car builds boost... so more torque at lower RPMS... but the less friendly it is for continuous driving at high RPMS, i.e. on the racetrack.

15% - what many, many of the most powerful cars on the track are running. At 6000-7500 RPM (with raised rev limiters due to custom tunes) for more than a few seconds, the amount of excess heat the supercharger produces negates the additional boost of smaller pulleys.

19% - what lots of folks run for max torque on the street at lower RPMS -

16-17% compromise between the two...

 

i found this link quite helpful
http://webbmotorsports.com/index.php...d=13&Itemid=31

 

Im not saying that anything Randy Webb says in that linked article is wrong--I heard it all first hand 3 years ago, but remember lots of things have changed since then (except the laws of physics unless I've been out of the loop on something really important.)
There's actually quite a bit of analysis on the Eaton blower used in our cars all about adiabatic something or other (I don't know I'm making this stuff up...) but the bottom line is you just can't keep spinning it faster, even if it never wore out or blew up, because the air temp will rise while pressure rises.
Dr Obnxs knows all this stuff, as do other very smart people on NAM. I'm out...

 

I wish some one made a 11% pulley. If and when my supercharger goes south in my 04 JCW I could obtain a cheaper OEM one and slap the 11% pulley on it and keep my stock tune.

 

It all depends on your definition of "better." If by better you mean greater capability to produce more boost, then yes. The 19% is the best. From a lot of posts I've read a 19% can OVER boost your car. The safest is 15% and is the size Mini installs on the JCW. My advice would be to research how much HP you want in the end and build a car that supports your goal. (I know...pretty lame sounding)

 

I don't think the JCW is quite 15%. Other threads have stated a noticeable difference going from a JCW to a 15% pulley.

 

It was explained to me this way. There are several things that impact the results of this discussion but if all things are equal: The smaller the pulley, the faster the supercharger spins which increases air pressure and therefore boost. However, the faster it spins you are also increasing air tempurature which degrades the boost because it is the air density which matters. Density = Pressure/Temperature. So even though the pressure is higher with a 19% pulley, the higher temperature negates the gain. Where is the best bang for the buck? Well, it's a function of RPM. A 15% pulley has offers increased density to 5500 RPM's. 19% to 3700 RPM's. So if you drive at lower RPM's you will see increased benefit to a 19% pulley.

BUT (someone's always got a big but). Changing your pulley will void your warranty, even if MINI changes it . According to Mr. Webb, when running on the track there were increased numbers of supercharger failures of a 19% reduction and even with 17%, while 15% did not fail once. Also, the amount of gain we are talking about here is very small... practically negligible. That being said there are many who have changed to 17% and 19% with no problems. It is a personal choice, and I am fine with my decision to change to 15%.

 

thanks for all the informative reply's. i think im going to go with a 15% pulley. and i just got my mini today. so im going to wait a little before i change anything on it. =)

 

and so begins another slide down the slippery slope

p.s. i would also get a smaller serpentine belt. not something you have to do, but makes slipping less likely (costs about $24).

happy trails!

 

I'm thinking of heading down this path myself. I've had my '04 MCS for 3 yrs and lately I've had the urge to mod it. I've been reading the forums and see that some people are going back to stock. Putting a stock pulley back on does not look like an option after taking it off. Does this require a complete removal of the supercharger to press the pulley on?

 

Myles2go, here is the pdf for installation:
http://www.outmotoring.com/images/ho...ulley_gen1.pdf

I did the 15% pulley. After reading all of the info and thinking about the other future mods that I would do I didn't think it would be worth any risk to do a 17 or 19 on a 5 year old car with 50K. While the risks may be debatable, I think that there is general consensus that 15% is safest for general street use based on wear and tear of the supercharger and water pump.

I didn't think of a 17 as a compromise. I actually think of the 15 as a compromise between OEM and a pulley modification. I think of 19 as a extreme for real hi performance mods.

Now I have the CAI, Pulley and standard exhaust. I have a Unichip that I am going to install until some time in the future when I can get a custom tune. Depending on how things go I will consider a catback or other exhaust.

 

Thanks! I'll be going with a 15% pulley. I've read that I should also install colder plugs at the same time.

I'd like a free flowing exhaust but I don't want to make the car louder. How many people are running the standard OEM exhaust after doing these engine mods.

 

In my humble opinion, once you do whatever mods you want, a TUNE is critical. I had done the CAI, pulley, MSD, plugs and exhaust.....It seemed quicker and more fun.....it was certainly louder (intake and exhaust, plus SC whine now) but it was NOTHING until it was tuned by Jan of RMW. If that does not get the point across....the numbers should. Stock MCS should be ~168hp. I had 176 on the first pull, post mods. By the end of the tune I am ~208hp.

My $0.02 on the exhaust, I LOVE the sound of my single side 2.5" exhaust. It is louder, but does not resonate too bad in the cab. I can easily have a conversation at 75mph, 3500rpm. Well worth the new sound!

Of course the choice is yours, but that was my experience.

 

From what I've seen, a good tune is worth the money. I put the Dinan Stage 3 software in because the local BMW dealer had it. I like the effect that had on the car and now I'm hooked to do some more.

 

hey i know this post is pretty old, im just hoping some one could help me with one problem im having with reinstalling the belt back on to the new pulley. i dont have a tensioner tool, what should i do?

 

Borrow a tensioner tool.

Sorry.

In the absence of that, in a pinch, you can put a socket on the pivot bolt of the tensioner (the one the tensioner tool pivots on), stick a small allen wrench or something similar (but hard and strong) into one of the holes that the tensioner tool engages, and use a long prybar (fulcrum on socket, one end under the allen wrench, hand on other end) to move the tensioner enough to stick another allen wrench or equivalent into the tensioner strip hole.