I have read almost every post about pulleys, goods and bads for 15%-17%-19% sizes so now I think I need some final advice. First I was thinking on the 15% one, but it seems the 17% pulley will be better for me since 80% driving is between 2000 and 5000rpm, even an 19% pulley will be better, but there is a lot of belt issues so is not an option. About the SC heat.. the heat is high but if the engine rpm are lower so we have +/- the same numbers. I really never understand why BMW didn't put a small pulley with a low rev limit (6500rpm?), maybe maketing? Sure they can declare more hp at 6900rpm, but the car will be much fun if they limit to rpm at engine and put a small pulley like a lot of owners do here.

Some numbers
SC rev limit: 17200rpm
Engile rev limit: 6900? or 6950?..not sure.
Pulley size: 2.565 stock
Crank pulley: 5.48 stock

So...
SC sping is 14200rpm @6900rpm/engine with stock pulley.
With 15%, 17340rpm @6900rpm/engine.
With 17%, 17750rpm @6900rpm/engine.
And for the JCW (10.4% pulley and 7200rpm rev limiter) the rpm for the SC will be (if pulley size is correct) +/- 17169rpm, very close to the 17200rpm limit for the Eaton M45.

My question is, it is possible to down the engine rev limit to 6600rpm so I can use the 17% pulley and don't worry about the SC life? because it is obvius that with an 17% pulley the SC won't work ok after 50-60k (the SC will work, but wont generate the same boost with the time.. so at the end if the rev limiter can't be modified is better to use the 15% pulley).
The other option is to install the 17% pulley and never rev more than 6000rpm, but I don't know if it is possible do that in practice.

Any comments?

 

I think there are plenty of cars out there that run the 17% and run up to stock redline and more. I'm sure they will chime in. Another alternative is to run the M7 16%, kinda in between.

 

You're on the right track. Interesting numbers you came up with.

Short version: If you plan to track you car a lot, and run mostly near redline when you do, and you want maximum longevity, then you may want to stay with 15%. If you want best "street performance" and spend the vast majority of your time below 6000RPM, then you'll probably be happier with 17%.

I went conservative and got a 15%. Now wish I had a 17%.

 

i'm debating in between 15-17 as well.. i do a lot of street driving so i was gonna go with 17%... but reliability is my top concern.. decisions decisions

 

Same for me.. only street driving. But that is not really important.
If you take a look at the numbers even the 15% pulley can go over the supercharger rev limit, so you can do street driving or track driving it does not matter which one, the real limit is the rpm you have at engine.
At 6900rpm, with the 15% the SC will have a shorter live than stock.
The main concern is not if the SC stop working at lets say 90K after pulley install. Is the boost lost over the time that can be even lower than with stock pulley. So again if for example afert 50K we loose 1 or 2 boost lbs then we can't say the SC fail, but yes is not working at 100%. And you don't want to spend money to get more power and end with less power.

After all that, I think the only way to have long term reliability with the 17% pulley is low the engine rev limiter to at least 6600rpm (equals to 16980rpm at the supercharger), and maybe 6500 will be better. Everybody want high hp numbers at high rpm, thats good for track were every second counts, but for street will be great to have the best torque/hp ratio from 2000 to 4500/5000rpm. If you find some dyno numbers you will see that the 15% pulley does not give you too much under 4000rpm, so I don't know if for street you can feel a real improve (power feeling). But a 17% pulley, and a 2% crank pulley (if it does not give problems, which I don't know because I haven't found any info about crank pulleys) with a engine rev limit at @6300-6500rpm will give a lot more of torque/hp in the 2500-4000 range and that will be a good and reliable mod for street driving.

I just need to know if it is possible to low the rev limit (dealer or some custom ECU, but keeping the stock map), then one time you have a lower rev limiter at engine, you can go for the 17% pulley and don't worry about long term issues/boost lost. At least for me, I know I will never use the 6500-6900 range in the city, it gets too noisy and I will have to use first gear almos 80% of the time.

 

Question, I have a 06 MSC w/4500 miles, under factory warranty. If I change to a 15% after market pulley, will I void my warranty? Does JCW have a pulley that I can put on and still maintain warranty. Street driving only.

 

I think that depends on your dealer. I purchased mine from Mini of Charleston and they refused to install a 15% pulley saying they didn't approve of these "alterations".

 

Most dealers (like mine) will tell you that a reduction pulley will void the warranty on the supercharger -- in other words, it will not void your entire warranty on all components. (Best thing is probably to call your service department and ask them what their policy is.)
There is a JCW kit which includes the JCW supercharger with JCW pulley (about an 11% reduction pulley) -- which would have a warranty . . . but it's pricey.

 

Wow some interesting post's here.

luchini: Just stick with the 15 or 16% pulley. Do a search on "crank pulley". They have been proven safe. I know people that redline and track their cars regularly with 16% and 2% pullies with no problems. One guy has over 87k miles with both! If you want more power after that then go to Stage 2 mods: head, cam, turbo, something like that. One more thing, if people are worried about blowing up stuff, then don't mod your car. That is the risk with "modifing" anything. But the risk is worth the fun .

 

they said at motorwerks mini any mod i install that relates to another part will void that parts warranty, but not the full warranty completely. so yes it would probly void the sc warranty and thats all.

but i am having the same debate, dont know if i want 15 or 17%.

is 17% that much more boost or whp? just like 2psi or 5whp right?

 

Just a reality check here; You cannot rely on what a given dealer tells you about voiding the warranty. A SA may be in a good mood and tell you a pulley is fine but when you break something under the hood you could still be screwed.

Why? Because it is really not the dealer's SA who makes the call. Warranty claims are submitted to the maker by the dealer. If the Mini sees something that they don't like (a pulley for example) they won't pay the dealer for the P&L. No matter how friendly your SA is, or how much he likes you, neither he or the dealer is gonna eat the costs.

If you're into modding you have to be honest about the risks.

 

a question..

with the stock pulley you feel the SC at 4000rpm. Can someone tell me which will be the new rpm range for an 15% and for 17%?

 

+1.

 

Wow, that's tough because it's so subjective... but I feel my SC around 3200-3500rpm with a 15%... I guess I should pay more attention to when it actually starts producing measurable boost - hadn't thought about it much... I have a ScanGauge, so it's easy to watch... I'll get hard numbers tomorrow...

 

But doing this is almost like install a smaller pulley, with the 15%+2% the SC will spin at 17750rpm at 6900rpm/engine. So again you are over those 17200rpm limit.

 

Call Steve at:http://www.customminishop.com/ Like I said, he has over 80k miles with 16% & 2% pullies. Also a Cosworth head .

 

thanks for the advice, I'm making an order from them, so I will ask about the 16+2 combo

 

No prob. Steve and Brad at Custom Mini Shop will do you good .

 

they're definitely first class guys! this is my second time doing business with them and it definitely won't be the last! i just picked up my 17% and 0% pulleys today from them, including the belt, bolt, and colder plugs... (and alta lca's but that's not part of the engine). now i just need someone to install them for me in norcal

 

Just drive down here. Steve does excellent service work . Brad helps hold things up . Sorry Brad .

 

Sure you are. I'm keeping track.

 

To bring this back:
I saw a post here about someone dynoing with lots more power, but also with a 15% pulley and a 7500rpm redline. This bothers me, because even with a stock redline, the 15% pulley is overspeeding the supercharger. To me, using dynos like that is the same as the kids with hondas who blow up their cars on the dynos, and then quote the last thing the dyno could record.

So, i made a handy spreadsheet using the OPs numbers:
http://www.gstockmini.com/resources/scspeed.xls
You can change the redline value, and see if, or by how much, you're overspeeding the supercharger. It looks like the best combo is a 4% crank pulley with a JCW supercharger pulley on the stock redline, but once you go over the stock redline, not alot of combos will work.

 

I have heard that anything over 15% can over-rev the supercharger. 17% is dangerous, and you should see the disclaimers Alta has about their 19% pulleys ("Not for racing use! Can cause catastrophic failures on track! Will damage supercharger!" Etc, etc). I'm sticking with 15%, because it uses the stock belt and I don't have to drop $70 (incl. shipping) for the 17% belt from aftermarket distributors. Plus, there's the down time when you're waiting for that belt to arrive. I like going to my local supplier and getting a belt the same day. And not blowing up a $1500 supercharger.

But I'm not known for my patience or my desire for super performance.

 

so you think 17 will hurt my sc?

 

I spoke to my mini dealer about me having a 15% and any warranty issues that may occur from it. I was told that it would void the warranty on a major engine problem If they founf the pully reduction to have been the cause.
How thay could prove or dissaprove? i would hate to get into a battle over it. But hey, it is worth having . im at 44K and have an extended till 70K