What will a 19% Pulley do to my car and is it worth the power? I really dont want anything on my car to break. I dont take it to tracks just like to step on it every once in a while. Will a 19% pulley really do something to my car or just if i drive it hard like on tracks?

...and also. can i run a 19, 17, or 15% pulley with a stock belt? i mean whats best and safest for the car?

Hope this helps

Safest would be the 15%. Remember, the water pump is connected to the end of the supercharger. Over spinning that pump can't be too good in the long run. From stock, the 15% feels really powerful. Besides, if you never drive a MINI with a 17 or 19%, then you wouldn't know the difference over the 15%. I believe the JCW MINI has a 14% pulley, so from an engineering standpoint they are close and the 15% shouldn't hurt the engine at all since it's so similar to a stock set up. BMW wouldn't put something on a car that wasn't supposed to last, would they?

I've had a 15% pulley for 3 years, and got a 19% 3 months ago.

The difference is impressive. It's not about a lot more HP, but more about available power. With the 19%, I get enough power from the low RPM range. I never go above 6kRPM.

It really depends on your driving style and needs. Personally, I wanted more low-end punch and am pleased with the 19%.

FWIW, I have a 19% pulley and say to just go with a 15% pulley. Mixed results but lately the 15% has been proven to make more power up top than the 19%. I may be switching down sometime...

EDIT: ^^ What he said ^^ I'm not afraid to rev my car up to redline when I need to. I'm more about top end than low end, with that said re-read the above lol

I've driven a 15% and a 19% (mine being a 19%) and I vote 19. More fun, more low end punch. It won't hurt anything.

Safest... Don't Touch it.

Best bang for the Buck .. 15%.

Next two are for the power Hungry.. 17% and 19%.. Difference is there in the begining but thats about it unless you update the Intercooler it doesn't last. since it can't keep up with the extra heat.

Add the 2% crank. again unless on the track where every .001 counts. Doesn't make a difference in the experience for everyday driving.

If interested.. I have an 03 for 2 days it was Stock. then 15% for 1 year, 17% for 2 months, 19% for 1 year and finially 19%+ 2% for 1 year 10months and still going. As for the belt it lasted 1 year 7 months. with the 19% same belt was used when i added the 2% crank. so i will be changing the belt once a year.

Oct 2002 - Dec 2003 - stock pulley - 33K miles
Dec 2003 - May 2003 - 15%
May 2003 - today - 19% - I'll hit 101K miles tomorrow

I change the belt each spring before the autocross season really gets cranked up. Never had a belt break.

Lots of street use obviously, plus autocrossing about every 2 weeks from late February until early November. On the street, I don't drive very aggressivly most of the time so rpm ranges between 2000 and 4500rpm. I'll take it up over 6000 a couple of times a week typically, though occasionally I'll get on a roll.

On course at an autocross, I'll use every last rpm all the way up to 7300. Shifting is determined by the course, but if the fast way is to bounce of the rev limiter for a second or two I don't hesitate to do so.

Assuming you warm the oil up before driving hard, engine wear is largely based on duty cycle. Based on the driving described above, the vast majority of my engine hours are spent below 3500rpm. I could go back to a 15% pulley, shift a little later or drive a few mph faster on the way to work and end up putting the exact same wear and tear on the water pump (and thus the whole cooling system) and supercharger.

If you spend a LOT of time at high rpm, the 15% is probably the better route.

Scott
90SM

I know the 15% is safe, I have about 107,000 miles on my 15% with no problems as of yet. I have thought about swithcing it out to a 17 or something, but just havent yet. Maybe on the next supercharger

Nik

My 02 have 90,000 miles and I track it about 15+ days a year. I put it on 60,000 miles ago. I have never had a problem and love it. Which one you get you will enjoy.

Motor on

I have heard from a performance shop that 19% is reaching the capacity of the Supercharger and can generate excessive heat. Of course what happens depends the weather and how hard you are driving.

I did a 15% and a 2% and have seen very good results. The 2% increases bottom end and being much lighter the car is more responsive. I didn't change the alternator pulley as these are auto sensing alternators and they can deal with a 2% speed increase.

You won't over spin the water pump as it is only spinning faster for the given engine RPM and will still be spinning within its range unless you hit redline, in which case it will be spinning 19% over what it would before but within its tolerance.

i spend most my time in the lower rpm range. never go to the track or anything. so what im understanding from you guys is that the higher the percentage, the more responsive in lower rpm's? i was gonna go with the 15% just for safety reasons but will i still feel the difference to the stock pulley nicely?

You will feel a difference, but if you're spending most of your times in the lower RPM, I'd recommend the 19%. I initially got the 15% and within 5000 miles, I moved up to the 19%. Save yourself the money and hassle of installing a different pulley, go for the 19%. I recently decided to change my belt and after 20000 miles, my belt looked fine, no stretching, no fraying, nothing, sort of made me want to put it back on and get another 20k out of it.

For street driving where you're not bumping up against the rev limiter all the time, I doubt there is much difference between the 15% and 19% in terms of stress level on the SC or water pump. The 19% is turning these only ~4.9% faster than the 15%. Where the 19% does start to push the limits, in my opinion, is the belt tensioner and possibly A/F ratios in an otherwise stock car. I have the short Gatorback belt with the 19%, and the tensioner is extended to where there is only about 1/4" or less of the indicator strip sticking out. If I could find a belt that was 1/2" shorter, I'd use it. No signs of belt slip or abnormal wear, but it just seems to me to be at the limit. For the A/F ratio, Helix posted some results showing the 19% on a stock engine gets into the 13-14 range at times. Again, probably OK for normal street driving but about at the safe limit.

That said, the extra low-end grunt from the 19% makes it much more fun than the 15%! I had a 15% for about 1 year before moving to the 19%, and I'd never go back. With some low cost upgrades to the stock IC and scoop to handle the extra heat + the JCW injectors, you have a very nice package. But if you're ONLY going to do the pulley and NOTHING ELSE, and not fuss over changing the belt every 15K mi, then stay with the 15% ..... Ha Ha Ha ... if you can .... once you start modding it takes enormous will power to say "enough".

JCW = 14.7%

I think temps across engine rpm in the IC need to be considered so A/F ratios can be adjusted. But apparently, efficiency drops way off after 17%. The JCW pulley has no problems all day long at the track...1,000 - 1,200 miles of track work last season and it keeps on ticking.