I'm looking to get started modding my 2005 MCS and have read repeatedly that supercharger pulleys are the first step to take.

So which size do I pick? I know that the smaller the size, the larger the HP gains, but how much does the gain differ per percentage? And what's the trade off? If the smaller it is, the more it does, then what keeps people from just getting a 19%?

I guess I just need to know what each size does differently, besides horsepower differences.

Also, any suggestions on size or brand would be great!

Thank you!

Tons of threads on this if you just search. IMHO anything above a 17% will require you to deal with the additional heat that will be generated. Even a 17% on hot days can cause power loss instead of gain. 15% is a safer bet but I run a 17% and have had no problems. I live in MD, so the temperatures are a little more mild over say a place like Texas etc...

Been wanting to do this with at 15% but I live out on Siesta Key, FL (Sarasota) and the heat down here for 6 months is outrageous with high humidity. Not sure if the 15% would do much after the engine heats up and hot days. Prime example this morning at 7:45am - 80 degrees and 100% humidity. Air so thick you can cut it with a machete.

Good to know. I won't be getting a 17% then as I live in Vegas, and it's often around 110 in the summer.
Thanks for the information!

Wow. Glad there's no humidity here in Las Vegas, but there sure is plenty of heat. Thanks for the heads up.

I as well had the same issue it wasn't the question of doing a pulley kit it was what size and which one.

As the others said all my reading said that the higher you go % the more heat you will produce. And may not be proven but some speculate harsher on the motor and SC.

I opted for the Way motor 15% Kit (pulley,belt,plugs)

I called way and he asked my miles on my mini 118K at the time and instantly suggested 15%

the 15 was an instant change im talking crazy improvement and worth every penny.

mine is an everyday driver commuter with some spirited launches and back roads. hope this helps some.

the common sizes now are 15%,16%,17% and 19%

the most common is the 15%

you get more boost as you increase the reduction size of the pulley. 15% makes less boost than the 19%

but due to the effiecieny of our m45 eaton blower, at high rpms such as 6500 the blower really creates alot of heat, which will pull timining making the high boost lower power.

the 15% pulley guys ussually see the higher RPMs

where as the 19% pulley guys are using it for more low end torque, not going into high RPMs

the 19% also has another effect, it can create cavitation in the water pump, since the water pump is driven from the supercharger and therefore always spinning 19% faster

the 17% are for people who infrequently go into high RPMs

and 16% are poeple who haevnt decided wether they want the 15 or 17

high rpms being 6000+

Saltysalt - thanks for the information. Good to know. That definitely cleared up a lot for me. I appreciate the help

Well said!

I will only add to this that you can combat heat with a bigger IC (GP or maybe a GRS) as well as other kits like Meth etc... You can also avoind the water pump situation if you go electric. All of this said, if don't want to go the heavy mod route, a 15% will give you some good fun.

I am very much in the same boat right now. I am thinking of doing a 17% and a AEM WMI kit. Since I live in FL it would help with the heat and get the most out of the 17%. I wont be tuning for the WMI so I just want to maximize the 17% pulley.

That's a really good idea for compensating for the heat,. I'll have to look into that in a little while once I've addressed a few other mods and tuneups. Nice.

i run a 17% s/c pulley with a 2% crank pulley. basically similar to a 19%. rmw tuned, and then added aem w/m kit afterwards.

(many other mods too long to list right now)

about 10k miles on this setup with no issues. intake air temps are read usually 5-10 degrees F over ambient/outside.

when the w/m kit kicks on, it reads 5-10 degrees F below ambient/outside air.

this is all with frequent high rpm. never actually hitting the redline, but definitely shifting in the 5800-6200 range when driving agressively.

if you plan on getting meth, definently get the 17%, you dont need meth to run the 17%, you will have more down low with the 17% and the stock intercooler will cool down fast enough. if you were at a track every weekend all day, id say the 15%

Just my $0.02, FWIW: I live in Florida too and run a 17%. Two year ago I added a 15% pulley & DDM CAI. After running this for a year (including a full summer), I switched the pulley to a 17%. Again, another full summer with it and I think it performed pretty well despite the hellish heat & humidity.

I don't gun for the redline but frequently run amok and shift between 5K & 6K RPMs. Love my current setup and once a few other things are done I might consider water/meth or a bigger IC (GP IC).

Edit: maybe this thread should be stickied, as it has some of the best info on SC pulleys, pros & cons, and is not multiple pages in length.

Thanks for the extra information, it's appreciated. I'm pretty new the NAM, so how do you sticky a thread? If I need to do it I'd be more than happy to. I think there's some great info here

I'm pretty sure that making a sticky thread is something only a forum moderator can do. At the very least we have some really good consolidated info here.
Glad it helped you out too! The longer you stick around NAM the more you'll see that this is a common topic...

it wont be stickied. there many other threads on this subject. ive seen at least 10 in my 2 years on nam. definitely good info here and there though.

Pulleys are cheap mods to get HP for sure. However costs to fix any problems that arise (and yes some people do experience problems) for said pulley install are usually substantially higher.

Care to elaborate on this rather than simply dropping a statement? I have done numerous pulley swaps on MINIs and none have reported having problems related to the pulley. This is a proven mod that has been around for a while and I have yet to really see anyone that has had a problem because of the pulley. Poor installs yes, pulley no.

what ever happened to the guy in mexico (i think) that his buddy was running like a 29% pulley or something ridiculous?! lol. i want to know how the engine blew up :P

im also in FL, and been running a 17% for about 50k miles with NO engine issues
everything else is starting to go, but no engine or SC problems!... yet. hoping my sc will be one that lasts ridiculously long (like my brakes, over 100k on original stock setup!) always wondered, is there a 17.5% pulley, or 18%? why do the pulley sizes increment by 2's?

i also feel like there should be just one major pdf that lists all the mods you can "safely" do to the R53 based on your model, year of production, mileage, and what kind of power you want. maybe if i get bored one day ill work up a chart. only reason i mention is that its funny we still get people asking basic questions like this when all that info has been out there for so long. just getting tired of reading the same thing over and over :P now its all about the new F56, which sorry to say, its the ugliest piece of mini ive ever seen.

ill be driving my R53 into the ground; unless scion or toyota SC's or Turbos the FRS from the factory (or someone else makes a similar forced induction car).

im sure the reason why the pulleys didnt come in half sizes was due to tolerances of manufacturing.

say the pulley is 2inch diam

15% reduction would make the pulley a 1.700in
17% reduction would make the pulley 1.660in
so 17.5% : 1.650

having a +/- .005 tolerance on the diam of the pulley would allow the 17 and 17.5% be the same diameters according to the tolerance, wether or not they actually used that tolerance is besides me, i know we hold alot tigher in my shop for different applications, but a mass produced automotive product? could even be +/- .010

My experience is similar to this guy's: https://www.northamericanmotoring.co...y-and-cai.html

I went with the 15% pulley back in 2006 at 16,800 miles. Living in Arizona, it is not all that uncommon to see temperatures in the 110-120 range (minimal humidity if at all).

I've had zero issues with the car and I am hitting 97,000 miles now.

I also live in AZ and opted for the 17%. Love the down low torque and I rarely hit redline. I am however adding a water meth kit so hopefully my car stops pulling timing in the summer. Problem free so far. Make sure to go a step colder on plugs whether you go 15 or 17. Also check out euro tech in mesa. They only work on minis and jags. They know their stuff and are very fair on price.

From what I understand, they are the only place to go that is fair and who knows what the hell he is talking about. (I am in Arizona as well.)

Eurotech!