i am looking for more power with drive ability.

I could buy a 15% in the marketplace for a great price, but i don't know if 15%, 17% or 19% would be better for me.

i tried doing research but could not find much info.

my wish list is as of now

Pulley
intake
exhaust
sways
springs

 

For max HP buy the 19%. For a nice boost in HP but with a conservative approach, buy the 15%. The 17% is in between the two. I've put 15% on two of my MINIs (with zero problems) and am going with the 17% this time.

 

Whichever one you do, consider a tensioner stop. Small investment in cost and time to install, huge insurance if ever needed!!

Cheers!!

 

It all depends on what driving you do. The higher reductions (smaller pullies) allow you to easily exceed the rated redline of the supercharger. However, many many people do them without any problem.

Now, if you spend a lot of time up in the RPM range, consider what happened to GRM's MCS project car - it was dead reliable until they put a 19% pulley on it. There are theories that with a 19% pulley, the water pump will cavitate and no longer effectively pump water. Lo and behold, the GRM car blew a head gasket (overheating anyone?) shortly after adding the 19% pulley.

15% is by and large the most common choice, and there are a number of people with big hp on a 15% pulley. The only difference up top seems to be where the torque comes on. Also, IATs are already an issue on the MCS, so consider the intake air temp when you are REALLY overdriving the charger. That is why you will see a smaller pulley make more torque down low but the same hp on top.

 

Go with the 15% or 17%.The 19% will give you even more low end boost but you'll be replacing your supercharger well before the rated 100k lifespan among other potential problems.

 

Funny you mention the tension stop... I had a look under the hood today, and noticed my Detroit Tuned Tensioner Stop had broken!!!!

The SS wire had come out of the crimp at one end!

I went to my BMW workshop (not bmw, but an after market place) and had my tensioner assembly checked...It's all fine, but seems that vibrations of the past 3k have killed the tensioner stop

He thinks the DT is a waste of time, and doesn't believe crimped ends would save it under the massive tension when it does break...Something like the GTTuning design wouldn't break as it's solid metal...

Just an experience, and could be completely random manufac defect, as i know the DT has saved a couple cars...

 

really, some SCs are dying even on stock cars long before 100k.
If you think about it, the mileage life can best be described as a goal, not a real firm number. It's the number of revs at what RPM that age the SC faster... If you live at higher RPMS, the SC (all parts on the engine really) will age faster.

The best advice is to mate the pulley to what driving you do. If you do track work, I'd stick with the 15%. If you're just doing street driving and don't visit red-line that often, the larger percentages can give you some pleasure for sure!

But the M45 on our cars is a bit overdriven even stock (from the point of view of thermal efficiency). As you drive it faster and faster, the TE gets worse and worse. While many love thier 19% pulley, you'll never find one on my car.

The water pump cavitation issues has shown up from time to time. Personally, I think it has more to do with casting flash on individual water pumps than the absolute speed of the pump itself (look at a couple different pumpts and you'll see what I mean...)

There is no "best", but there is what's best for you!

Matt

 

Number One.

 

I have to say, I did a lot of research on the issue, read a lot of threads and thoughts, and had decided on 15%. then I kept reading...

For my use (mostly city and highway, rarely do I touch anything above 4.5k engine speed, and if I do its a blip) I realized the 17% would be better suited. Think about how you'll be driving it, a lot of people do 15 and then add the 2% alternator later on. I decided to save the time and just do 17 from the start, but again, I dont live in the high RPM range.

Just my 2c

edit: forgot to mention, I wound up calling ALTA and switching to the 17% before it shipped, its installed and I couldnt be happier. same cost, better power, but remember its all about how you drive and what your goals are.

 

like my previous car ( rx-8) i keep the revs very high. Lol that is why i am onlt getting 22mpg in the mini i wind the crap out of it most of the time.

so 15% would be perfect for me i think.

 

Which one would one find on your car?

 

there's a 16%. My spare SC has a 15%. All things being equal, I'll be sticking with the 15% next time I do work in that area...

I drive the car pretty conservatively now, day to day. It's almost at 100k miles and lots of parts are showing thier age. But I have no problem taking it to an extended red-line (7500) if the situation calls for it.

Matt

 

with a nod to the Doctor, 17% for sure

 

I am using 18% smaller and I don't have any problems at all.

 

Why do you feel like sticking to the 15% would be more beneficial? Are there any noticeable difference with the 1% change from 15% to 16%?

 

and even with the stock pulley, the M45 is a bit overdriven from a thermal efficiency perspective. Every bit of overdrive just gets the TEs at redline worse. But I also have other things to help with this: a GP IC, and basic water injection. Both of these help with high intake temps. I also live in CA, where the gas is pretty crappy, so the cars are pulling timing more than other places where you can get 93 octane.

I also have a ported head, and that gives a lot more low and mid range torque, so I'm not as hurting for low end pull as someone with a stock engine.

I doubt that there is a big difference between the 15% and the 16%. There's probably a small one!

Matt

 

In that case, you're spinning the SC faster than a 19% at the stock 6800 rpm limit!

 

but "red-line" on the SC isn't a hard limit. It's just a recomended range and things will age faster, and you the TE drops somewhat. I don't really care about what the exact number is, as I've already come to terms with the fact that if you push it hard, you fix it more often. Just the nature of the beast.... I'm OK with it...

Matt

 

I have a Turner Motorsports Stage 1 package on my car. 15% pulley reduction and ECU reflash. I am really happy with the kit, but the in-town gas mileage really took a hit. Makes perfect sense though, as you can hear the SC at about 2000 rpm, so boost at lower rpm = more fuel, as you can't add more air without more fuel.

 

more than anything else. Our cars have bypass valves so they are off boost if you're not pushing the car.... But then again, we do the mods so we can push the car!

Matt

 

since this thread is upon the topic...i believe it is recommended to change the belt along with the new pulley? (for all sizes) correct me if i'm wrong.

 

The company I used for the pulley install and ecu flash replaced the belt at the same time, but I don't think they used the stock belt. Lots of slap slap slap, squeek, squeek, squeek ..... They thought the noise was from the belt tensioner. Took the car to the mini dealer, they put the stock belt back on and the noise went away.

How many miles do you have on the car? I had 55K when the pulley mod was done, so if you have a fair number of miles I would recommend the belt be changed. My recommendation is to stay stock.

 

you use a stock belt on smaller pulleys, and it can slip at redline. There goes all the power you paid to get!

You're putting a smaller pulley on the car... If you don't shorten the belt, the tensioner doesn't put enough force onto the pulley. Even if you had issues with the wrong belt being a problem, put a stock belt on a 17 or 19 and it WILL slip.

Matt

 

Hi Guys - I did my pulley at home a couple of weeks ago. I bought an '02 MCS with 65,000 kms about a month ago.

For me, the 17% was the safe option as I was looking at the 19% but got a little worried...

The helix pulley came with a smaller belt which I put on. I originally routed it the wrong way and was thinking there was waaay too much slack but then I went round both idler pulleys the right way and it was happy days.

So far so good after a couple of thousand K's. Averaging about 28MPG (about 8.8l/100kms) on 98 Octane "BP Ultimate". I am in Australia.

Other mods: GP IC, Water Spray, Stainless Headers, Magnaflow cat + custom 2.5" mandrel bent system, Alta intake, fat leads. Springs and strut brace to be fitted this weekend.

NextI really need to do some ECU work... either the JCW flash or maybe the Haltech Interceptor.

Cheers,
-Pete