Hello All,

My appologies if this topic has been beat to death elsewhere on the forum, but I am in need of some assistance.

I am going to be adding a Supercharger pulley to my 02 MCS in the next few weeks, and need to know what others thoughts are about this modification.
I had been leaning towards the 15%, but I just took a ride in a friends 03 with a 19%, AND IT WAS INSANE QUICK!
His was not a "daily driver" though like mine, and I want to add the power without doing much else to the car. Let me explain further....... I only have the wifes approval for the pulley and install, not any other tinkering that may need to accompany the other sizes.

Can experienced pulley experts chime in please.

Thanks so much.

 

I would recommend 15% if you aren't doing anything else to the car. As you go higher up to 19%, there's more risk involve. You would also need to replace the pulley belt if you are changing to 19%.

 

15% - Most commonly used size. Reason is its very close to the JCW pulley size and is the one with the least side effects. Uses stock belt. Aprrox. 15whp increase with approx 16lb of boost.

16-17% - Very similar to 15 but requires a shorter belt. A tad more power then 15% with approx 17lb of boost

19% - Usually requires larger injectors and a ecu tune to perform at its best. Requires a shorter belt. Also is know to be harsher on the belts and they need to be changed more often. Power is about 20whp with approx. 17lb of boost.

EDIT: All of the above smaller pullies will require colder range spark plugs.

 

Thank you both for the responses.
I guess I should have mentioned the mods already in place on the car, in case that makes a difference.
-BMP intake
-Supersprint Exhaust

No other mods that should effect the engine, per say....

Again, thanks all, and keep the thoughts coming, I need the input.

 

Actually coobah having an intake and exhaust will help the pulley to work better. The intake will help feed your hungry supercharger and the exhaust will help the engine belch out more hydrocarbons.

 

Here's a good read for you to help you decide...

Randy Webb, of Webb Motorsports, describing why he only will install 15% pullies, versus the other sizes available...

http://store.webbmotorsports.com/ind...5e16c80de7b3c5

 

I'd say the 15% is the best bet.

17% & 19% get more boost, but also create more heat...
More heat = less HP gains, and higher risk of damaging something.

I've heard good comments about 19%, but I'm still really not sure about it.

 

ok all this BS about the smaller pulleys making all this heat is dumb...

and mdsbrain...your "approx" boost pressures are off...I have 17% and I am boosting 18+psi

my car moves...the 17 from the jcw pulley was a definite increase in power none of this more heat=less power....

 

I had Randy do all my work on my car so far, and have basically let him decide what I should do.....of course, with his vast amounts of knowledge...who wouldn't? I would do what Randy suggest people do.

 

oh also, the heat thing is an issue.....reading Randy's article will inform you more......I would trust someone whom went to Aeronautics school rather than a MINI forum.

Basic physics states that hot air is less dense than cold air....why a hot air balloon flies.....

More dense air means more compresion....which in turn means more power when using this air in combustion. DUH!


BTW, I am most likely the world's worst speller....so just know that.....

 

So you have had a 17 or 19 and had crappy results from it??
Because the people I kno with 17 and 19 have not had any bad results from them.
Not everything on paper is the same in the real world.
The only actual problem with 19's that I kno people have had is shredding belts, and that is because the belt is making such a sharp turn around the pulley because it is small.

Please show me REAL WORLD events/results from this "heat issue" and I will stop starting these arguements with people about this.

 

The faster you spin the rotors, the more you compress the air going through it - however, you are also increasing the heat (remember that from physics - anytime you compress you also heat). Some rotor designs minimize the effect of this, but the Roots does not. All of that means that while you are increasing pressure, at some point the heat you generate with additional compression will outweigh the pressure increase, and that point is with a 15% at about 5400RPM and higher. You also need to outweigh the fact that you are causing additional drag on the crank pulley by spinning at a higher resistance when you are forcing a higher parcel compression.

 

Randy makes a compelling argument against the 19%, but Eric @ Helix (also a veteran wrench) firmly advocates for the 19% if the injectors and mapping program are properly selected. I'll be going in this direction the first week in April and will report back before/after dyno numbers, oil temp and belt consumption. Baseline will be the dealer installed JCW set-up.

 

Off subject, sry

How did you get the auto-on fog lamps?

 

I boost over 18lbs with my 17%, TB, injectors, HAI etc etc...and I boost it all the way up to 6800..

Your not listening to what I am saying, all this scientifical talk about it "physics this and that" doesn't always come out right in real life application.

PLEASE PLEASE!!! Show me an ACTUAL person with a 19 that is not gonna blow the doors off your super conservative 15% pulley.

You can sit there and try to work it out as much as you want...but it definitly is pushing boost/not heat...IN REAL LIFE

 

well you can sit around and play it safe and be a pansy, or take the risk, get the extra horsepower and deal with it!!

 

Ian's MINI Circuit: http://gbmini.net/MINIcircuit
This is great stuff!!

 

Well, considering my car is a daily driver I wanted to go on the conservative side. Sounds like your car is track car, (lack of CAT)...or you live in like Alabama or some other red-neck state ....so wear and tear is not as much of a concern.

Also, not sure why people get their panties all in a ruffle over a forum.

Maybe your right, maybe I am right....nevertheless, for our friends case....the 15 is the best conservative way to go......aka...he is NOT building a track car.

Score one for me!

 

I think the real argument is that the relative efficiency is best with a 15%, that the increase in heat is minimal compared to the increase in pressure. The relative increase in performance begins to fall off beyone 15%, so you will get more performance with a 17% or a 19%, but not as dramatic an increase as you would expect because you get more heat along with more of that pressure.

I am 99% sure that is the Randy's argument, and others', for that matter on why 15% is the "best"... so yeah, you can go smaller if you want, and it will give you more oomph, but at a tradeoff...

So why still the 15 if you can go faster with a 17 or a 19? Because of the aforementioned belt shredding as well as overspinning of the SC. Yes, go ahead and rev it up and it's fine. But long term, you're pushing the design past what it was designed to do. So you trade off durability for performance.

And that's the argument for the 15%...

Believe it or don't believe it, but I trust the judgement of others who supposedly have analyzed this design to death. The laws of physics work, trust me...not just on paper. You just gotta be sure you're looking at the whole picture. Anyone out there with a 17 or a 19 will go faster... but for how many miles?

 

BINGO!!!!!!!!!

And tell us John, what has he won?!?!?

 

when it breaks, you fix it.

it what you do when you modify cars. people have been doing it for MANY MANY years.

 

Your supercharger is only rated for 100K miles anyway. All that happens is the bearings blow/sieze and the shaft moves out. There is a bearing replacement kit for like $100.

So lets see..if the s/c is supposed to go out at 100k.
A 15% pulley'd s/c will go out at 85K
A 17% 83K
A 19% 81K

Man, I think I see where the savings is...you can get in one more oil change before me!!

Also, with a 17% at redline 6800rpms the supercharger is at its designed redline.

 

Its not about savings...its about the difference b/tw one driver's "needs" and the next.....plus, what is best for each person's case.

 

Dude, that's fine man, replace it when it breaks. I can buy that. But like I said, that is what all the fuss about the heat is and why a 19% is still faster, but overall, that is the argument for a 15%... the efficient middle ground.

In any event, you are right, depending on how you drive, etc, one pulley is going to work better for you than another. Gotta pick what works for you.

 

And sure a 19% smokes a 15% off the line, your SC spins up faster... hang out at redline all day and the results may not be that much different. 15's, 17's and 19's all run pretty much together at the track. Just back to what exactly do you want out of it???