Adding more supercharger boost used to be relatively simple--just add a 15%, 17% or 19% smaller supercharger pulley.

Ahh, but now we also have the choice of adding a crank pulley, with several choices there too. There's the lightened crank pulley with stock diameter and the lightened crank pulley that is 2% larger than stock (supposedly it works like this: let's say you already have a 15% smaller supercharger pulley installed, well this 2% larger crank pulley makes your 15% SC pulley perform like a 17%). And as if that weren't enough, there is now a 3% larger crank pulley, effectively making your SC pulley an 18%.

If I've lost you, check out this page: http://www.altaminiperformance.com/p...ankpulley.html

So, now that we're presented with all these choices, let me ask some of you tuning pros out there: what is the best way to go here? I have no pulley(s) yet, but will be getting some or one pretty soon. Should I just stay with a tried-and-true 15% SC pulley?

For my situation, I want more power, but reliability--my MINI is my daily driver too. So would I be tinkering too much by adding a crank pulley? Is a 17% SC pulley better than having a 15% SC pulley and a 2% crank pulley?

Sorry for all the questions, but this is a confusing issue, with all these choices? :smile:

 

I was going to purchase the 15% reduction pulley but I have heard about the 17%. In terms of HP has any one measured(dynoed)? I am concerned with reliability as well. Do they have electric fans for cooling so you don't have to worry about over heating?

I am newbie and I am sure there are articles out there at this moment. I guess a search is in progress

 

Okay, let's say you have a 19% reduced supercharger pulley AND a 3% overdriven crank pulley--

19%
+ 3%
22%

Effectiveley a 22% pulley! Would you just expode your engine? Why not just throw a grenade down throttle body! What do you think?

 

I know of a couple people running a 19% with a 2% = 21% with no problems at all even driven on the track. I wouldnt go as far as to call it a grenade.

I am personally running a 15% with a 3% =18% and its a great combo all around.

 

What are the boost numbers those with >19% are seeing? Any special temp mods, especially for the tracked car, like water/alc inj? Any friends running a 19+4=23%?

 

It shouldn't be long until someone tries it. A few weeks back there was a long thread on just this topic. Alta continues to encourage someone to give it a shot.

 

All these things MULTIPLY, not add (but the difference is small). So for a crank pully oversize of x% and an underdrive pully of y%, the total speed increase of the SC is

Speed Increase = 1 - (1+x)*(1+y). This equals X+Y+XY. So, for a 19% and a 3%, you end up with is 22.57% Not a bid deal, but the math is so easy, there's no excuse to do it wrong.

Things to look for....
Fuel injector duty cycle. If that hits 100%, any more air just leans the mixture. Not good.

Fuel trims. This tells you if the fuel map you're using is any good.

Air Intake Temps. If these get too high, you loose efficiency.

SC Red-line. Going much more aggressive than 15% means the SC can run faster than rated RPM when the Mini is at it's upper RPM range.

Matt

 

The Dr. is correct about the very slight difference in adding them up. In the interests of KIS we have always stated the 19%+3%=22%. The actual calulated difference is so small that is doesn't really matter. Since the different size crank pulleys are starting to become popular, this method is something we were trying to adopt to make easy comparo from one setup to another.

Early next week look out for our dyno graphs of a 19% car vs. a 23% car. We will disclose the boost had by the 23%, and using the 17K redline of the SC as an Engine redline we will be calculating the area under the curve. This will show how which setup is better. Either less boost over a wider RPM, or more boost over a shorter RPM.

Air temps won't be any different because the SC will be spinning the same speed at either redline. Should be fun to prove one way or the other!

 

"kisS" I'm always covered by that last S.

 

I was thinking the same thing.... but I think Jeff was trying to be diplomatic with us

 

Three cheers for you guys

This is exactly the kind of testing we need to evaluate performance alternatives. Keep up the good work

 

Do we have any 3% lightened crank pulley vs. 0% Lightened Crank Pulley results out there ? That is with a 15% pulley

I saw the resulta of the 19% plus 3% = NOT GOOD

Onasled ????

 

A 15% reduction pulley seems to be reliable since thats similar to the JCW setup. If you go with a 17 - 19 pulley you are spinning the SC faster which will cause more wear due to higher rpms. That doesnt mean you can't get a good service life from it. The faster you rev something , the quicker it wear out is the general rule. You also are putting more stress on engine parts by running more boost. You will also hit a point in which you don't really create any more power because the IC can't cool the intake charge enough and you will be wearing out parts for no reason.
Thats why most go with a 15, intake, exhaust... it gives you a good bump in power and seems to be reliable.