I ran a search for this, but didn't come up with much. I obviously know what reduction pulleys do, and how they do what they do, I don't really know what the differences in the percentages equate to performance wise though.

I know WMS says that anything more than a 15% reduction pulley WILL break belts like crazy, but I had a 19% on my last car with no issues of belts breaking. Granted it was only 3 months or so... but still.

I know one the disadvantages of running too small of a pulley is going to be high heat, mitigating most of the additional air blown out, but I've never really seen any posts like this before that actually put numbers on each pulley.

It's a stretch, but it's possible that some of the people having trouble breaking 200 whp without spending 8-10k are running larger reduction pulleys .

Can anyone put any real approximate performance numbers to the various pulley sizes?

15% -
16% -
17% -
19% -

This isn't going to matter so much once the M62 upgrade comes out because most people probably won't be using a reduction pulley on the upgraded supercharger. I'm more than likely going the M62 route, but I figured I'd find out, just to be sure .

Thanks!

 

My local tuning shop is a Mini Madness dealer and I asked him the very same question yesterday. They had done a Madness Stage 4 car, just like your old one and it had a 15% on it. Just for kicks, they threw on a 19% pulley to see if it would make a difference on the dyno. He said the dyno numbers were exactly the same. He said there was more boost, but the car did not make more power...interesting to say the least.

I don't have actual numbers for ya, but just thought i'd share!

 

Wish there was more detail on the 19% pull. Things like IAT, timing and A/F ratio. If the DME pulled timing retard and dumped fuel, that would definitely show as no additional power in response to the increased boost.

 

Well I'd say thats definitely what happened. He said the excessive heat generated by it caused it to pull timing and dump fuel as you said, thus giving no gains even with the increased boost. The s/c just spins way out of its efficiency range for the smaller diameter to be effective.

 

I would imagine this would differ greatly depending on conditions. As I figured the 19% would probably generate more boost, but also produce more heat, making the additional boost pointless. (15 psi of boost at 130 degrees is the same as 18 psi of boost at 165 degrees, not scientifically accurate, but an example)

 

There's a warning on most tuning sites that says not to use the 19% for track applications as it has the tendency to overtach the SC, potentially causing premature failure. There comes a point, like with turbos that it just spins and spins and no additional air is generated, when it gets there, it's kinda pointless, as the heat generated usually mitigates any additional *slight* bump in boost.

 

I've asked about this as well without any luck, I'd like to know the difference in power between the different % pulleys.

 

Well, I dyno'd my MINI a couple weeks ago, and am waiting to install my M7 16%. I highly doubt I'll dyno it again any time soon though. Unless of course someone would like to support funds.

-Cody

 

but i wonder how the game changes when a bigger intercooler is chucked into the equation. Something like a DFIC with a 19% i'd say would make more power than a 15% with a DFIC

 

ya'll might be interested in this thread

https://www.northamericanmotoring.co...ad.php?t=22636

I've ordered a 19% from Helix to replace my 15%!

 

Here's another thread that might help you out. It originally dealt with s/c pulleys combined with cranks but it has also lots of info on percentage increases (pulley rpms's).

Good luck!

https://www.northamericanmotoring.co...ad.php?t=73952

 

the 19 may not make more power in warmer weather, but it lowers the torque curve... You get on the power sooner with a 19!

 

You should feel it during a Chicago winter!!! Whoa

 

Yes sir! 1st gear is useless in winter and i make at least 2 psig more than in the summer.

 

19% will no doubt make higher boost, but whether or not that has any affect is a factor of intake charge temp. You're bound to have a heat increase in the already teeny supercharger by pushing it further and faster outside of it's efficency range. The question becomes, is your gas good enough (Laughable in CA, gas sucks here, max of 91 octane), heat outside, and heat inside.

 

As a new MINI owner who's just starting to look into Pulley's, can someone tell me what the approx. HP gains are from a 15% pulley? Not sure if one can trust the sales promises from the manufacturer :-)

Thanks!

 

I've read 15-20hp, don't really know for sure though.