So I have done some research and I have come to the conclusion that:

15% is less power but less temps

17% more power and really only recommended with a GP intercooler, it also has a greater chance of damaging the engine/supercharger

What about the 16%? There are limited options, but is the 16% w good option, epecially if other mods and a tune are planned? Thanks

 

I have an R53 with a 15% and it now has 140,000 miles on it. It runs very good and doesn't appear to have caused any issues.

 

We offer all three sizes and anymore it's hard to say what is the most common as years ago it was always the 15%. Now with more people realizing they aren't going to ever track their car we see more go with the 16% and 17%.
I personally have a 15% pulley on my car. But really it's up to you. The smaller pulley will give you a little more grunt on the low end than the 15% but will be less efficient at the higher RPM.
Either way they will both give you more power and a huge grin

 

Just to add, I have the 15%, Cold Air Intake and a Stratmosphere Exhaust and absolutely love the car's performance. Torque and power with reliability.

 

Really the only difference between the three is the torque curve. The 17% will bring on the torque a little earlier than the 15%. Because it's only a couple psi difference between them you won't notice a big gain in power from one to the other. I went with the 17% because I knew I wouldn't be tracking the car at all. I do run it up to redline regularily and have had no issues.

 

there is also a 19%, I would only recommend that if you have an electric water pump. 17% is used a lot when you know you wont be hanging around at redline like at a track. 15% is most common

 

I have a 17%...perfect for a commuter...like said before, brings the boost on at lower rpms.
My suggestion...
If you are a track/redline junkie, and spend lots of timing running redline, get the 15%...
If you drive your car semi normal and floor it sometimes on ramps, etc, get the 17%, especially if you can get 93 octane...
If you are indecisive about everything, and wear one black sock and one brown sock just to be sure you are prepared, get the 16%!! Just kidding there....

 

and if you do track time, get a water/meth injection kit, negates all the heat created from the 17%

 

Think I am going to do the 16% and add meth/water later.

 

Unless you are going to be on a track and/or holding your RPM's up high for long periods of time....go with a 17% pulley. The boost will come in a little faster at lower rpms compared to the 15%....I think that's worth it Lots of people run 17% pulleys on a stock motor without any issues at all.