are there any other mods you must do when adding a 19% reduction pulley? I am afraid of damaging my super charger and am wondering if it is safe to run the 19% on stock injectors and ecu mapping? I may compromise with the 17% reduction but would like to get the extra power the 19% provides

 

I run a 15%, but there is nothing else that I am aware of that needs to be changed when installing 19% pulley other than a smaller belt.

 

i know but the 19% is different than the 15%

 

i have heard others say injectors, ecu mapping, and or cool plugs are required

 

Ran a 19% on my car for two years without larger injectors. However, if you regularly track your car this may not be advisable. Keep an eye on the belt and save up for injectors and a tune.
I don't think that the 19% gives any more power than a 17%, however power comes in lower and is very nice for a daily driver.

 

Colder plugs

 

HP difference between the 15% and 19% is very minor. It's the torque that you'll gain. In various other threads, the 19% spins the water pump so fast that it starts to cavitate therefore overheating the engine. It also spins so fast that it produces very high intake temperatures negating any performance over a 15%...Some run stock injectors...I wouldn't. I'd atleast upgrade to 380cc injectors. I think you'll find that a 15% pulley, 380cc injectors, and a RMW tune will make you very happy with a little more peace of mind. Just my opinion.

 

I run a 19% on the track frequently, and have monitored intake temps and coolant temps, and neither is an issue. There is more temp with a 19%, but you have the same thing with a 15% too. A good intercooler, or a water spray system is probably a good solution with any size pulley/combination of pulleys (s/c and crank)

The stock supercharger reaches its 14000 RPM limit (as per Eaton) at 6572.77 RPM stock pulley.
with a 19%, the supercharger reaches 14000 RPM at an engine speed of 5305.5 RPM. (- 4% for a 15% pulley is a difference of 5567.5-5305.5=262 RPM)
Calculations based on a stock crank pulley being 140mm & s/c being 65.5mm
I don't think cavitation is an issue over 262 rpm so...
lets take stock 6800 redline and see the difference between a 19% and a 15%.
s/c & waterpump speeds at redline with a 19% = 17943.64
s/c & waterpump speeds at redline with a 15% = 17099.24
difference = 844.40 RPM of the supercharger between a 19 and a 15. For a street car, I do not see how a 19% could hurt. Even having my car on the track many times, I have never had an issue with my water temps, and my intake temps have been hotter in traffic than they have ever been on the track (by 50F)

 

Well, I'm glad you've been able to data log these points. I'm just going off of what I've read (which has been both sides), and what I was told by Randy Webb. I had a 19% pulley in my hand, but I was talked out of it, and sold it for the 15%.

Are you running stock IC? What are you using to log this data with? I'm looking into a scangauge 2...

 

I log the temps with a custom made thermocouple/digital readout display that activates my water sprayer based upon what intake temps I set (depending on atmospheric temperature). The speeds and RPM's are just calcuations, not logged with anything. I do run a stock intercooler, but might make a custom one if I find a suitable core that fits my future needs. I have seen the intake readings on a scanguage, but do not know where they were being retrieved from. My temps are from the post intercooler manifold (that leads to the intake manifold) Theres a lot of hear-say so I like to try and provide quantitative answers when possible.

 

 

 

Go with 18%. I am OK with it.

 

been running a 19% pulley for the past 2-3 years. No issues.