I was originally intending on going 19%, but decided to go 15% because:

1) I like running the car to redline A LOT.
2) the 19% needs injectors to take full advantage of the reduced size of the pulley and I didn't feel like paying an additional ~$400 for injectors in addition to the $400 for the pulley and installation.
3) I got the helix so I figured I could replace the hub if I really want the extra torque in low RPMs.

To be honest, blowing a supercharger was never a big concern to me since you can get one from M7 for ~$700.

 

Should you ever damage your supercharger, you might want to consider Stiegemeir Air Flow for a ported/polished unit http://www.stiegemeier.com/index1.html , and the dealer or a salvage yard for a replacement unit. Stiegemeir works on a lot of superchargers, including the Eaton for the MCS. Good luck...

 

I am about 99% in the 19% club. I prefer a nice meaty mid-range over bouncing off the redline. Just my own preference. Even now, with the stock pulley, I typically shift by 6K, even when pushing it...did the same with my turbo miata. I think the 19% will work well with my driving style.

-jac

 

19% puts a lot of strain on the SC belt due to the small radius as the belt bends over the SC pulley.

 

The 15% is an effective part, but still very "stable". Once you get to the 19%, the strain on the engine can cause problems and the smaller size makes it very easy to shred a SC belt. Just my $.02.

-Paul

 

what about the 17% vs the 15% ?

 

15% is fine, no need for 17%. I was between 15 and 19, chose 15% and spend a little more money on other effective parts for my own peace in mind

 

i wonder what the torque/power curves look like for each of the three pulleys.....

 

The 19% can spin the SC past it's red-line, but it won't blow, it will just age faster.....

M7 sells at port and polish for $700. Not a whole SC.

I haven't seen power curves for all three (4 couning the M7 16%) pullies.

I haven't seen injectur duty cycles for all three (or four) either!

Steigemeyer does the M7 P&P. (and it costs less from S....)

Endyne does one as well. (with a slightly different philosophy).

Matt

 

yeh just became aware of steigmeyer yesterday. M7's 16% pulley looks good, but still, useless to me, cos i still don't know how the power/torque curves look for any of them.

I heard that the 19% pulley doesn't spin charger past redline with the stock engine redline. Check this out, https://www.northamericanmotoring.co...4&postcount=61

 

The post you quoted uses a 17,200 RPM redline. Someone else called Eaton, and was quoted 14,000 RPM. At 14,000 RPM, smaller pullies push the unit past redline.

But all agree that it's not a hard number. What you should look at instead, is the thermal efficiency of the unit. It's pretty flat until 10k-12k RPM, then starts to climb. The graphs on the eaton site stop at 14,000, so you can't see how bad it gets, but you start putting more power into heating the gasses, and the benefit in molecular density starts to roll off.

Matt

 

yeh i heard that the Eaton guys quote a 14,000 RPM redline to be safe i think, but i doubt its the real redline, cos the JCW's pulley is like a 14%...which would be redlining the charger easily