http://www.the370z.com/members/pokey...6-sc-speed.jpg

Red is over design speed with the stock crank pulley. Both the 88 an 84 are over

I have a 84mm pulley and ran it on a 1.0 install with no issues. Just waiting to put it on my 1.5 setup.

Interesting, so even the 88 is techically smaller than this setup should allow? I think it's the most popular pulley size though and I've never heard of a blower go out from over spinning. Thanks for that info though, cool to know how fast I'm actually spinning it

from rotrex's website the c38 has a 1:7.5 gear ratio with a max impeller speed of 90,000 now we need an accurate measurement of the O.E. pulley.

Edit: also due to the high speed nature of centrifugal superchargers the manufacturers redline is usually set a little lower than it's designed redline to CTA for warranty reasons.

the factory crank pulley is 146mm

SO an 88mm pulley would be 146/88 x 7500 x 7.5 = 93324rpm

^ So I (and everyone who runs an 88mm) am over spinning the blower by about 3k rpms? Doesn't seem to be a big deal though, you're right it can probably take a little more with no problems they just want you to stay conservative

I have found Rotrex compressor maps the show data to 120K, so someone (Rotrex) has spun the -81 that fast. I think we all be safe with some overspeed. I ran the 84mm for 10K miles and my blower did not pop.

You are only overspeed when you are turning the engine near redline. If you want to be safe, reset your max RPM to 7K with Up-Rev.