Just curious,
Has anyone that has switched from a 6lb to an 8lb pulley dynoed the results? I have a friend who has an 8lb pulley and his truck only makes 5rwhp more than mine. This is on the same dyno, with the same outside temp. However he does have 10-15 ft/lb more torque. I have also run both trucks at the track, and they are virtually identical.

In addition, if I remember correctly, Trucking magazine did an article on L blower upgrades and I think they mentioned that they only noticed minimal gains by increasing boost levels by 2 pounds--12 pounds to 14.

I've been debating on the 8lb lower, but I'm not sure if the extra pressure on the motor is justified.

 

If you can find that mag pick it up, there's some good stuff in that issue.

I don't remember the #s from their test. If someone doesn't post them I will tomorrow. If I recall the lower pulley made a difference while the upper didn't do all that much.

 

the blower discharge temperature increases as the blower spins faster so power gains begin to fall of at a certain level. The screw type blower can make more boost with less heat. I'm going to install a 50HP NOS system to help with the roots blower high boost discharge temp problem, -123F NOS is an effective way to cool down the intake charge. I will have it done next month.

 

Been wondering about this question myself.
I've got that "Truckin'" article back at the house, so I can't quote it from here, but they did conclude that you could really push this Eaton supercharger and get some serious HP/torque out of it; but if you really want to take it up a notch (you race at the track, etc.) you've got to bolt on the more efficient supercharger (screw type).

I think I'm going to just move up to the 6 lb lower along with the JL Diablo chip and air intake. Then I'll probably see how big a deal it is to get the L upper pulley installed. I don't really ever see myself running this thing at the track so I'm not sure I'd ever realize the return on the hefty investment for the screw type s/c. Although I am the first one to say "bigger, better, faster, more" when it comes to gadgets and car stuff... But gawd, three to four grand?!? That could put an awful lot of chrome and performance into my bikes...