MPI pulley sizing vs blower speed vs PSI

[347strokin]

I found a post once that contained the pulley sizing vs blower speeds vs PSI.
I can't seem to find it now.

I am wondering if I can run a 27 top and a 24 bottom on a Stage 2 Apex?

I chatted briefly with someone at MPI and he said it was okay but I just want to make sure I'm not under spinning the blower causing low oiling problems.

27 top and 24 bottom will get me around 10 lbs? Is this correct.

Thanks in advance.

 

[347strokin]

Originally posted by HAMMER

On the Stage-II

Rotrex 30-64/74 the maximum compressor speed is 120,000 rpm

(A) The 30-64/74s are internally overdriven 9.49:1 (Cannot be changed)
(B) 26/22 pulleys is a 1.181:1 ratio (Can be changed with pulleys)
(C) Engine Rpm (Can be changed with clutching/gearing)

Example: (A)x(B)x(C) must equal less than 120,000
9.49 x 1.181 x 10,500 = 117,680 (this is perfect)
9.49 x 1.181 x 11,000 = 123,284 (should not be run but ok for short 500’-660’drags)
9.49 x 1.181 x 11,200 = 125,526 (if it hits the rev-limiter you’re way off)

So if I'm running a 24 on the crank and a 27 on the blower I am only running 91,103 rpms on the blower @ 10,800 engine rpms.

9.49 x (24/27) x 10,800 engine rpms = 91,103 blower rpms.

Am I under driving the blower at this point? Will proper oil circulation be a concern?

Thanks.