Harry Pyle´s Calculation Scheme on Superchargers

Hi everyone, 
Lots of requests from List re Calculations...so here they are for every one.. 


To Calculate "Pulley Ratio"

PR = C(14.7 + B + I) = Crankshaft pulley Diam = Crank RPM 
         14.7xV        Blower Pulley Diam       Blower RPM 

where 
C = 1/2 Engine capacity in cc. 
B = boost in p.s.i. 
V = blower volume in cc. (bear in mind that Roots blower volume is "displacement" 
	and vane blower volume is "swept volume") 
I = Allowance for valve overlap (ie for every 10 degrees on o'lap allow 5% of the 
	boost. eg for 35 degrees, I = 3.5 x 0.05 x B ). 


To Calculate Change of Compression Ratio

RB = square root of fraction (14.7 + B) 
RA                            14.7 

Where 
RA = unblown compression ratio 
RB = new "effective" compression ratio for blown motor. 
B  = boost in p.s.i. 


To Calculate New Peak RPM 

original peak RPM x cube root of fraction (14.7 + B )= new peak RPM 
                                              14.7 
where B = Boost in p.s.i. 

Engine power band will increase by same ratio. 


Any question please ask...I have built/owned various blown cars over the years...
also single cylinder vintage motor cycle (which the experts said "couldn´t be done !!) 

Hope this helps. 

Regards Harry and Deidre