Psi c rotor

does anyone have a picture of a C rotor they can post or pm me, I am wanting to make sure i buy the correct one and don't get shafted, Have a D now and want to compare both Thanks all
Doug

 

differences

Screw Blower Q & A

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In an attempt to clarify the questions being asked and answered on this forum regarding screw blower displacement let me clarify and attempt to help anyone interested in this information.

PSI "D" is 422 cu.in.per/rev or 6.752 liters per/rev

PSI "C" is 476 cu.in. per/rev or 7.616 liters per/rev

Whipple R980 & A980 is 612.5 cu.in. per/rev or 9.8 liters per/rev

So if you look at SFI max overdrive based on safety and then parity based on swept volume per/rev in 1996 this is how NHRA wrote there rules,

Top Alcohol Dragster,

PSI "D" 422 cu.in. x 2.15 or 115% = 907.3

Whipple 601 cu.in. x 1.52 or 52% = 913 (.6% advantage in swept volume as it was wrote however based on the math 9.8 liters per/rev it should have read 612.5 cu.in. x 1.52 or 52% = 931 (2.6% advantage in swept volume)

Top Alcohol F/C,

PSI "D" 422 cu.in. x 2.25 or 125% = 949.6

Whipple 601 cu.in x 1.60 or 60% = 961.6 (1.2% advantage in swept volume however just as before based on the math 9.8 liters or 612.5 x 1.60 = 980 (3.2% advantage in swept volume)

Considering the fact that the swept volume per/rev is the only legitimate way to establish a fair and level playing field it is then up to the manufacture to design a supercharger that best meets the applications requirements for safe operation at a required operating overdrive limit per SFI regulations after that has been established the supercharger with the highest adiabatic and volumetric efficiency and the least parasitic loss at high20pressure with a linear airflow curve will then allow the engine to create the highest net torque/horsepower curve based on superior air delivery.

There has been a few questions about how a PSI "C" and "D" compare so here it is in overdrive a "D" at 125% would be approximately the same as a "C" at 104% so just over 10% 2.25/2.04 = 1.102 - 1 = 10.2%

The last question that comes to mind is how to tell the difference between a "D" and a "C" measure the female or driven rotor lobe thickness, there are small variation based on application and date of manufacture or customers specific needs but on average a "C" will measure .483-.485 a "D" will measure .594-.596 both blowers have a open port in the housing between the front shaft/bearing supports.
I hope this sheds some light on the questions that have been asked.

Reprint from old post I saved.I think it was from Roger.