I have 7.625 crank pulley, 4.25 SC pulley, 4.10 (D-1SC), 6300 rpm and im seeing 8psi with 46342 Impeller RPM. Does this mean that i need 5792 rpm per psi 46342/8psi= 5792rpm/psi?

Im asking because i just bought a 8.5" crank pulley and i was wondering where it should put me in terms of boost. I know the 8.5" will put me around 51660 impeller rpm which is 5318rpm extra over the 7.625 pulley. Does this mean i will see around 1psi gain from this swap?

 

I am going to try a take a stab at this one.

If you are seeing 8 psi at an impeller speed of 46342 rpm then with an increased new impeller speed of 51660 rpm I am guessing you will see about a 2 psi increase. I calculated this using one of the "Pump Laws" that state pressure is proportional to the speed of the pump squared.

 

Can u state the formula please?

 

It is a proportion, not necessarily a formula. You can calculate it like this:

Say (P1) is your original pressure and (P2) is the final pressure, the pressure you are looking for. (N1) can be your original pump/impeller speed and (N2) will be your final pump/impeller speed.

Write: P1 over P2 is equal to N1 squared over N2 squared. From there it is just algebra, solve for the unknown P2.

I hope this helps.

Brian