The boost formula, what is the 25.58 for?

DMX

Registered User
7/2.75 * 90 * 25.58 / 232 - 14.7 = my targeted boost.

All other parts of the formula make sense, the blower/crank ratio, the blower CI, the engine CI, the atmospheric pressure, but what is the significance of the 25.58?
 
I have never seen this formula before but looks like units on 7/2.75 would cancel ( i don't know what these are) if so the 25.58 would be in psi. If that helps, probably not huh.
 
Actually my guess would be the pressure of air at the temp the gas burns at. You would look this up. If gas burns at 760 degrees F then that is what my thermo book gives for pressure of air at that temp.

This could be completely wrong though, someone correct me please if it is.
 
Jeff, probably how many times the SC makes a revolution compared to the motor. ( may have a factor of 4 in there somewhere for a 4 cycle motor.)

again assumption
 
Barometric pressure. I know what the drive ratio is for but why do you have a 7 in there?

Jeff

With a 2.75:1 ratio you should make about 12.5psi
 
Last edited:
oic the 2.75 is the ratio not 7/2.75. Then I don't know what the 7 is for and the rest of my posts are worthless, because the units won't work out.
 
J57ltr said:
What's the 7/ 2.75 (2.75 =blower drive ratio) for?

Jeff

Jeff thats the formula you gave me long ago http://www.sccoa.com/forums/showthread.php?s=&threadid=7084&highlight=pulley+size

I was just curious as to what the 25.58 stood for.

The 7"/2.75" is the crank size to blower pulley size ratio I am shooting for, I am @ 2.85 right now. Remember, no jackshaft on the Taurus.

90 is the blower CID, 232 is the engine CID, 14.7 is baro pressure.

the only part you didnt explain was the 25.58, whats that all about? :)
 
Ok I see now. That comes out 2.54:1 so that would be about 10psi

I think the 25.58 is for barometric pressure.

Jeff
 
Back
Top