SBM head velocities and there application?
I'm trying to come to grips with this part of head performance, people talk about velocities a lot when discussing heads, carbs, headers etc... But in an vague abstract way no definitive numbers on what the head velocity is for a given head and what those head velocities will work with (cid x rpm). I hope we can figure out the velocities of the heads we generally have available and what displacements and rpms they work best with.
Now I'm not saying these formulas and these fps guidelines are 100% accurate and if people have better ones and or reasons why these guidelines and formula's are wrong or somewhat wrong, feel free to post. But I figured we'd start here with these.
Induction Formulas
Average_CSA = Port_Volume_CC / (Port_CenterLine_Length * 16.387)
MIN CSA = (Bore x Bore x Stroke x RPM x .00353) / 613.8 (.55 MACH)
Port_Volume_CC = Average_CSA * Port_CenterLine_Length * 16.387
Port_CenterLine_Length = Port_Volume_CC / ( Average_CSA *16.387 )
FPS = ( Flow_CFM * 2.4 ) / Average_CSA
Flow_CFM = Average_CSA * FPS * .4166667
Average_CSA = ( Flow_CFM * 2.4) / FPS
cfm demand = cid x rpm x .0009785 / # of cylinders
I'm trying to come to grips with this part of head performance, people talk about velocities a lot when discussing heads, carbs, headers etc... But in an vague abstract way no definitive numbers on what the head velocity is for a given head and what those head velocities will work with (cid x rpm). I hope we can figure out the velocities of the heads we generally have available and what displacements and rpms they work best with.
Now I'm not saying these formulas and these fps guidelines are 100% accurate and if people have better ones and or reasons why these guidelines and formula's are wrong or somewhat wrong, feel free to post. But I figured we'd start here with these.
Induction Formulas
Average_CSA = Port_Volume_CC / (Port_CenterLine_Length * 16.387)
MIN CSA = (Bore x Bore x Stroke x RPM x .00353) / 613.8 (.55 MACH)
Port_Volume_CC = Average_CSA * Port_CenterLine_Length * 16.387
Port_CenterLine_Length = Port_Volume_CC / ( Average_CSA *16.387 )
FPS = ( Flow_CFM * 2.4 ) / Average_CSA
Flow_CFM = Average_CSA * FPS * .4166667
Average_CSA = ( Flow_CFM * 2.4) / FPS
cfm demand = cid x rpm x .0009785 / # of cylinders