how to Calculate PSI
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On The Tree
Joined: Aug 2007
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From: kuwait
how to Calculate PSI hi guys
i hope this is usefull
i have done it in excel
tell me if i am wrong
0---- damin cant install the excell here ! i will post it in here ,, if you want it by excel pvt msg me with email and i will send it
{[(crank pully diameter) / (Blower pulley diameter)] x (blower step up ratio) x (engine rpm)} / (max blower speed)... multiply that number by the max rated cfm of the blower. Store that number on paper or in your calculator... then take your discplacement in cubic inches and multiply by the same rpm used in the first equation... divide by 1728 to convert to cubic feet... divide by 2 to account for the 2 revolutions per 1 combustion cycle... now divide the first number you stored by this number... multiply this number by 14.7... this will give you your absolute pressure... then subtract 14.7... this will give you your boost pressure at the rpm you specified.
example for d1sc with 7" crank pully at 6000rpm and 370 ci of displacement...
{[(7/3.55)(4.10)(6000)] / 62000rpm} x 1400cfm = 1095.32cfm
[(370ci x 6000rpm)/ 1728] / 2 = 648.36cfm
1095.32 / 648.36 = 1.705 bar
1.705 x 14.7 = 25.066 psi absolute
25.066 - 14.7 = 10.366 psi boost at 6000 rpm
it has been taken from someone in here ,, but i have done it in excel
i hope this is usefull
i have done it in excel
tell me if i am wrong
0---- damin cant install the excell here ! i will post it in here ,, if you want it by excel pvt msg me with email and i will send it
{[(crank pully diameter) / (Blower pulley diameter)] x (blower step up ratio) x (engine rpm)} / (max blower speed)... multiply that number by the max rated cfm of the blower. Store that number on paper or in your calculator... then take your discplacement in cubic inches and multiply by the same rpm used in the first equation... divide by 1728 to convert to cubic feet... divide by 2 to account for the 2 revolutions per 1 combustion cycle... now divide the first number you stored by this number... multiply this number by 14.7... this will give you your absolute pressure... then subtract 14.7... this will give you your boost pressure at the rpm you specified.
example for d1sc with 7" crank pully at 6000rpm and 370 ci of displacement...
{[(7/3.55)(4.10)(6000)] / 62000rpm} x 1400cfm = 1095.32cfm
[(370ci x 6000rpm)/ 1728] / 2 = 648.36cfm
1095.32 / 648.36 = 1.705 bar
1.705 x 14.7 = 25.066 psi absolute
25.066 - 14.7 = 10.366 psi boost at 6000 rpm
it has been taken from someone in here ,, but i have done it in excel
Last edited by vette_c6; Apr 15, 2009 at 04:15 AM.
