What PSI should I see with a 3.55 pulley?
12-09-2008, 11:13 AM
#1
What PSI should I see with a 3.55 pulley? Mods:
Forged 370 9.1:1 compression
TEA stage 2 LS6 heads
EPP blower cam 240/232
LS6 intake
6 speed
Just curious on what I should be seeing. I was having belt slip on the dyno. I dont think I had the belt tight enough so I am going to change belts and tighten the hell out of it. Car made 683rwhp @ 11psi.
Forged 370 9.1:1 compression
TEA stage 2 LS6 heads
EPP blower cam 240/232
LS6 intake
6 speed
Just curious on what I should be seeing. I was having belt slip on the dyno. I dont think I had the belt tight enough so I am going to change belts and tighten the hell out of it. Car made 683rwhp @ 11psi.
12-09-2008, 11:35 AM
#2
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{[(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
if your crank pully is a different size or your blower is different just plug in the relevant numbers and rework the equation... goodluck
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
if your crank pully is a different size or your blower is different just plug in the relevant numbers and rework the equation... goodluck
12-09-2008, 03:53 PM
#3
{[(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
if your crank pully is a different size or your blower is different just plug in the relevant numbers and rework the equation... goodluck
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
if your crank pully is a different size or your blower is different just plug in the relevant numbers and rework the equation... goodluck
12-09-2008, 08:46 PM
#6
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no problem guys, just keep in mind that these equations represent the ideal conditions where you dont have the inefficiencies associated with an intercooler, pipe bends, etc... you will see less then you calculate by a significant margin based on the efficiency of your intercooler at your specific flow rate. if you need help just pm me... goodluck
