|
1985MustangGT.com |
|
Useful Equations |

|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Air Filter Selection: |
|
|
|
|
|
|
|
|
|
An average foam filter will flow 4.38 cfm/sq-in. |
|
|
|
|
|
||
|
|
A good paper filter will flow 4.95 cfm/sq-in. |
|
|
|
|
|
||
|
|
An oiled cotton gauze (K&N) will flow 6.03 cfm/sq-in. |
|
|
|
|
|||
|
|
To get your required filtered surface area for a oiled cotton gauze filter: |
|
|
|||||
|
|
|
|
A = filtering area (square inches) |
|
|
|||
|
|
A = ( CID * RPM ) / 20839 |
CID = cubic inch displacement |
|
|
|
|||
|
|
|
|
RPM = rev./min. at max power |
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
Then using the following modifying factors if using an alternative filter media: |
|
|
|||||
|
|
|
|
|
|
|
|
|
|
|
|
A * 1.3767 = required surface area for foam element |
|
|
|
|
|||
|
|
A * 1.2181 = required surface area for paper element |
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Horsepower and Torque: |
|
|
|
|
|
|
|
|
|
HP = (TQ * RPM ) / 5252 |
|
|
|
|
|
|
|
|
|
TQ = ( HP * 5250 ) / RPM |
|
|
|
|
|
|
|
|
|
Corrected BHP = BHP * (1 - ((elevation/1000) * .03)) |
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Horsepower, ET, and Weight: |
|
|
|
|
|
|
|
|
|
A quick calculation for horsepower based on your 1/4 mile trap speed: |
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
|
|
HP = ( TS / 234 )^3 * weight |
|
HP = Horsepower |
|
|
|
||
|
|
HP = ( TS * 0.00426 )^3 * weight |
|
TS = Trap Speed (MPH) |
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
This horsepower output is the minimum required for the specified trap speed. |
|
|
|||||
|
|
It assumes ideal track conditions, weather conditions, traction, and vehicle aerodynamics. |
|
||||||
|
|
It will understate horsepower required at speeds exceeding 100 mph. |
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
|
|
ET = 5.825 * ( weight / HP )^(1/3) |
|
|
|
|
|
|
|
|
|
Weight = ( ET / 5.825 )^3 * HP |
|
|
|
|
|
|
|
|
|
HP = weight / ( ET / 5.825 )^3 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
For a quick idea of ideal ET assuming good street rubber and decent traction.... |
|
|
|||||
|
|
ET = 1363 / MPH |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Horsepower: |
|
|
|
|
|
|
|
|
|
Calculation assuming sea level and known Volumetric Efficiency |
|
|
|
||||
|
|
|
|
|
AP = pressure in psi |
|
|
||
|
|
|
|
|
CR = compression ratio |
|
|
||
|
|
HP = ( AP * CR * VE * CID * RPM ) / 792001.6 |
VE = volumetric efficiency |
|
|
||||
|
|
|
|
|
CID = cubic inch displacement |
|
|
||
|
|
|
|
|
RPM = revolutions per minute |
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
To convert from Barometric pressure in inches of mercury to psi: |
|
|
|
||||
|
|
PressurePsi = (pressureHg * 3376.85 ) / 6894.757 |
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cubic Feet per Minute: |
|
|
|
|
|
|
|
|
|
Theoretical Engine CFM = ( CID * RPM ) / 3464 |
|
|
|
|
|
||
|
|
Actual Engine CFM = ( CID * RPM * VE ) / 3464 |
|
|
|
|
|
||
|
|
Carburator CFM = ( CID * RPM * VE ) / 2820 |
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Volumetric Efficiency: |
|
|
|
|
|
|
|
|
|
VE = ( Actual CFM * 1728 ) / ( CID * RPM ) |
|
|
|
|
|
||
|
|
VE = ( Actual CFM *100 ) / ( Theoretical CFM) |
| ||||||