| Watts Shop Performance |
| Calculations and Caculator |
How to figure MPH at any given RPM, tire diameter, rearend gear ratio and transmission gear or
vise versa.
vise versa.
RPM x Tire Diameter
------------------------------------------------------------------- = MPH
Rearend gears x Trans Gear Ratio x 336
------------------------------------------------------------------- = MPH
Rearend gears x Trans Gear Ratio x 336
How to figure Carburetor CFM.
Engine CI Maxium RPM
---------------------- X -------------------------- = CARB. CFM
2 1728
---------------------- X -------------------------- = CARB. CFM
2 1728
For easer use.
Engine CID x Maxium RPM
------------------------------------------------------------ = Carb. CFM
3456
------------------------------------------------------------ = Carb. CFM
3456
How to figure valve-open duration from cam card.
BTDC + ABDC + 180 = Number of Degrees (Duration)
180 is the degrees of a full intake stroke
Formula can figure Exhaust also ATDC + BBDC + 180 = Duration
Formula can figure Exhaust also ATDC + BBDC + 180 = Duration
How to figure pressure ratio for boost.
14.7 + Boost
PR = ------------------------------
14.7
PR = ------------------------------
14.7
Example for 5 psi of boost
14.7 + 5 (psi)
PR = --------------------------- = 1.34
14.7
1.34 is 34% more air going into the engine
Example #2 for 12 psi of boost
14.7 + 12
PR = --------------------------- = 1.82
14.7
That 82% more air going into the engine
14.7 + 5 (psi)
PR = --------------------------- = 1.34
14.7
1.34 is 34% more air going into the engine
Example #2 for 12 psi of boost
14.7 + 12
PR = --------------------------- = 1.82
14.7
That 82% more air going into the engine
How to figure Air Flow Rate.
CID x RPM x 0.5 x EV
Air Flow Rate = ----------------------------------------------
1728
Air Flow Rate = ----------------------------------------------
1728
Example of a 302 Mustang
302 x 5500 x 0.5 x 0.85
Air Flow Rate = ------------------------------------ = 408 CFM
1728
302 x 5500 x 0.5 x 0.85
Air Flow Rate = ------------------------------------ = 408 CFM
1728
How to figure Air Filter Flow Lost
Standard Barometric Pressure
Air Filter Flow Loss = ----------------------------------------------------------------------- -1 = ?
Standard Barometric Pressure - Loss through filter
Air Filter Flow Loss = ----------------------------------------------------------------------- -1 = ?
Standard Barometric Pressure - Loss through filter
Gauge reads 3 inches of vacum under maxium load.
30
Air Filter Flow Loss = ------------------------------------ -1 = 11% Loss
30 - 3
Air Filter Flow Loss = ------------------------------------ -1 = 11% Loss
30 - 3
How to convert cc/min to lb/hr.
Cubic Centimeters Pounds
--------------------------- = ---------------- X 10.5
Minute Hour
--------------------------- = ---------------- X 10.5
Minute Hour
How to calculate injector size for a given application.
Expected BHP X 0.55
Pounds of Fuel Per Hour Per Injector = ------------------------------------------
Number of Injectors
Pounds of Fuel Per Hour Per Injector = ------------------------------------------
Number of Injectors
How to figure Duty Cycle.
Stock Pulse Duration
Duty Cycle = --------------------------------
Time of one Revolution
Duty Cycle = --------------------------------
Time of one Revolution
Example :
5.0 msec
Duty Cycle = ------------------ = 0.67 = 67%
7.5 msec
5.0 msec
Duty Cycle = ------------------ = 0.67 = 67%
7.5 msec
How to figure Performance Gain.
Desired Horsepower
Performance Gain = ---------------------------------- -1 = ?
Original Horsepower
Example :
275 + 100
----------------------- -1 = 0.36 =36%
275
Performance Gain = ---------------------------------- -1 = ?
Original Horsepower
Example :
275 + 100
----------------------- -1 = 0.36 =36%
275
How figure Horsepower.
Horsepower = Torque x RPM
-------------------------
5252
-------------------------
5252