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Automotive Mathematical Formulas

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Below is a listing of common mathematical formulas as they apply to Corvettes and automobiles in general. Please note that many of the formulas listed use the value of pi which is 3.1415927

Chassis and Powertrain Formulas
Air Capacity & Volumetric Efficiency Formulas
    » High Perf. Carburetor CFM = RPM x Displacement / 3456 x 1.1
    » Street Carburetor CFM = RPM x Displacement / 3456 x 0.85
    » Theoretical CFM = RPM x Displacement / 3456
    » Volumetric Efficiency = Acutal CFM / Theoretical CFM x 100
Bore, Stroke and Displacement Formulas
    » Cylinder Volume = pi/4 x Bore2 x Stroke (pi/4 = 0.7853982)
    » Stroke = Displacement / (pi/4 x bore2 x number of cylinders)
Brake Horsepower Formulas
    » BHP Loss = Elevation in Feet / 1000 x 0.03 x BHP at Sea Level
    » Brake Specific Fuel Consumption = Fuel Pounds Per Hour / Brake Horsepower
    » Horsepower = RPM x Torque / 5252
    » Torque = 5252 x Horsepower / rpm
Center of Gravity Formulas
    » Center of Gravity Location (behind front wheels) = Rear Wheel Weights / Overall Weight x Wheelbase
    » Center of Gravity Location (off-center to heavy side) = Track / 2 - [ Weight on Light Side / Overall Weight ] x Track
    » Center of Gravity Height = [ Level Wheelbase x Raised Wheelbase x Added Weight on Scale / Distance Raised ] x Overall Weight
Compression Ratio Formulas
    » Amount to Mill = (New Displacement Ratio - Old Displacement Ratio / New Displacement Ratio x Old Displacement Ratio) x Stroke
    » Chamber Volume = Cylinder head cc + gasket cc + dish of piston cc (or) - dome of piston cc
    » Compression Ratio = (Cylinder Volume + Chamber Volume) / Chamber Volume
    » Cylinder Volume = pi/4 x bore(2) x stroke
    » Displacement Ratio = Cylinder Volume / Chamber Volume
G-Force & Weight Transfer Formulas
    » Centrufugal Force = Weight x G
    » Drive Wheel Torque = Flywheel Torque x First Gear x Final Drive x 0.85
    » G = Wheel Thrust / Weight
    » Lateral Acceleration = 1.227 x Raduis / Time2
    » Lateral Weight Transfer = Weight x Center of Gravity Height / Wheel Track x g
    » Weight Transfer = Weight x Center of Gravity Height / Wheelbase x G
    » Wheel Thrust = Drive Wheel Torque / Rolling Radius
Indicated Horsepower and Torque Formulas
    » Friction Output = Indicated Output - Brake Output
    » Mechanical Efficiency = Brake Output / Indicated Output x 100
    » MEP = HP x 792,000 / Displacement x RPM
    » Taxable Horsepower = Bore2 x Cylinders / 2.5
    » Torque = MEP x Displacement / 150.8
Instrument Error Formulas
    » Actual MPH = 3600 / seconds per mile
    » Indicated Distance = odometer reading at finish - odometer reading at start
    » Odometer Percent Error = difference between actual and indicated distances / actual distance x 100
    » Speedometer Error Percent = difference between actual and indicated speed / actual speed x 100
Piston Speed Formulas
    » Piston Speed in FPM (Feet Per Minute) = Stroke in inches x RPM / 6
    » RPM = Piston Speed in fpm x 6 / Stroke in inches
Tire Size & Effect Formulas
    » Actual MPH = (New Tire Diameter / Old Tire Diameter) x Actual MPH
    » Effective Ratio = (Old Tire Diameter / New Tire Diameter) x Original Ratio
    » Gear Ratio = (RPM x Tire Diameter) / (MPH x 336)
    » MPH = (RPM x Tire Diameter) / (Gear Ratio x 336)
    » RPM = (MPH x Gear Ratio x 336) / Tire Diameter
    » Tire Diameter = (MPH x Gear Ratio x 336) / RPM
Transmission Shift Point Formulas
    » RPM After Shift = Ratio Shift Into / Ratio Shift From x RPM Before Shift
    » Drivehsaft Torque = Flywheel Torque x Transmission Ratio
Weight Distribution Formulas
    » Percent of Weight on Wheels = Weight on Wheels / Overweight x 100
    » Increased Weight on Wheels = [ Distance of Center of Gravity from Wheels / Wheelbase x Weight ] + Weight

Performance Formulas
1/4 mile and 1/8 mile Elapsed Time Conversions
    » 1/4 mile ET = 1/8 mile ET x 1.5832
    » 1/8 mile ET = 1/4 mile ET / 1.5832
1/4 mile Elapsed Time and MPH from Horsepower and Weight
    » ET = ((Weight / HP).333) * 5.825
    » MPH = ((HP / Weight).333) * 234
Horsepower From Elapsed Time and Weight
    » HP = (Weight / ((ET / 5.825)3))
Horsepower From MPH and Weight
    » HP = (((MPH / 234)3) * Weight)

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