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04042008, 04:52 PM  #1 
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Formulas, Conversions and other junk...
I was bored and going through cleaning stuff out and came across my old school notes so I figured I’d post some of the formulas, conversions and other stuff we had to learn. Some of them are probably not going to be useful to too many people but at least they’ll be here. Never hurts to have a little pointless technical junk on a car forum…makes it look legit.
Conversions Length Millimeters to Inches x .03937 Inches to Millimeters x 25.4 Centimeters to Inches x .3937 Inches to Centimeters x 2.54 Kilometers to Miles x .6214 Miles to Kilometers x 1.609 Meters to Feet x 3.281 Feet to Meters x .3048 Weight Kilograms to Pounds x 2.205 Pounds to Kilograms x .4535 Grams to Ounces x .03527 Ounces to Grams x 28.35 Volume cc’s to cu. in. x .06102 cu. in. to cc’s x 16.388 Liters to Gallons x .2642 Gallons to Liters x 3.785 Liters to Quarts x 1.057 Quarts to Liters x .946 Milliliters to fl. oz. x .03381 fl. oz. to Milliliters x 29.58 Torque Kilogram Meters to ft. lbs. x 7.233 ft. lbs. to Kilogram Meters x .1383 ft. lbs. to Newton Meters x 1.356 Newton Meters to ft. lbs. x .737 kgm to Nm x 9.807 Nm to kgm x .102 Other Metric Horsepower (ps) to Brake Horsepower (bhp) x .9863 Brake Horsepower (bhp) to Metric Horsepower (ps) x 1.014 Kilowatts (kW) to Metric Horsepower (ps) x 1.360 Metric Horsepower (ps) to Kilowatts (kW) x .7355 Kilometers per Liter (km/l) to Miles per Gallon (mpg) x 2.352 Miles per Gallon (mpg) to Kilometers per Liter (km/l) x .4252 Spring Rates (kg/mm) to Pounds per Inch (lbs./in.) x 56.01 Kilopascals (kPa) to Pressure (psi) x .1450 Pressure (psi) to Kilopascals (kPa) x .0703 Pressure (kg/cm²) to Pressure (psi) x 14.22 General Formulas Rod Ratio = Rod Length/Stroke Torque = (HP x 5252)/RPM Horsepower (HP) = (Torque x RPM)/5252 Volumetric Efficiency (VE) = (HP x 5600)/(RPM x Disp.) Brake Mean Effective Pressure (BMEP) = (HP x 792000)/(Disp. x RPM) BMEP measured in psi Average Piston Speed (APS) = (Stroke x RPM)/6 APS measured in ft/min. Piston Acceleration (PA) = (RPM ² x Stroke/2189) x (Stroke/(2 x Rod Length) + 1) Maximum Ring Thickness = APS/PA Redline = (APS x 6)/Stroke Swept Volume (SV) = Bore ² x Stroke x 0.7854 SV = Single Cylinder Displacement Displacement (Disp.) = Bore ² x Stroke x 0.7854 x # of Cylinders Compression Ratio = (SV + CCV)/CCV CCV = Combustion Chamber Volume Head Gasket Volume (GV) = Bore ² x .7854 x Gasket Thickness Multiply by 16.387 for cc’s Net CCV = CCV + GV Cylinder Bore = √(Disp./(.7854 x # of cyl. x Stroke)) Intake Formulas Intake Tract Tuning for RPM = (1100 x Half Intake Cam Duration x 0.960)/Length = 2nd Pulse (1100 x Half Intake Cam Duration x 0.705)/Length = 3rd Pulse (1100 x Half Intake Cam Duration x 0.538)/Length = 4th Pulse Intake Tract Tuning for Length = (1100 x Half Intake Cam Duration x 0.960)/RPM = 2nd Pulse (1100 x Half Intake Cam Duration x 0.705)/RPM = 3rd Pulse (1100 x Half Intake Cam Duration x 0.538)/RPM = 4th Pulse Exhaust Formulas Mean Flow Velocity = (APS/60) x (Bore²/Exhaust I.D.²) MFV measured in ft./sec., Ideal is 280 – 300 Sonic Wave Scavenging for RPM = (950 x EX)/Length; EX = Exhaust Open # + 180° SWS for 50” or less header for top end power Sonic Wave Scavenging for Length = (950 x EX)/RPM Thermal Wave Scavenging for RPM = (1380 x EX)/Length; EX = Exhaust Open # + 180° TWS for 51” or longer header for low end power Thermal Wave Scavenging for Length = (1380 x EX)/RPM Cam and Valve Train Formulas Duration = Cam Open + Cam Close + 180° Overlap = Intake Open + Exhaust Close More overlap for high end power, less overlap for low end power Lobe Centerline = (Duration/2) – Smallest # Lobe Separation Angle = (Intake Lobe Center + Exhaust Lobe Center)/2 
04042008, 09:18 PM  #7 
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great post!
I was always somewhat confused about all the horsepower parts... It made me want to take a notepad and a pen and do some formulae! oh, and psi is pressure AS pounds per square inch hehe
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04052008, 03:45 AM  #8 
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Awesome post as I typically google this stuff as well. Thank you.
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03172013, 01:00 PM  #11 
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I always wondered Nm to ft lb and ps to bhp. Did you memorize all of these because to convert the other way you just do 1 over conversion rate.

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03172013, 04:31 PM  #12 
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Great thread. Thanks for posting. I love math!
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