Velocityfps = 1.467 x MPH MPH = Velocity in miles per hour fps = Velocity in feet per second Horsepower and torqueBHP = T x RPM ./. RPM or T = 5252 x BHP ./. RPM BHP = Brake horsepower T = Torque (ft/lbs) RPM = Engine speed in revolutions per minute DisplacementV = K x B* x B x S x N V = Engine displacement B = Cylinder bore S = Stroke N = Number of cylinders K = 3.1416 ./. 4 = .7854 Valve Spring RateR = (OL - CL) ./. (IH - OH) R = valve spring rate OL = open load CL = closed load IH = installed height (closed height) OH = Open height Rod RatioRR = L ./. R RR = Rod ratio L = center to center length of rod R = stroke Starting RatioManual transmissionSR = AR x FG SR = starting ratio AR = axle ratio FG = first gear ratio of transmission Automatic transmissionSR = AR x FG x TR TR = torque converter torque ratio at stall Mile per hourMPH = (RPM x R) ./. (168 x AR) RPM = revolutions per minute R = rolling radius of driving tire (inches) AR = Overall gear reduction Many of the formulas use the value of pi which is 3.1415927 Some formulas contain notation such as ^2 which means "squared" or ^3 which means "cubed" Formulas for Calculating PerformanceConvert between 1/4 mile and 1/8 mile ET's 1/4 mile ET = 1/8 mile ET x 1.5832 (thanks to Bobby Mosher for this formula) 1/8 mile ET = 1/4 mile ET / 1.5832 (thanks to Bobby Mosher for this formula) Calculate 1/4 mile ET and MPH from HP and Weight ET = ((Weight / HP)^.333) * 5.825 MPH = ((HP / Weight)^.333) * 234 Calculate HP From ET and Weight HP = (Weight / ((ET/5.825)^3)) Calculate HP From MPH and Weight HP = (((MPH / 234)^3) * Weight) Formulas for displacement, bore and stroke pi/4 = 0.7853982 cylinder volume = pi/4 x bore^2 x stroke stroke = displacement / (pi/4 x bore^2 x number of cylinders) Formulas for compression ratio (CylVolume + ChamberVolume) / ChamberVolume cylinder volume = pi/4 x bore^2 x stroke chamber volume = cylinder volume / compression ratio - 1.0 displacement ratio = cylinder volume / chamber volume amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke Formulas for piston speed piston speed in fpm = stroke in inches x rpm / 6 rpm = piston speed in fpm x 6 / stroke in inches Formulas for brake horsepower horsepower = rpm x torque / 5252 torque = 5252 x horsepower / rpm brake specific fuel consumption = fuel pounds per hour / brake horsepower bhp loss = elevation in feet / 1000 x 0.03 x bhp at sea level Formulas for indicated horsepower & torque horsepower = mep x displcement x rpm / 792,00 torque = mep x displacement / 150.8 mep = hp x 792,000 / displacement x rpm mep = hp x 792,000 / displacement x rpm mechanical efficiency = brake output / indocated output x 100 friction output = indicated output - brake output taxable horsepower = bore2 x cylinders / 2.5 Formulas for air capacity & volumetric efficiency theoretical cfm = rpm x displacement / 3456 volumetric efficiency = acutal cfm / theoretical cfm x 100 street carb cfm = rpm x displacement / 3456 x 0.85 racin carb cfm = rpm x displacement / 3456 x 1.1 Formulas for tire size & their effect effective ratio = (old tire diameter / new tire diameter) x original ratio actual mph = (new tire diameter / old tire diameter) x actual mph Formulas for g force & weight transfer drive wheel torque = flywheel torque x first gear x final drive x 0.85 wheel thrust = drive wheel torque / rolling radius g = wheel thrust / weight weight transfer = weight x cg height / wheelbase x g lateral acceleration = 1.227 x raduis / time^2 lateral weight transfer = weight x cg height / wheel track x g centrufugal force = weight x g Formulas for shift points rpm after shift = ratio shift into / ratio shift from x rpm before shift drivehsaft torque = flywheel torque x transmission ratio Formula for instrument error actual mph = 3600 / seconds per mile speedo error percent = difference between actual and indicated speed / actual speed x 100 indicated distance = odometer reading at finish - odometer reading at start odo error percent = difference between actual and indicated distances / actual distance x 100 Formulas for MPH RPM gears & tires mph = (rpm x tire diameter) / (gear ratio x 336) rpm = (mph x gear ratio x 336) / tire daimeter gear ratio = (rpm x tire diameter) / (mph x 336) tire diameter = (mph x gear ratio x 336) / rpm Formulas for weight distribution percent of weight on wheels = weight on wheels / overweight x 100 increased weight on wheels = [ distance of cg from wheels / wheelbase x weight ] + weight Formulas for center of gravity cj location behind front wheels = rear wheel weights / overall weight x wheelbase cg location off-center to heavy side = track / 2 - [ weight on light side / overall weight ] x track cg height = [ level wheelbase x raised wheelbase x added weight on scale / distance raised ] x overall weight |
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