How to calculate cars BHP????

Formulas for Calculating Performance
Convert 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=actual cfm / theoretical cfm x 100

street carb cfm=rpm x displacement / 3456 x 0.85

racing 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

driveshaft torque=flywheel torque x transmission ratio

Formula for instrument error

actual mph=3600 / seconds per mile

speedometer error percent=difference between actual and indicated speed / actual speed x 100

indicated distance=odometer reading at finish - odometer reading at start

odometer 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= + 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 - x track

cg height= x overall weight