J-Rod

CAR MATH FORMULA'S
N1) Many of the formulas use the value of pi which is 3.1415927
N2) Some formulas contain notation such as ^2 which means "squared"
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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 cylinder.
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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
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Formulas for piston speed
piston speed in fpm = stroke in inches x rpm / 6
rpm = piston speed in fpm x 6 / stroke in inches
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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
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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
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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
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Formulas for tire size & their effect
tire diameter = 2 x selection width x aspect ratio / 2540 + rim diameter
effective ratio = old tire diameter / new tire diameter x original ratio
actual mph = new tire diameter / old tire diameter x actual mph
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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
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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
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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
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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
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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

FEAR THE LS1

iTrader: (1)

Here's mine...

Alot of compression + alot of lift = fast.

hehe

Damn J-Rod I think you got them all covered already! Nice list. Thanks!
Lee

avezz28

Can you expain in detail how to calculate the center of gravity?

SMOKIN01TA

iTrader: (10)

- alot of weight = faster.

J-Rod

TTT

Predicting Power

BHP = PLAN/33,000
P is brake mean effective pressure, in PSI
L is piston stroke, in feet
A is the area of one piston, in square inches
N is the number of power strokes per minute


Piston Speed

Cm = .166 x L x N
Cm is mean piston speed, in feet per minute
L is stroke, in inches
N is crankshaft speed, in RPM

Brake Mean Effective Pressure (BMEP)

2-Stroke BMEP = (HP x 6500)/(L x RPM)
4-Stroke BMEP = (HP x 13000)/(L x RPM)

L = Displacement in Liters

i.e., 80 cc = .08 Liters
1 ci. = 16.39 cc

Piston Acceleration

Gmax = ((N^2 x L)/2189) x (1 + 1/(2A))
Gmax is maximum piston acceleration, in feet per second squared
N is crankshaft speed, in RPM
L is stroke, in inches
A is the ratio of connecting rod length, between centers, to stroke

Piston Stroke Motion
S = R cos X + L cos Z
S = the distance piston wrist pin is from center of crankshaft
R = the radius of the crankshaft wrist pin
L = the length of the connecting rod
X = the angle of the wrist pin
Z = the angle of the connecting rod
or
sin X = R/L sin Z

Piston Travel vs. Crank Rotation

d = ((S/2) + L) - (S/2 cos X) - L sin[cos-1 (S/2L sin X)]
S = Stroke (mm)
L = Connecting Rod Length (mm)
X = Crank Angle Before or After TDC (deg)
Note: (L) Rod Length is usually 2 times the (S) Stroke
OR
For Spreadsheets and some Calculators
HT = (r + c) - (r cos (a)) - SQRT(c^2 - (r sin (a))^2)
r = s/2
dtor = PI/180
a = d x dtor
HT = The height of piston
r = The stroke divided by 2
c = The rod length
a = The crank angle in radians
d = The crank angle in degrees
dtor = Degrees to Radians

Exhaust Systems Tuned Length

Lt = (Eo x Vs) / N
Lt is the tuned length, in inches
Eo is the exhaust-open period, in degrees
Vs is wave speed in feet per second (1700 ft/sec at sea level)
N is crankshaft speed, in RPM
Length of Curved Pipe
L = R x .01745 x Z
L is length
R is radius of the pipe bend
Z is the angle of the bend
Diffuser Proportions
D2 = SQRT( D1^2 x 6.25 )
D2 is the diffuser outlet diameter
D1 is the diffuser inlet diameter
6.25 is the outlet/inlet ratio constant
Baffle Cones
Lr = Le/2
Lr is mean point of the reflection inside the baffle cone
Le is the length of the baffle cone

Port Open Time

T = ( 60/N ) x ( Z/360 ) or T = Z/( N x 6)
T is time, in seconds
N is crankshaft speed, in RPM
Z is port open duration, in degrees

Compression Ratio

CR = ( V1 + V2 ) / V2
CR is compression ratio
V1 is cylinder volume at exhaust closing
V2 is combustion chamber volume

Carburetor Throttle Bore Diameter

D = K x SQRT( C x N )
D is throttle bore diameter, in millimeters
K is a constant ( approx. 0.65 to 0.9, derive from existing carburetor bore)
C is cylinder displacement, in liters
N is RPM at peak power

Crankcase Volume

Primary compression ratio =
Case Volume @ TDC / Case Volume at BDC
or
CRp = V1 + V2 / V1
CRp is the primary compression ratio
V1 is crankcase volume @ BDC
V2 is piston displacement

Resonance Effects

F = Vs / 2¼ * the square root of A / Vc (L + 1/2 the square root of ¼ A
Vs is the sonic speed Uusually about 1100 ft/sec)
A is the cross-sectional area of the inlet
L is the inlet pipe length
Vc is the flask (crankcase) volume

Average Exhaust Temperature

Determine the exhaust gas temperature in Kelvin
(k = C + 273.15). This is usually a function of the engine's BMEP.

Torque

1.00 lb-ft = 0.138 kg-m = 1.35 N-m
1.00 kg-m = 7.23 lb-ft. = 9.81 N-m
1.00 N-m = 0.102 kg-m = 0.737 lb-ft

Mass

1.00 lb = 0.454 kg = 4.45 N
1.00 kg = 2.20 lbs = 9.81 N
1.00 N = 0.102 kg = 0.220 lb

Distance

1 in = 2.54 cm = 0.0000158 mi = 0.0000254 km
1 cm = 0.394 in = 0.00000621 mi = 0.00001 km
1 ft = 30.5 cm = 0.000189 mi = .000305 km
1 mi = 63,360 in = 160,934.4 cm = 1.609 km
1 km = 0.621 mi = 100,000 cm = 3281 ft

Pressure

1.00 bar = 14.5 psi = 1.02 kg/sq-cm = 100 kPa
1.00 psi = 0.069 bar = 0.070 kg/sq-cm = 6.89 kPa
1.00 kg/sq-cm = 0.980 bar = 14.2 psi = 98.1 kPa
1.00 kPa = 0.010 bar = 0.145 psi = 0.010 kg/sq-cm


Temperature

F = 9 / 5 x C + 32
C = 5/9 (F - 32)
K = C + 273.4

Area / Volume

1.00 sq-in = 6.452 sq-cm
1.00 sq-cm= 0.155 sq-in
1.00 cu-in = 16.387 cc
1.00 cc = 0.0610 cu-in

Power

1.00 HP = 746 W
torque (lb-ft) = 5252 x hp / rpm
hp = rpm x torque (lb-ft) / 5252 The Weight of Air
14.7 lbs. per sq. inch at sea level.


Air Density Calculation
StdAirDensity = 1.22556 and is defined at 59.0F degrees, 0.0% humidity, and 29.92 inches on the barometer.

Temp_c = (Temp-32.0) * 5.0 / 9.0;
Temp_k = Temp_c + 273.0;
Baro_mb = Barometer / (29.92 / 1013.0);
Baro_pa = Baro_mb * 100.0;
SaturationPressure_mb = 6.11 * pow(10,(7.5*Temp_c)/(237.7+Temp_c));
VaporPressure_mb = Humidity * SaturationPressure_mb / 100.0;
TempVirtual_k = Temp_k / (1.0 - (VaporPressure_mb/Baro_mb)*(1.-0.622));
// D = P/(T*R)
AirDensity = Baro_pa / (TempVirtual_k*GasConstant);
% Std Density = AirDensity/StdAirDensity*100

J-Rod

Additional Conversion Factors
1 Centimeter - 0.0328084 foot; 0.393701 inch

1 Circular Mil - 7.853982 x 10 to the negative seventh square inches; 5.067075 x 10 to the negative sixth square centimeters

1 Cubic Centimeter - 0.061024 cubic inch; 0.270512 dram (U.S. fluid); 16.230664 minims (U.S.); 0.999972 milliliter

1 Cubic Foot - 0.803564 bushel (U.S.); 7.480520 gallons (U.S. liquid); 0.028317 cubic meter; 28.31605 liters

1 Cubic Inch - 16.387064 cubic centimeters

1 Cubic Meter - 35.314667 cubic feet; 264.17205 gallons (U.S. liquid)

1 Foot - 0.3048 meter

1 Gallon (U.S. liquid) - 0.1336816 cubic foot; 0.832675 gallon (British); 231 cubic inches; 0.0037854 cubic meter; 3.785306 liters

1 Grain - 0.06479891 gram

1 Gram - 0.00220462 pound (avoirdupois); 0.035274 ounce (avoirdupois); 15.432358 grains

1 Hectare- 2.471054 acres; 1.07639 x 10 to the fifth square feet

1 Inch - 2.54 centimeters

1 Kilogram - 2.204623 pounds (avoirdupois)

1 Kilometer - 0.621371 mile (statute)

1 Liter - 0.264179 gallon (U.S. liquid);0.0353157 cubic foot; 1.056718 quarts (U.S. liquid)



1 Meter - 1.093613 yards; 3.280840 feet; 39.37008 inches

1 Mile (statute) - 1.609344 kilometers

1 Ounce (U.S. fluid) - 1.804688 cubic inches; 29.573730 cubic centimeters

1 Ounce (avoirdupois) - 28.349523 grams

1 Ounce (apothecary or troy) - 31.103486 grams

1 Pint (U.S. liquid) - 0.473163 liter; 473.17647 cubic centimeters

1 Pound (avoirdupois) - 0.453592 kilogram; 453.59237 grams

1 Pound (apothecary or troy) - 0.3732417 kilogram, 373.24172 grams

1 Quart (U.S. dry) - 1.10119 liters

1 Quart (liquid) - 0.946326 liter

1 Radian - 57.295779 degrees

1 Rod - 5.0292 meters

1 Square Centimeter - 0.155000 square inch

1 Square Foot - 0.09290304 square meter

1 Square Inch - 645.16 square millimeters

1 Square Meter - 10.763910 square feet

1 Square Yard - 0.836127 square meter

1 Ton (short) - 907.18474 kilograms

1 Yard - 0.9144 meter


POWER - AC CIRCUITS
Efficiency = 746 x Output HP / Input Watts
3ø KW = Volts x Amps x PF x 1.732 / 1000
3ø Amps = 746 x HP / 1.732 x Eff. x PF
3ø Eff. = 746 x HP / 1.732 x Volts x Amps x PF
3ø PF = Input Watts / Volts x Amps x 1.732
1ø KW = Volts x Amps x PF / 1000
1ø Amps = 746 x HP / Volts x Eff. x PF
1ø Eff. = 746 x HP / Volts x Amps x PF
1ø PF = Input Watts / Volts x Amps
HP (3ø) = Volts x Amps x 1.732 x Eff. x PF / 746
HP (1ø) = Volts x Amps x Eff. x PF / 746
1 KW = 1000 Watts

Eff. = Efficiency, PF = Power Factor, KW = Kilowatts, HP = Horsepower

POWER - DC CIRCUITS

Torque = HP x 5280 / RPM
HP = Torque X RPM / 5280
1 HP = 36 lb.in. @ 1750 RPM
1 HP = 3 lb. ft. @ 1750 RPM

Eff. = Efficiency, HP = Horsepower
OHMS LAW

Volts (E) = Amps (I) x Ohms (R)
Amps (I) = Volts (E) / Ohms (R)
Ohms (R) = Volts (E) / Amps (I)

R=Ohms, E=Volts, I=Amperes

To figure miles per hour, multiply the engine RPM by the Wheel Diameter in inches and divide this by the Gear Ratio times 336
or
MPH = RPM * wheel diameter (in inches) / gear ratio * 336


To figure engine speed (RPM), multiply by the Speed in MPH, by the rear axle gear ratio times 336. Divide this by the tire diameter in inches.

or

RPM = MPH * gear ratio * 336 / tire diameter

J-Rod

Weight of Fuel

The Specific gravity of 92-octane gasoline is 0.75
Leaded race and unleaded 87-octane street gasolines can test below 0.75.
(Specific gravity is the weight of a material relative to that of water.)

1 Gallon of Water Weighs 8.03 lbs

1 Gallon of Gasoline Weighs 6.02 lbs

Air Consumption

A gasoline racing engine consumes about 1.3 to 1.4 cfm of air per HP.

An alcohol racing engine consumes about 1.2 to 1.3 cfm of air per HP.

BSFC

Brake Specific Fuel Consumption is a formula to determine the efficiency of an engine.

The formual is:

Fuel (in pounds) consumed per hour / Engine Horsepower

A 1,000 hp engine with a BFSC of 0.5 would consume 500 lbs of fuel per hour (83 gallons).

Racing engines BSFC values usually range from 0.4 to 0.48

Carburetor Flow Rating

Four-barrel carburetors are rated at 1.5 inches HG (mercury) (20.3 inches water)

Two barrel carburetors are rated at 3.0 inches HG (mercury) (40.6 inches water)

EGT
Exhaust Gas Temperature of a gasoline racing engine should be 1350º F - 1400º F.


Horsepower and torque
BHP = T x RPM ./. RPM
or
T = 5252 x BHP ./. RPM
BHP = Brake horsepower
T = Torque (ft/lbs)
RPM = Engine speed in revolutions per minute
horsepower = rpm x torque / 5252
torque = 5252 x horsepower / rpm

Valve Spring Rate
R = (OL - CL) ./. (IH - OH)
R = valve spring rate
OL = open load
CL = closed load
IH = installed height (closed height)
OH = Open height

J-Rod

Formula Spreadasheet

http://www.parkercarburetion.com/Cal...ngFormulas.xls

J-Rod

Horsepower based on ET HP = Weight / (ET / 5.825)^3


Horsepower based on Trap Speed HP = (MPH / 234)^3 x Weight

AZ28DRIVER1

all you need is this website

http://www.smokemup.com/auto_math/index.php

Just enter your data and it will do all the calculations for you

smokemup

iTrader: (6)

Thanks.

J-Rod... I haven't heard of taxable HP....
taxable horsepower = bore2 x cylinders / 2.5

Please explain.

FASTONE

Nice work J -rod!!How bout this :Lots of dollars +well chosen parts +hard work=more hp and or faster car!

Don"t pick the cam with the biggest #"s


Don"t campare your(similar) combo of parts to someone else"s and expect the same hp!


Asking to pick a cam-doing a search=stupid responses+harsh remarks!!

Old SStroker

Of what?

For a complete vehicle it's probably easier to measure than to calculate.
Basically you "scale" the car or check the weight on each wheel with the car sitting level. You then raise either the front or rear some distance (2 ft or so), and recheck the weights on the two wheels. A few moment calculations and you have CG.

It's a little more complex in reality. You can't let suspension move, fluids like fuel mess up the calculations, and the second measurement is sometimes difficult to get correct.

Oh, you can find left-right location also with these calcs.

For non round parts, it's probably still easier to measure than calculate. Hanging the part or assembly from cables (or wires for small parts) at different orientations and projecting the wire line thru the part will give pretty good results.

For a complete engine or engine/trans combo, using the vehicle scaling method would work

Any particular thing you want to find CG of?

SAPPER

iTrader: (10)

Here's the best calculation:
LS1 + heavy foot + anyone able to drive a straight line = Mustang Killer
Hehehehehehe, one for the ford crowd.

FASTONE

Maybe she"s a better driver then you !

Nine Ball

iTrader: (38)

TTT for new forum

DanO

www.onlineconversion.com

I'll throw up some eqations later

bshell

iTrader: (24)

Fuel related equations:

One of the most common questions relating to engine fueling is:
How much hp can my injectors support?
Max fwhp = (Injector Flow Rate)(# of cylinders)(Injector Duty Cycle)/(bsfc)

Finding the flow rate of an injector rated at a different pressure:
Injector Flow Rate(new) = [sqrt(new fuel pressure)/sqrt(old fuel pressure)]*Injector Flow Rate(old)

Common values for BSFC:
NA: 0.4 - 0.5
Nitrous: 0.5 - 0.6
FI: 0.6 - 0.7

Cstraub

iTrader: (1)

Capacity of oil pan:
Sump length x sump width x sump depth x .0172 = capacity in qts

ls1290

iTrader: (20)

Is there any way to calculate rear wheel horsepower or torque based on vehicle weight, vehicle speed, vehicle acceleration, and engine RPM?

Keith