Car Formulas
29-Oct-2002, 01:09 AM
#1
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Location: Cayman Islands
Posts: 1,172
Car Formulas
**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 Performance
*Convert between 1/4 mile and 1/8 mile ET's
1/4 mile ET = 1/8 mile ET x 1.5832
1/8 mile ET = 1/4 mile ET / 1.5832
*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 displacement 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
centrifugal 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 diameter
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
**Some formulas contain notation such as ^2 which means "squared" or ^3 which means "cubed"
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
1/8 mile ET = 1/4 mile ET / 1.5832
*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 displacement 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
centrifugal 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 diameter
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
29-Oct-2002, 01:32 AM
#2
!!!!AWAITING CONFIRMATION!!!!!!
Join Date: Apr 2002
Location: Ontario
Posts: 95
"She's just a cosmic girl....ohhh whoa whoa whaaaaa...
From another Galaxy...ooooo,
My heart's at zero gravity,
She's from a cosmic world,
Putting me in extacy,
Transmitting on my frequency,
She's cosmic!"
Sorry had to throw that it....Jay Kay kicks ***.
And you'd be nuts to think I'm going through that equation! lol
From another Galaxy...ooooo,
My heart's at zero gravity,
She's from a cosmic world,
Putting me in extacy,
Transmitting on my frequency,
She's cosmic!"
Sorry had to throw that it....Jay Kay kicks ***.
And you'd be nuts to think I'm going through that equation! lol
29-Oct-2002, 10:30 AM
#8
Registered User
Thread Starter
Join Date: Apr 2002
Location: Cayman Islands
Posts: 1,172
Originally posted by 1Solid_DX
cosmic girl you have alot of time on ur hands dont u
cosmic girl you have alot of time on ur hands dont u
29-Oct-2002, 10:43 AM
#10
Registered User
Join Date: Apr 2002
Location: REDLINE
Posts: 2,759
Originally posted by Cosmic Girl
Aside from the daily hassle of masturbating and trying to sell my mom for drugs. YES...I guess I do have alot of time on my hands.
Aside from the daily hassle of masturbating and trying to sell my mom for drugs. YES...I guess I do have alot of time on my hands.
so where did you find all these formulas? are they pretty accurate? cuz actually i'm in the middle of a school design project and could put some of these to good use!
29-Oct-2002, 12:42 PM
#11
Registered User
Join Date: Jun 2002
Location: Honda
Posts: 683
As an automotive Engineer, I have to say the formulas are accurate. Some of the stuff was in my High School auto shop course. (I took both auto shop with the 'rockers' and OAC math classes with the 'geeks' ... at the same time) Other formulas were in my High School Physics class and the rest were in my Engineering texts in University. I'm pretty sure though, most of this can be found in High School text material.
Mark (the 'Non-smoker'...Tina, do you remember me?)
Mark (the 'Non-smoker'...Tina, do you remember me?)
29-Oct-2002, 01:45 PM
#12
Registered User
Thread Starter
Join Date: Apr 2002
Location: Cayman Islands
Posts: 1,172
Originally posted by MY SiR
Mark (the 'Non-smoker'...Tina, do you remember me?)
Mark (the 'Non-smoker'...Tina, do you remember me?)
No lighter man!! Who never drives his car to meets 
----------------------------------------------
BTW, they are accurate, but still just so my *** is covered : Please use these formulas at your own risk!!
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