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      04-04-2008, 03:52 PM   #1
sndprssr
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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
kg-m to N-m x 9.807
N-m to kg-m 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
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      04-04-2008, 04:01 PM   #2
Tom K.
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Thanks for your post. I'm always having to look most of that stuff up!
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      04-04-2008, 04:37 PM   #3
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Thanks, sndprssr! I've sticky'd this informative thread and moved it to DIY (Do-It-Yourself Instructions) forum.
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      04-04-2008, 05:30 PM   #4
sndprssr
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That's cool...didn't really know what section it should go in.
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      04-04-2008, 08:02 PM   #5
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great info
stick it, mods..
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      04-04-2008, 08:06 PM   #6
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Quote:
Originally Posted by amdmaxx View Post
great info
stick it, mods..
Ermmmmm. It is stickied. Or are you telling us to "stick it"???? :iono:
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      04-04-2008, 08:18 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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      04-05-2008, 02:45 AM   #8
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Awesome post as I typically google this stuff as well. Thank you.
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      04-27-2008, 08:00 AM   #9
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This hurts my brain like a slurpie. Thanks anyways. :respekt:
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      07-17-2012, 06:50 PM   #10
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Yes, this stuff I usually need an intenret connection for looking up.. I'll print this page and have in the garage in case power goes out!
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      03-17-2013, 12:00 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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      03-17-2013, 03:31 PM   #12
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Great thread. Thanks for posting. I love math!
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