Tech Post - Formulas

The folks at NRHS were nice enough to grant me permission to use their tech library to post here for everyone to benefit from.

They do dyno tests and know their shit, plus they back up what they say about things with proof. That's the no bullshit kind of way business should be done. If you have a chance check out their site, you never know you might learn something or find some of the services they offer fit your needs.

Tell'em you seen it on The Shit Pile blog, or Stu sent you.

I don't get a discount or anything out of a referral other than maybe more access to new information to share with you guys.


With permission from and thanks to: NRHS Performance

 

Formulas

Following are some of the most commonly used formulas useful for high performance work.   Displacement from Bore and Stroke displacement = pi x (radius squared) x height example: 4 inch bore, 4 inch stroke displacement = 3.14159 x (2 squared) x 4 = 50.265ci per cylinder   Cubic Centimeters from Cubic Inches cc = (2.54 cubed) x ci example: 100ci cc = (2.54 cubed) x 100 = 1638.7cc   Cubic Inches from Cubic Centimeters ci = cc / (2.54 cubed) example: 1200cc ci = 1200 / (2.54 cubed) = 73.23ci   Horsepower from Torque and RPM hp = (torque x rpm) / 5252 example: 80 ft-lbs at 4000 rpm hp = (80 x 4000) / 5252 = 60.93hp   Torque from Horsepower and RPM torque = (hp x 5252) / rpm example: 100hp at 4000 rpm torque = (100 x 5252) / 4000 = 80 x 4000) / 5252 = 131 ft-lbs.   Average Piston Speed from Stroke and RPM average piston speed in fpm = (stroke in inches x rpm) / 6 example: 4 inch stroke at 6000rpm aps = (4 x 6000) / 6 = 4000 feet per minute   Horsepower from Quarter Mile Speed and Weight hp = ((mph / 223) cubed) x weight example: 130 mph with a 600lb bike & rider weight hp = ((130 / 223) cubed) x 600 = 118.8 hp   Horsepower from Elapsed Time and Weight hp = weight / ((ET / 5.92) cubed) example: 10 seconds ET with a 600lb bike & rider weight hp = 600 / ((10 / 5.92) cubed) = 124.5 hp   Elapsed Time from Horsepower and Weight ET = 5.92 x cube root of (weight / horsepower) example: 650lb bike with 140hp ET = 5.92 x cube root of (650 / 140) = 9.88 seconds   Quarter Mile Speed from Horsepower and Weight mph = 223 x cube root of (horsepower / weight) example: 650lb bike with 140hp mph = 223 x cube root of (140 / 650) = 133.67mph   Elapsed Time from Quarter Mile Speed ET = (1320 / mph) example: 10 second bike ET = (1320 / 10) = 132 mph   Quarter Mile Speed from Elapsed Time mph = (1320 / ET) example: 134 mph bike mph = (1320 / 134) = 9.85 seconds   Flow Bench Test Pressure Conversion Flow = (square root of (new flow pressure / known flow pressure)) x known cfm example: 160 cfm @ 10", convert to 28" Flow = (square root of (28 / 10)) x 160 = 267.7 cfm at 28"