FORMULAS

  • Conversion: 1 Liter = 61.02 Cubic Inches

  • HorsePower from MPH = (.00426 * MPH)^3 * WEIGHT

    Example: MPH=94 WEIGHT=3550 gives us: 227hp

  • ET from HorsePower = (WEIGHT / HP)^.333 * 5.825

    Example: WEIGHT=3550 HP=227 gives us: 14.55sec 1/4 mile

  • CFM = (CID/2)*(RPM/1728)*VE

    Example: CID=305 RPM=4500 VE=.75 gives us: 297cfm 

    VE = volumetric efficiency
VE is appoximately equal to 0.8 for hi-perf street engine 
and approx. equal to 0.9+ for full race engines.
This gives rather low values for CFM but is probably all you really need.
  • TORQUE = (5245 * HP) / RPM

    Example: HP=227 RPM=4500 gives us: 264lb/ft

  • HorsePower from MPH = WEIGHT * (MPH/234)^3

    Example: WEIGHT=3550 MPH=94 gives us: 230hp

  • HorsePower from ET = WEIGHT * (5.825/ET)^3

    Example: WEIGHT=3550 ET=14.55 gives us: 228hp

  • Tire height (inches) = {[(section width * profile) / 2540] + (wheel diameter / 2)} * 2

    Example: (255/60R15) gives us: 27.04" (larger than factory size)

    Example: (245/60R15) gives us: 26.57" (larger than factory size)

    Example: (235/60R15) gives us: 26.10" (same as factory size)

    Example: (225/60R15) gives us: 25.62" (smaller than factory size)

    Example: (215/65R15) gives us: 26.00" (factory size)

    Example: (275/50R15) gives us: 25.82" (very close to factory size)

  • 60 foot time from ET = (.12 * 1/4 mile et) + .17

    Example: 60' time = (.12 * 14.90) + .17 = 1.958 seconds

  • Top Speed (mph) = (see example)

    Example: 

    	Redline = 5400
	Top Gear (trans) = 0.67:1
	Rear end gear = 3.73:1
	Tire height = 27"
	PI = 3.14
	
5400/0.67 = 8059.70 driveshaft RPM

8059.70/3.73 = 2160.77 wheel RPM

2160.77*27*3.14 = 183190.08 inches/minute

183190.08*60 = 10991404.80 inches/hour

10991404.80/12 = 915950.40 feet/hour

915950.40/5280 = 173.47 MPH

* This number assumes no resistance of any kind. This top speed is theoretical.
You will probably never actually see this top speed in your car, but it is useful to 
determine a ballpark limit. Using this number you can factor in rolling
friction and wind drag to get a closer number.

    

    

    

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