Facts, Figures & Formulas
How to determine horsepower from ¼ mile times.
HP = weight x (mph divided by 234)cubed
(This works for vehicles less than 4000 pounds and running ¼ mile times
between 9 and 16 seconds)
How to determine the volume of air needed to make power at a given engine rpm.
| CFM = | engine displacement (in cubic inches) x desired rpm |
| 3456 |
How to determine compression ratio
| CR = | V1 + V2 |
| V2 |
(V1 = volume of cylinder in engine block; V2 = volume of space
above piston at TDC –
V2 includes volume of the combustion chamber plus the volume of head
gasket)
(www.csgnetwork.com/compcalc.html
,- this site allows you to play with “what-if variations to see how
they effect compression ratio)
| Cylinder volume (displacement) = | 3.14 x bore x bore x stroke |
| 4 |
Piston Speed (ft. per minute) = 2 x RPM x stroke (in feet)
| MPH = | RPM x wheel diameter (in inches) | (wheel diameter is overall including tire) |
| Gear ratio x 336 |
1 mph = 1.467 feet per second
Coil
Spring Rate
(this formula is for straight coil spring, not for a spring
that has "pig tail" style end)
k = Gd 4/8nD 3
G = modulus of rigidity -
torsion. For spring steel use 11.5 million psi
d = wire diameter in inches
n = number of free coils (a free coil is
a coil that does not touch another coil)
D = diameter of coil in inches (you can use center to center
of
wire or outside diameter + inside diamter/2)
NOTE: using inch measurements will give you rate (k) in lbs/in). Since spring rate is proportional to wire diamter to the 4th power, it is important to not include thickness of paint of powder coat in this calculation.
Acceleration or
Deceleration (g rate)
a= F/m
you can divide by 32 ft/s2 to get the number of g's. Especially useful in figuring force needed to accelerate or brake something weighing a certain amount to reach a given speed or stop in a certain amount of time.
G force in a turn - a = v 2/r. Example - you want to know how many g's in centriptal accelration (a turn or cicle) a turn rate of
1o m/s (about 48 mph) on a turn of 10m radius (about 39 feet) you are pulling 10m/s2 or just over 1 g.
Minimum Brake Fluid Boiling Points
Sea-Level Boiling Point
Dry Wet (3.7% water by volume)
Dot 3 205 C (401 F) 140 C (284 F)
Dot 4 230 C (446 F) 155 C (311 F)
Dot 5 260 C (500 F) 180 C (356 F)
Dot 5.1 270 C (518 F) 190 C (324 F)
Engine bearing and crankshaft failure causes
1. Dirt & debris in oil.
2. Lack of lubricaton from oil starvation or "dry" starts.
3. Impact to rod journal bearing surface rod stretching at top of each exhaust stroke and compression load at top of each compression stroke.
4. Bending fatigue of crank as opposed to torsional twisting. The heat generated by a bearing failure will often cause a crank to bend.
