VOTC = Valve Opening at Top dead Center
TDC = Top Dead Center
BDC = Bottom Dead center
Advance = Moving the timing backwards closer or “sooner” in rotation of the rotor - points & crankshaft angle.
Retard = Moving the timing forward away or “farther” in rotation of rotor - points.
Dwell = Amount of time it takes for a coil to energize before distributing electricity through the ignition system.
Firing order = An organized order of certain amount of cylinders in an engine firing or “igniting” at a given point in the cycle of each cylinder.
THG = Tapered Hook Groove
Tolerance = A specific “gap” between 2 parts in a given unit for operating properly
VPC = Valve to Piston clearance
Valve spring bind = When a higher lift camshaft is used will sometimes cause the spring itself to “bind” from being compressed too much. This generally happens when somebody uses factory springs with larger lift Hi-po cam. That means the valve seat must be cut deeper to acquire the higher spring w/ larger lobed camshaft & update to a stronger spring.
MEP = Mean Effective Pressure (Pressure during each of the 4 strokes)
NA = Naturally aspirated
NOS = Nitrious Oxide System
Installed height = The physical height of the valve spring when securely installed with keepers & retainer.
Spark blowout = Can be caused by excessive spark plug gap or highly turbulent combustion chamber environment. Such conditions can occur because of Blowers, turbos or other superchargers. Also high compression.
FPS = Feet per second (piston speed)
FPM = Feet per minute (piston speed)
RPM = Repetition Per Minute (crankshaft, camshaft)
Stoichiometric mixture = 14.7:1 of A/F - Chemically correct
Rich stoichiometric ratio is considered below 14.7 :1
Lean stoichiometric ratio is considered above 14.7 :1
Ignition delay = The actual period after the spark has occurred until the fuel begins to burn and flame propagation starts.
Flame propagation = The spreading of the flame within an area. The propagation can change speeds as turbulence gains intensity while compression pressure rises. Higher pressures are caused by the valve timing, crankshaft angle, piston design. Higher turbulence can be done by turbo or blower/supercharger also.
Turbulence = A disruption in flow of air through a given passage or area.
Audible detonation = Non silent occurrence inside the combustion chamber
Inaudible detonation = Silent occurrence inside the combustion chamber
Inaudible & Audible detonation occur because of carbon or foreign matter stuck to the piston face or cylinder head chamber. This causes more or additional unwanted rise in compression, which in turn, ignites the lower octane rated fuels sooner than the actual spark ignition.
Reversion = Backwards flow of exhaust gases or intake A/F mixture.
Standoff = A/F mixture gets pushed out the induction system
BTU = British Thermal Unit
Over-square engine = Bore is larger than the stroke
Under-square engine = Stroke is larger than the bore
Square engine = Stroke & bore is the same length
MOI = Moment of Inertia
I know there is plenty more out there. I am not looking for extreme scientific names, but if that (whatever it is) is the only word or phrase for a certain occurrance that is complex, so be it. So if you can guys, please add more vocab w/ definition to the list. Its very appreciated!
