Aftertreatment System
A system that reduces exhaust NOx and particulate emissions.
Bar
A unit of pressure approximately equal to atmospheric pressure at sea level (approximately 14.5 lbs per square inch).
Camshaft
A shaft that is moved by the cranksaft with two or more offset cams (lobes), which operate the valves.
Combustion
The process in which a substance reacts with oxygen creating heat and light (burning).
Compression
A phase in the working of an internal combustion engine where a combination of fuel and air is compressed in a cylinder before being ignited.
Crank/Crankshaft
A rod that spins and drives a piston movement in the cylinder.
Crank Angle
The angle between the crankshaft and top dead center of the piston.
Cylinder
The central working part of a reciprocating (or piston) engine, the space through which a piston travels.
Exhaust
The gases ejected from an engine as waste.
Flame Speed
The fuel's ability to undergo controlled combustion without detonation. Flame speed can be used as a measure of efficiency.
Fuel Injection
A system for mixing fuel with air. Fuel injection atomizes the fuel by forcibly, pumping it through a small nozzle under high pressure.
Inlet Valve
A one way valve that allows air into a compressor.
Jake Brake (Compression Release Engine Brakes)
A trademark for engine brakes developed/manufactured by Jacobs Vehicle Systems. The braking system modifies engine valve operation, using engine compression to slow the vehicle. It is primarily used on semi-trucks or other large vehicles and is known for being extremely loud.
Knock
The result of when combustion starts off correctly, but one or more pockets of the air and fuel mixture explodes outside the envelope of the normal combustion front. This causes timing to be thrown off, creating a shock wave that makes a pinging sound and increases cylinder pressure dramatically. The effect of engine knock ranges from inconsequential to completely destructive.
Miller Cycle
A combustion process for the four stroke internal combustion engine first used by Ralph Miller in the 1940s. The cycle forces the intake valve to be left open longer than it would be in an Otto Cycle engine. In effect, the compression stroke is two discrete cycles: the initial portion when the intake valve is open and final portion when the intake valve is closed.
Miller Effect
The effect of the Miller Cycle is a lower final charge temperature allowing ignition timing to be advanced beyond what is normally allowed before the onset of detonation. The result is an increase in overall efficiency and a reduction of NOx emissions.
Naturally Aspirated
An internal combustion engine devoid of forced induction methods.
NOx
A chemical term for nitrogen oxides produced during combustion and a contributor to smog and acid rain.
Otto Cycle
A four-stroke cycle for internal combustion engines:
(1) Suction of gas/air into the firing cylinder;
(2) Compresstion, ignition, explosion;
(3) Expansion of gasses; and
(4) Expulsion of the products of combustion from the cylinder.
Invented by Beau de Rochas in 1862, and applied by Dr. Otto in 1877 in the Otto-Crossley Gas Engine was the first commercially successful internal combustion engine.
Outlet Valve (Exhaust Valve)
A one-way valve that allows compressed air out of a compressor.
Piston
A rod inside a cylinder that is moved by pneumatic pressure.
Poppet
A valve mechanism that continually opens and closes in response to variations in pressure.
Poppet Valve
A pneumatic control valve that redirects the flow of gas when actuated.
Power
The rate which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time.
Power Curve
The graphical representation of the changing relationship between speed and revolutions per minute (RPM).
Pressure Volume (PV) Curve
A graphical representation of the changing relationship between pressure and volume in the cylinder during engine cycles. A PV curve or diagram shows the impact of early or late ignition timing at peak cylinder pressure.
Regenerative Braking
A system seen in hybrid vehicles that takes energy normally wasted during braking and turns it into usable energy. This energy is saved in a storage battery and used to power the motor whenever the vehicle is in electric mode.
Spark Plug
An electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark.
Split-Cycle Engine
A type of internal combustion engine that divides four cylinder strokes between two paired cylinders, one for intake/compression and another for power/exhaust.
Supercharger
An air compressor used for forced induction of an internal combustion engine. The forced induction creates a greater mass flow-rate providing more oxygen to support combustion than would be available in a naturally-aspirated engine. This increase in flow-rate allows more fuel to be provided and more work to be done per cycle, increasing power output.
Thermal Efficiency
The ratio of engine work to heat energy of consumed fuel.
Thermodynamics
The study of relationship between thermal energy (heat) and all other forms of energy (i.e. mechanical, electrical).
Top Dead Center, After Top Dead Center (ATDC)
The position of a piston that is farthest from the crankshaft (at its highest point). The Scuderi Engine fires ATDC, meaning the piston has just begun moving toward the crankshaft
Turbocharger
An air compressor used for forced induction of an internal combustion engine. Like a supercharger, it serves to increase the mass of air entering the engine to create more power. However, a turbocharger differs in that the compressor is powered by a turbine driven by the engine's own exhaust gases.
Volumetric Efficiency
The ratio of fuel and air entering the cylinder to the capacity of the cylinder under static conditions.