Diesel Terminology List

2.6 Pulling Class:

Refers to a sled pulling class in which only a single turbo can feed the engine, and its inducer must measure no more than 66mm.

3.0 Pulling Class:

Refers to a sled pulling class in which only a single turbo can feed the engine, and its inducer must measure no more than 76mm (3.0 inches); military or semi axles, after market transmissions, and transfer cases are typically allowed, but stock frames are usually mandatory.

4-Pin Trailer Plug:

Transfers the tow vehicle’s 12-volt electrical system to the trailer, so brake lights, marker lights, and turn signals work; most common on older vehicles or vehicles with low towing capacities.

7-Pin Trailer Plug:

Transfers the tow vehicles 12-volt electrical system to the trailer, so brake lights, market lights, and turn signals work; standard on heavy-duty trucks.


Stands for Area/Radius (the exhaust housing size of a turbocharger), either measured in A/R or cm2.


Chemicals added to fuel in very small quantities to improve and maintain fuel quality and/or to lower emissions.

Air Intake:

The air tube and filter package that’s mounted in front of the air inlet of a turbocharger.


A process that involves milling a part out of one solid chunk of metal.


A type of diesel fuel made from blending organic-based diesel with petroleum-based diesel, along with other additives.


A measure of the amount of manifold pressure inside the engine; boost is normally measured in pounds per squar inch (psi) above atmospheric pressure.


Charge Air Cooler (see: Intercooler)

California Air Resources Board (CARB):

A state regulatory agency charged with regulating the air quality in California.

Cetane Number:

A rating for diesel fuel based on the time it takes the fuel to develop cylinder pressure after it’s injected. Also a measure of ignition quality of diesel fuel. The higher the cetane number the easier the fuel ignites when injected into an engine. Cetane number is determined by an engine test using two reference fuel blends of known cetane numbers. The reference fuels are prepared by blending normal cetane (n-hexadecane), having a value of 100, with heptamethyl nonane, having a value of 15.

Class V Hitch:

A receiver hitch rated for towing in excess of 10,000 pounds and more than 1,200 pound of tongue weight; other lesser ratings include the I, II, III, IV classes.


Diesel smoke or soot, usually used as a slang term.

Common-Rail Injection:

An injection system composed of a main pump and a common line to the injectors.  In this arrangement, the injectors (rather than the injection pump) handle injection events. A diesel fuel injection system employing a common pressure accumulator, called the rail, which is mounted along the engine block. The rail is fed by a high pressure fuel pump. The injectors, which are fed from the common rail, are activated by solenoid valves. The solenoid valves and the fuel pump are electronically controlled. In the common rail injection system the injection pressure is independent from engine speed and load. Therefore, the injection parameters can be freely controlled. Usually a pilot injection is introduced, which allows for reductions in engine noise and NOx emissions.


The intake side wheel and housing of a turbocharger.

Compressor Inducer:

The smallest diameter of the compressor wheel (typically measured in millimeters and determines the size designation of the turbo) in which un-pressurized air is brought into the turbocharger.

Compressor Exducer:

The outer diameter of the compressor wheel (measured in millimeters) where the air is being pressurized inside the compressor cover.


A Bosch pump designed for common-rail injection systems, most notably found in ’01 to ’10 LB7, LLY, LBZ and LMM Duramax diesel engines.  Also Cummins ’03 and up 5.9L and 6.7L engines.


Manufacturing engines and related power systems, Cummins Inc., is a worldwide corporation known most often in the automotive industry as the manufacturer of the engines found in the heavy-duty ’89 to ’13 Dodge and Ram pickup trucks.

DEF (Diesel Exhaust Fluid):

Diesel Exhaust Fluid; a urea-based solution used in conjunction with an SCR system to reduce emissions; DEF is a mixture of 32.5 percent automotive-grade urea and 67.5 percent de-ionized water.

Direct Injection:

A diesel fuel system that injects fuel directly onto the top of the piston without any type of pre-chamber.

DPF (Diesel Particulate Filter)

A device which physically captures diesel particulates preventing their discharge from the tailpipe. Collected particulates need to be removed from the filter, usually by continuous or periodic oxidation in a process called “regeneration”.

Drive Pressure:

The amount of pressure on the exhaust side of the engine, pre-turbocharger.

Dual Fuelers:

The slang term for a common rail diesel engine that utilizes a second (twin) high pressure fuel pump.


A 6.6L V-8 diesel engine option found in the ’01 to ’13 GMC and Chevrolet fullsize trucks and vans, produces as a joint venture between Isuzu and GM.


Engine Control Module; a computer that takes inputs from various sensors and has the basic overall job of controlling the engine’s operation.


A tuning tool for a common-rail Cummins and Duramax engines that allows access to the vehicles factory programming so changes can be made to add power and increase fuel economy.

EGR Cooler:

A radiator style cooler designed to reduce the temperature of exhaust gasses before they are re-injected into the engine’s intake tract.


Exhaust Gas Recirculation; EGR is a system that redirects exhaust gases back into the intake tract to be re-introduced into the combustion process; helps to limit NOx emissions.


Exhaust Gas Temperature; EGT is used as a measuring tool to define a point where a diesel engine can be reliably operated without harming parts; safe EGT (pre-turbo) is 1,200 degrees sustained, 1,400 degrees for short bursts, and 1,600 degrees for a few seconds.

Exhaust Brake:

A valve mounted int he diesel engine’s exhaust stream that’s used to create added exhaust pressure and increase engine braking; helpful for slowing large loads on steep downhill grades.


Fuel Control Actuator on the cp3


Fuel Injection Control Module; this computer is used to control the firing events of the injector.


A type of trailer hitch incorporating large flat plates and a locking pin; used for towing large amounts of weight.

Fire Ring:

A small steel ring that’s inserted into a machined groove in either the head or block (or both) to help contain excessive cylinder pressure due to increased power levels.

Fuel Only:

Slang term, meaning no nitrous, propane, water-methanol, or other injectables.


A large, ball-type hitch, mounted in the bed of a truck over the rear axle, used for towing large amounts of weight; allows more trailer movement over uneven terrain.

Governor Spring:

A spring or set of springs used to control peak injection pump rpm, effectively giving the engine a “redline”.


Gross Combined Weight Rating; the maximum allowed weight of a tow vehicle, all of its passengers and cargo, and a trailer.


Gross Vehicle Weight Rating; the maximum allowed weight of a vehicle (which indicates its payload capacity).

Head Studs:

Aftermarket stock sized or oversized studs that replace the head bolts for more clamping force; used to prevent a blown head gasket.


Hydraulic Electronic Unit Injector; used on 7.3l and 6.0l Power Strokes as well as other medium-duty engines; an HEUI Injector uses pressurized oil to fire the injector.


High-Pressure Oil Pump; found most commonly on 6.0L and 7.3L Power Strokes; the HPOP receives oil from the crankcase, and through the IPR, high-pressure oil is then fed to the HEUI injectors.


Injection Control Pressure; the pressurized oil value in the oil rails of an HEUI-equipped engine; typically in the range of 450-3,000 psi, or more.


Indirect Injection; an IDI engine injects fuel into a prechamber in the cylinder head before it enters the combustion area on the piston.


Injector Driver Module; sends a precise electronic current to the injector solenoid in a 7.3L Power stroke; called an FICM on the 6.0L Power Stroke.

Ignition Delay:

The length of time or number of degrees of crankshaft rotation between the beginning of injection and ignition of the fuel.

In-Direct Injection (IDI):

In diesel engines with in-direct injection the fuel is injected to an auxiliary pre-chamber. Combustion starts in the prechamber and propagates to the cylinder.

Injection Pump:

A high-pressure pump used to pressurize fuel and send it to the injectors.


A device consisting of valves, springs, a nozzle, and various passages that is actuated to spray a metered amount of fuel into a prechamber (IDI) or combustion chamber (DI).


A series of fins and tubes in a radiator-like design, used to cool off the air exiting the turbocharger, thus increasing overall efficiency by creating a denser air charge.


Injection Pressure Regulator; dump valve that sits on the HPOP outlet of an HEUI engine an dis responsible for creating pressurized oil the injectors can use.

Lift Pump:

A mechanical or electric supply pump that sends fuel from the tank to the injection pump.

Limited Slip:

A type of differential that adds traction by equalizing the output of each axleshaft through clutches, gears, or cones; these differentials are more street-able because they still allow some level of differentiation between the drive shafts to occur.


A locker is a type of differential that locks the two axleshafts together, ensuring both wheels get the same amount of power form the drivetrain.

Low Emission Vehicle (LEV):

A vehicle that is certified to meet the LEV emission standards set by the California Air Resources Board (CARB).

A module is installed somewhere in between the ECM and at least one electrical component that the ECM communicates with. When the signal leaves the ECM it travels through its normal route until it reaches the module. At this point the signal enters the module, is modified by the computer elements inside of the modules, and then exits the module and continues on its path to the desired electrical component. Some modules do not ever need to be updated due to the components that they effect. Therefore, they cannot be updated.


Also known as NOS, nitrous is short for nitrous oxide, an oxygen-bearing gas that can be injected into a diesel engine to increase the engine’s power dramatically.


Nitrogen Oxide; a tailpipe emission that is thought to be hazardous to the environment.


Stainless steel wire that’s planted into a groove cut around the combustion area of the cylinder head(s) and provides better sealing of the combustion event.


Short for ” Old Body Style”, normally in reference to the 1994.5 to 1997 Fords.


Bosch P7100 injection pump; most commonly found on 1994-1998 Dodge Rams.

Particulate Matter:

Airborne pieces of carbon, also known as smoke or soot.


Powertrain Control Module; mostly found on Ford pickup’s, the PCM integrates engine and transmission functions.

Piezo Injector:

A common-rail fuel injector that’s activated using very fast reacting piezoelectric crystals; these injectors use electricity to precisely introduce fuel into the combustion chamber and can open and close up to seven times during a single combustion event.

Power Stroke:

A line of International diesel engines found in Ford trucks from 1994.5 to 2010, the Power Stroke was available in 1994.5 to 2003 (7.3l), 2003-2007 (6.0l), and 2008-2010 (6.4l); the 2011 to present 6.7l is an in-house Ford design.


Also known as a tuner, this is a device that changes the air, fuel, timing and shifting strategies of an electronically controlled engine.

Pulse Width:

The length of time of an injection event, also known as duration or injector “on time”.

Rail Pressure:

The amount of fuel pressure in the rail of a common-rail injection system.

Rolling Coal:

Slang term used to describe the act of blowing black smoke.

S-Series Turbochargers:

A BorgWarner turbocharger designation based on frame and bearing size; most commonly used are S300?s and the larger S400?s.


Selective Catalytic Reduction; an emissions system designed to reduce NOx through the use of DEF (urea) injection; SCR works by injecting a small amount of DEF upstream of the catalyst, when the DEF enters the exhaust stream, it turns to ammonia and works with the SCR catalyst, turning NOx to nitrogen and water.

Spool Up:

The stage when a turbocharger is building boost but has not yet reached maximum boost.


Also known as an exhaust stack; an upward-exiting exhaust usually mounted through the bed, or through the hood.


A compressor device to compress the combustion air or the air/fuel mixture before it enters the engine cylinder. Superchargers are typically driven by the engine itself, through a system of gears, a belt drive, or by an electrical motor.

Super Stock:

Refers to sled pulling class in which multiple turbo-chargers can feed the engine, but it limits competitors to two stages; tube-chassis frames, military or semi axles, and aftermarket transmission and transfer cases are also allowed.


The most commonly used turbocharger mounting flange in early Cummins 5.9L applications and other pickup truck diesel applications.


Transmission Control Module; on most pickups, the TCM is integrated with the ECM to control transmission shift strategies.


Turbocharged Direct Injection; a branding of Volkswagen’s Group I-4 and V-6 turbodiesel engines.

Traction Bar:

A long rod (usually steel) mounted between frame and the rear suspension to prevent axle wrap.


The exhaust-side wheel and housing of a turbocharger.

Turbine Exducer:

The smallest diameter of the turbine wheel (measured in millimeters) taking the used exhaust gas energy and sending it out of the turbo and towards the exhaust pipe.

Turbine Inducer:

The largest diameter of the turbine wheel (measured in millimeters) that is inside the turbine housing being driven by exhaust gas pressure.

Turbo Lag:

The time delay between injecting fuel to accelerate and delivering air to the intake manifold by the turbocharger. This phenomenon may cause black smoke emissions in some turbocharged diesel engines during acceleration.


Exhaust gas-driven compressor that is used to force air into an engine and increase the intake pressure above atmospheric.


The exhaust pipes leading from the exhaust manifolds to the turbocharger.


A common agricultural fertilizer made from natural gas and one of the two ingredients in diesel exhaust fluid.

VGT (turbo):

A variable-vane, variable-geometry, or variable-nozzle turbocharger; the vanes or nozzles are used to reduce the effective A/R, improving response and spool up.


An electronic Bosch rotary pump, most often found on Cummins engines in 1999.5-2002 Dodge Ram Trucks.


A valve mounted in the exhaust system designed to release excess exhaust pressure.

Water-Methanol Injection:

A high-pressure system that injects water or water-methanol mix into a diesel engine for more power, improved efficiency, and cooler EGT.

White Smoke:

The smoke emitted during a cold start from a diesel engine, composed mainly of unburnt fuel and particulate matter.

Work Stock:

A sled pulling class typically allowing factory-appearing turbocharger rules, or having a maximum turbo inducer size rule of 2.5 inches (63.5mm).

Now that you are familiar with diesel terminology and lingo get out there and use it. If you have anymore terms you would want us to add to this list let us know!

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