Diesel Engine Glossary
Your comprehensive guide to diesel engine terminology. From basic components to advanced remanufacturing terms, find clear definitions for industry jargon.
A
ACERT
Caterpillar's Advanced Combustion Emissions Reduction Technology. A system combining improved fuel injection, air management, and electronics for lower emissions.
B
Block
The main structural component of a diesel engine that houses the cylinders, crankshaft, and other internal components. Also called the engine block or cylinder block. Made from cast iron or aluminum alloy.
Blow-by
Combustion gases that escape past the piston rings into the crankcase. Excessive blow-by indicates worn piston rings or cylinder walls.
Boost
The positive pressure created by a turbocharger or supercharger, measured in PSI (pounds per square inch). Higher boost typically means more power.
C
C7 / C9 / C13 / C15
Caterpillar diesel engine model designations. The number roughly indicates displacement class. C15 is a popular 15.2L heavy-duty truck engine.
Camshaft
A rotating shaft with lobes (cams) that controls the opening and closing of the engine's intake and exhaust valves. Critical for proper engine timing and performance.
Common Rail
A fuel injection system where a single high-pressure fuel rail supplies all injectors. Allows precise control of injection timing and multiple injection events per cycle.
Compression Ratio
The ratio of the cylinder volume when the piston is at the bottom versus the top of its stroke. Diesel engines have high compression ratios (15:1 to 23:1) for combustion.
Connecting Rod
A metal rod that connects the piston to the crankshaft, converting the linear motion of the piston into rotational motion. Also called a con rod.
Coolant
A mixture of water and antifreeze that circulates through the engine to regulate temperature. Also called antifreeze or engine coolant.
Core
The old, worn engine that is returned when purchasing a remanufactured engine. The core is disassembled and its usable components are remanufactured.
Core Charge
A refundable deposit added to the purchase price of a remanufactured engine. Refunded when the customer returns their old engine (core) in acceptable condition.
Crankshaft
The main rotating component that converts the reciprocating motion of the pistons into rotational motion to power the vehicle. Machined from forged steel for strength.
Cylinder Head
The component that sits atop the engine block, containing the combustion chambers, valves, and often the camshaft. Houses fuel injectors in diesel engines.
D
DEF (Diesel Exhaust Fluid)
A urea-based solution injected into the exhaust stream to reduce NOx emissions in modern diesel engines with SCR (Selective Catalytic Reduction) systems.
Displacement
The total volume swept by all pistons in an engine, typically measured in liters or cubic inches. Larger displacement generally means more power potential.
DPF (Diesel Particulate Filter)
An emissions control device that captures and stores soot particles from diesel exhaust. Requires periodic regeneration to burn off accumulated soot.
Duramax
General Motors' line of diesel engines, produced in partnership with Isuzu. Popular in GM trucks and SUVs. Models include LB7, LLY, LBZ, LMM, LML, and L5P.
Dyno Testing
Testing an engine on a dynamometer to verify power output, check for leaks, and ensure proper operation before shipping to the customer.
E
EGR (Exhaust Gas Recirculation)
An emissions control system that recirculates a portion of exhaust gases back into the intake to reduce NOx emissions and combustion temperatures.
F
Fuel Injector
A precision component that sprays fuel directly into the combustion chamber at extremely high pressure. Critical for diesel engine efficiency and emissions.
H
Head Gasket
A seal between the cylinder head and engine block that prevents coolant and oil leakage while maintaining compression. A blown head gasket is a common engine failure.
Horsepower
A unit of power measuring the rate at which work is done. In diesel engines, horsepower determines the engine's ability to perform work over time.
Hot Tank
A heated chemical bath used to clean engine components by removing grease, oil, carbon deposits, and other contaminants during the remanufacturing process.
I
ISX / X15
Cummins' flagship heavy-duty diesel engine. The ISX (now X15) is a 15-liter engine widely used in Class 8 trucks. Known for reliability and performance.
L
Long Block
An engine assembly that includes the block, crankshaft, pistons, connecting rods, camshaft, and cylinder head(s). Does not include external components like the intake manifold or accessories.
M
Magnaflux
A non-destructive testing method using magnetic particles to detect cracks and flaws in ferrous metal components like crankshafts and connecting rods.
O
OEM Specifications
Original Equipment Manufacturer standards that define the exact measurements, tolerances, and materials used in factory-built engines. Remanufactured engines meet or exceed these specs.
Oil Analysis
Laboratory testing of engine oil samples to detect wear metals, contamination, and oil condition. Used to predict maintenance needs and diagnose problems.
Oil Pan
The reservoir at the bottom of the engine that holds the engine oil. Also called the sump. Contains the oil pickup tube and drain plug.
P
Piston
A cylindrical component that moves up and down within the cylinder, compressing air and receiving the force of combustion to drive the crankshaft.
Powerstroke
Ford's brand name for diesel engines used in their trucks. Includes the 6.0L, 6.4L, 6.7L, and 7.3L engines. Manufactured by International/Navistar and Ford.
R
Rebuilt Engine
An engine that has been partially disassembled and repaired, typically replacing only worn parts. Less comprehensive than remanufacturing and may not meet OEM specs.
Remanufactured Engine
An engine that has been completely disassembled, cleaned, inspected, and rebuilt with new or reconditioned parts to meet or exceed OEM specifications. Different from a rebuilt or used engine.
S
Short Block
A partial engine assembly consisting of the block, crankshaft, pistons, and connecting rods. Does not include the cylinder head(s) or camshaft.
T
Torque
A measure of rotational force, typically measured in lb-ft (pound-feet). Diesel engines are known for high torque output, essential for towing and heavy loads.
Turbocharger
A forced induction device that uses exhaust gases to spin a turbine, which compresses intake air for increased power and efficiency. Standard on most diesel engines.
V
Valve Cover
A protective cover over the cylinder head that seals the valvetrain and prevents oil leakage. Also called a rocker cover.
VGT (Variable Geometry Turbo)
A turbocharger with adjustable vanes that optimize boost across the RPM range. Provides better low-end response and top-end power. Common in modern diesel engines.
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