Glossary: Engine Blocks and Cylinder Heads

A protocol or set of rules established to standardize the construction and operation of onboard networks used by heavy-duty, diesel-powered commercial vehicles and off-road equipment. Protocol includes rules for identification and reporting of fault codes and construction of network messages.

The process of removing burned gases from the cylinder through the use of moving airflow pulling or extracting the gases out.

An extremely detailed analysis of the condition of the engine and the quality of the engine oil.

Two separate spring-loaded gears incorporated into a single unit to reduce gear rattle caused by torsional vibration.

A two-piece gear used in engine geartrains that forces the gears apart using spring tension. Scissor gears are used to eliminate gear backlash; also called concept gear by Cummins.

See lean NOx trap (LNT) .

An exhaust aftertreatment strategy to reduce NOx by forming ammonia, a reducing agent, using stored NOx and hydrogen from disassociated fuel molecules; stands for selective catalytic reduction-hydrogen .

An exhaust aftertreatment strategy to reduce NOx using ammonia, a reducing agent derived from liquid urea, an ammonia-carrying molecule stored in DEF; stands for selective catalytic reduction-urea .

A metering mechanism used by Caterpillar that repositions the barrel in relation to a reciprocating piston in an injection pump to change the quantity of fuel metered for injection.

A battery that has neither a liquid electrolyte nor requires the addition of water; also called a valve-regulated lead-acid battery or recombinant battery .