Terms and definitions related to the advanced diesel technologies involving engines, components like turbochargers and emissions control technology. Advanced technologies have helped diesel evolve to achieve near zero emissions and increased efficiency. Some of these innovations include:

Closed Crankcase Filters

Closed crankcase filters are used to reduce emissions from crankcase breather tubes in most turbocharged aftercooled diesel engines by using a multi-stage filter designed to collect, coalesce, and return the emitted lube oil to the engine's sump.


Common Rail Fuel Injection

Advanced fuel pump technology is part of the new fuel control system in advanced diesel engines. By directly feeding the injectors from a single fuel pump, an electronic system is incorporated which precisely controls the pressure and timing of fuel injection. A more advanced and efficient common rail injection system is the Piezo Common Rail which, is available in automotive applications.

Diesel Oxidation Catalysts (DOCs)

Like catalytic converters already used on all new gasoline vehicles, diesel oxidation catalysts (DOCs) cause chemical reactions to reduce emissions without being consumed, and without any moving parts.

  • The catalysts reduce particulate emissions by as much as 50%.

  • The catalysts can reduce the invisible gaseous ozone-forming hydrocarbons (HC) by more than 70% and carbon monoxide emissions by as much as 90%.

  • DOCs have been equipped on hundreds of thousands of off-road diesel engines worldwide for decades, and on millions of heavy-duty highway trucks since 1994 in the US.

  • DOCs can be installed on new vehicles or in some cases can be retrofitted on vehicles already in-use.

  • DOCs can be used with conventional diesel fuel, biodiesel and emulsified diesel fuels, ethanol/diesel blends, as well as other alternative diesel fuels.


Diesel Particulate Traps

A high-efficiency diesel particulate trap removes particulate matter (PM) in diesel exhaust by filtering exhaust from the engine. The filter systems can reduce PM emissions by 80 to greater than 90%.

Electronic Engine Controls

Computers monitor and control a full array of engine performance including engine timing, precision fuel injection strategies, air management and turbocharging. They provide real-time feedback for the engine to optimize efficiency and performance based on the load demands.


Glow Plugs

Typically comprised of a heating coil in a metal tube closed at one end and filled with electrically insulating ceramic powder. These plugs help quickly start advanced engines.


Improved Combustion Chamber Configuration

In an improved combustion chamber configuration, the cylinder head has been shaped to provide the proper space in which fuel/air mixture will ignite and burn most effectively, creating maximum power stroke.

NOx Absorbers

NOx adsorber technology is a catalyst technology for removing nitrogen oxides (NOx) in a lean (i.e., oxygen-rich) exhaust environment for both diesel and gasoline lean-burn direct-injection engines. NOx adsorber technology has made significant progress and is currently being optimized for diesel engine emission control. Reductions in engine out NOx emissions of as high as 90% have been demonstrated and it appears possible to develop the system into a functional and durable NOx control system for diesel exhaust.

Selective Catalytic Reduction

  • Selective Catalytic Reduction (SCR) is one of the most cost-effective and fuel-efficient vehicle emissions control technologies available to reduce diesel engine emissions Selective catalytic reduction (SCR) systems use a wash-coated or homogeneous extruded catalyst and a replenishable chemical reagent (diesel exhaust fluid, DEF) to convert NOx to molecular nitrogen and oxygen in the exhaust stream. In mobile source applications, an aqueous urea solution is usually the preferred reductant.

  • As exhaust and reductant pass over the SCR catalyst, chemical reactions occur that reduce NOx emissions. SCR systems can reduce NOx emissions by 75 to 90%, Hydrocarbon (HC) emissions by up to 80%, and PM emissions by 20 to 30%.

  • SCR has been successfully used to reduce emissions from stationary industrial processes for over half a century. Since 2010 it has become increasingly used in many mobile source applications, including line-haul trucks, off-road equipment, marine vessels, and locomotives.



Utilizes energy from the engine exhaust to boost performance. Exhaust gas drives a turbine wheel that turns another turbine wheel in the intake air stream forcing more air into the cylinder, reducing emissions, and increasing performance. Many turbochargers today are variable geometry designs which can precisely adjust the flow rate and volume of air to optimize combustion based on the real-time load demands on the engine.

Ultra-Low Sulfur Fuel (ULSD)

Ultra-low sulfur diesel fuel is highly refined for clean, complete combustion and low emissions enabling the use of emissions treatment systems. It has been the standard fuel for diesel in the US since 2010 for both on and off-road applications. Some fuel retailers now offer “auto-diesel” which can have higher ignition properties (higher cetane levels) than standard diesel and are targeted toward diesel pickup truck, SUV, and van owners.

Variable Injection Timing

Electronically controlled high-pressure fuel injector releases the precise amount of fuel at the moment of maximum compression (when the piston reaches the top of the cylinder).


Wall-Flow Diesel Particulate Filter

High efficiency filters are extremely effective in controlling the carbon fraction of the particulate, the portion that some health experts believe may be the PM component of the greatest concern.

Since the volume of particulate matter generated by a diesel engine is sufficient to fill up and plug a reasonably sized filter over time, some means of disposing of this trapped particulate must be provided. The most promising means of disposal is to burn or oxidize the particulate in the filter, thus regenerating, or cleansing, the filter. This is accomplished through the use of a catalyst placed either in front of the filter or applied directly on the filter, a fuel-borne catalyst, or burners which are used to oxidize or combust the collected particulate.

Around the world, more than 200,000 DPFs have also been installed as retrofits on existing engines and equipment. DPFs have also been used for successfully for decades on a variety of off-road engines since the mid-1980s.