Jargon buster! A simple guide to key abbreviations and buzzwords from the world of power technology and emissions regulations

Application – is usually used to describe the vehicle type or machine an engine powers.

AdBlue – also known as DEF or diesel exhaust fluid. This is a colourless, odourless liquid comprising urea and water. It is used to break down NOx emissions from a diesel engine fitted with a selective catalytic reduction (see SCR) exhaust aftertreatment system.

CO2 – Carbon dioxide. Another by-product from combustion which is relative to the amount of fuel burned. Higher fuel efficiency means less CO2 emissions, which is why Cummins Inc. continues to invest more than $600m annually in advancing cleaner diesel engine technology.

CO2 is a greenhouse gas (GHG). New CO2 Heavy Duty Vehicle (HDV) regulations in Europe come into force in 2025 and will mandate CO2 reductions across the commercial vehicles industry on an increasing scale to 2040. Find out more about this regulation here: [Link to CO2 article]

DOC – Diesel oxidation catalyst is part of the exhaust aftertreatment system. This substrate has a catalytic coating within its honeycomb structure that passively oxidises soot particles (see PM) and any unburnt fuel from the exhaust. It can also be used to burn fuel to create the heat needed to perform an active regeneration of the DPF.

DPF – A diesel particulate filter features a semi-porous (usually ceramic) core, which traps particulates (see PM and PN) in the exhaust stream as they pass through it. This trapping process is typically >99.9% efficient. The particles are then removed through oxidation during either passive or active regeneration. In ‘passive regeneration’, the flow of NOx (see NOx) is used to oxidise carbon particles. In an ‘active regeneration’, fuel is burned over the DOC (see DOC) to elevate DPF temperatures to the point that the carbon particles are oxidised by excess oxygen in the exhaust gas.

Duty-cycle – refers to vehicle or machine’s operating pattern, or how it is used. Can also be referred to as the ‘use-case’. Duty cycle can be characterised in various ways, including peak or average engine power, time spent at idle and miles covered.

ECM or ECU – Engine control module / unit. This is the engine’s brain and is used to control emissions by managing conditions inside the combustion chamber. The ECM does this by changing the fuel injection timing and pressure, managing the airflow with a variable geometry turbocharger or throttle and adjusting the exhaust gas recirculation (EGR) valve, where fitted. The whole system is balanced to provide the best end-user experience (performance, fuel and AdBlue/DEF consumption) while meeting cutting edge emissions standards.

EGR – Exhaust gas recirculation is the process whereby a percentage of the diesel engine’s exhaust gases are redirected back into the combustion cylinder, in order to help reduce oxides of nitrogen emissions (see NOx).

Euro 7 – Is the next generation of emissions regulation in Europe, coming into force in 2028. For heavy-duty trucks and buses, it establishes more stringent limits for various pollutants, including those that were not regulated at Euro VI, such as nitrous oxide (N2O). There will also be stricter lifetime requirements for all vehicles in terms of both mileage and years, which now goes up to 875,000 km or 15 years (whichever is first) for heavy-duty trucks and 375,000 km or 10 years for medium-duty trucks.

European CO2 Heavy Duty Vehicle regulations - The European Council has formally adopted an amendment to CO2 emission standards for heavy-duty vehicles (HDVs). The regulation, which has now been published in the Official Journal of the EU, makes almost all new HDVs - including commercial and vocational trucks, urban buses and coaches – subject to stricter carbon emissions reduction targets. Starting in 2025 with a fleet average reduction of 15%, by 2040 most commercial vehicles will need to meet a 90% CO2 reduction target. 

Exhaust aftertreatment – The technology which reduces emissions in an internal combustion engine’s exhaust gas, after it has left the engine. In a Euro VI diesel engine this is typically a diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR).

GHG – Greenhouse gas. These are gases that contribute to the greenhouse effect and include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) among others. Upcoming CO2 HDV Regulations and Euro 7 specify strict limits for emissions of this type.

mg/kWh – Milligrams/kilowatt-hour is the unit of measurement for the constituents of a diesel engine’s exhaust as currently used within the Euro emission legislation scheme.

NOx – Oxides of nitrogen. The collective term for gaseous emissions composed of nitrogen and oxygen - NO and NO2. They are formed during high temperature combustion. Aftertreatment systems are used to minimise NOx emissions from diesel engines. At Euro 7, NOx emissions limits have been reduced from 460mg/kWh to 200mg/kWh in laboratory test conditions and from 690 mg/kWh to 260 mg/kWh in real driving conditions.

N2O – Nitrous oxide is a greenhouse gas generated as a by-product when a selective catalytic reduction system eliminates NOx from the exhaust gas. Selective catalytic reduction material composition and effective temperature control can reduce N2O. Euro 7 regulations specify strict N2O limits.

OBD – On-board-diagnostics are the section of the engine’s electronic control system which monitors the emission control system to ensure it is working correctly. If the OBD detects a failure that could result in a higher level of emissions it alerts the driver to the problem, logs the fault in the engine’s control unit (ECU), and advises the driver to visit their service workshop. In certain cases that could be construed as tampering, it can even de-rate (‘power down’) the engine.

OBM - On-board monitoring. Euro 7 will introduce stricter requirements, meaning the OBM system in each vehicle will record its tailpipe emissions status and make it available remotely for evaluation.

PM – Particulate matter is a directly emitted complex mixture including nitrates, sulfates and solid carbon fraction (soot) by-products of combustion. Lower temperature or incomplete combustion increases PM. In Cummins Euro VI engines, particulate filters are used to reduce PM emissions by around 99%.

PN – Particulate number measures emissions of solid particles. At Euro 7, the size of particles measured has been reduced to 10 nm (PN10), versus 23 nm (PN23) as at Euro VI.

SCR – Selective catalytic reduction is an exhaust aftertreatment technology that injects AdBlue / DEF into the hot stream of exhaust gases where it breaks down into ammonia. The ammonia is then used by the catalytic convertor to convert NOx into harmless nitrogen gas (N2) and water vapour (H2O). A very small amount of N2O is also generated as a by-product of this reaction.

Test Cycle – The process of measuring emissions from a diesel engine based on a legislative standard i.e. Euro VI or Euro 7. Different test cycles are used by different bodies around the world. At Euro 6, the WHDC (World Harmonized Duty Cycle) was stipulated for the certification of new low-emission engines as it represents a typical ‘driving period’ for a truck or bus and is the basis for the transient and steady state test cycles used in laboratories. At Euro 7 there will be a much stronger focus on real driving emissions. Cummins has recently invested more than $16 million in a new powertrain test facility to support Euro 7 test requirements. 

VECTO - Vehicle Energy Consumption Calculation Tool (VECTO). This data is mandatory for new trucks, buses and coaches above 3500 kg gross vehicle weight (GVW) and must be made publicly available by OEMs who report the data to the government annually. VECTO utilises engine, powertrain and vehicle data, with parameters such as rolling resistance, air drag, masses and inertias, to simulate CO2 emissions across heavy duty vehicles.

Compliance with CO2 HDV reduction targets, assessed via VECTO, is based on CO2 emissions at the tailpipe as a result of fuel consumption. It doesn’t capture the small amounts of CO2 generated by AdBlue/DEF consumption or lubrication oils burning or what is produced through non-green hydrogen or electricity to charge batteries.