In a world growing ever more divided by differences in people, politics, and religion, it’s surprising that we have found common ground in the realm of emissions. Specifically, the regulations governing internal combustion engines (tailpipe emissions). This article will focus on how global emission regulations standards of Diesel engines have converged and how this affects you and your business.
Before discussing the regulations, let’s first clarify what we’re measuring (1) and how we measure it (2). The first part is straightforward: regardless of where a Diesel engine is produced or operated, the potential pollutants emitted from its tailpipe are the same. These regulated pollutants include: • Carbon monoxide (CO). • Hydrocarbons (HC), regulated either as total hydrocarbon emissions (THC) or as non-methane hydrocarbons (NMHC). • Nitrogen oxides (NOx), composed of nitric oxide (NO) and nitrogen dioxide (NO2). • Particulate matter (PM).
Some governing bodies use a single combined limit for HC + NOx emissions rather than setting separate limits for each. Additionally, certain emission regulations include limits for particle number (PN) emissions and/or smoke opacity. Greenhouse gas (GHG) emission regulations often set limits on carbon dioxide (CO2) emissions, and may also impose limits on other GHGs, such as nitrous oxide (N2O) and methane (CH4). Some of these pollutants have proven easier to control than others.
The second part, “How these pollutants are measured,” is more complex to explain. Emissions are measured during an engine or vehicle test cycle designed to create consistent measurement conditions while simulating the real-world operating conditions of a given application. Emission cycles consist of a sequence of speed and load conditions performed on either an engine or chassis dynamometer. Emissions measured on a vehicle (chassis) dynamometer are typically expressed in grams of pollutant per unit of distance traveled (ex: g/km or g/mi).
In contrast, emissions measured using an engine dynamometer test cycle are expressed in grams of pollutant per unit of mechanical energy produced by the engine (ex: g/kWh or g/bhphr). Test cycles can be classified into steady-state cycles and transient cycles. Steady-state cycles involve a series of constant engine speed and load modes, with emissions analyzed for each mode and then averaged to produce an overall result.
Transient cycles, on the other hand, simulate a prescribed driving pattern that includes WWW.DIESEL.ORG 23 accelerations, decelerations, and variations in speed and load.
And now the unfortunate part… Regulatory authorities in different countries have not agreed on a uniform set of emission test procedures, leading to the use of various test cycles, such as the Heavy-Duty Federal Test Procedure (FTP) in the United States and the World Harmonized Transient Cycle (WHTC) in Europe and parts of Asia. Since exhaust emissions vary with engine speed and load conditions, measurements from different test cycles may not be directly comparable, even if expressed in the same units.
Comparing emission standards between countries is not as straightforward as simply comparing numbers, but a clear trend does emerge from the data (see chart). Whether we’re discussing US2007, Euro VI, or Japan 2016 regulations, the trend indicates that restricting tailpipe emissions for Diesel engines is a global phenomenon. Although their testing cycles differ, their overall emission levels are relatively close to each other. Proposed future regulations, such as US2027 and Euro VII, suggest that this trend will continue.
So, what does this mean for us as Diesel specialists, and why does this trend matter? Perhaps the real question is… How have these incredibly low reductions in tailpipe emissions been achieved? Significant advancements in exhaust aftertreatment systems have played a role, including improved catalyst coating “recipes” and refined reductant dosing strategies. Turbocharging technology has also played a significant role. While its advancements may not be as profound as those in other areas, its importance in reducing emissions cannot be denied.
However, the most significant change has been in fuel injection systems. Over the past decade, injection pressures have reached previously unimaginable levels. Closed-loop control, where injectors report each injection event back to the ECM, has introduced a new level of precision. Internal injector design has led to drastic reduction in over-flow quantity which results in better system efficiency.
This has significantly enhanced the combustion process in the cylinder due to the increased speed and accuracy of fuel injection. It’s these advancements that have allowed engine out emissions to be the lowest in history. Advanced fuel system technologies, such as Delphi F2 and F3, Bosch VCC/NCC, and Denso G4S/P, are now being universally adopted across global markets, demonstrating how tighter tailpipe emissions regulations have brought us all together.
This presents an opportunity for global collaboration, encouraging us to cross national boundaries when seeking knowledge, tooling, or even parts. While component numbers/applications may be unique to a region, the technologies no longer are. You might find that your challenges are not exclusive and that other colleagues in the industry may have already addressed similar issues.
As Diesel specialists, we should embrace this global association and work together to overcome these obstacles.
