Guest blog: How do you solve a problem like off-highway vehicle emission testing?

Across the European automotive and off-highway industry, more stringent emissions standards are being implemented for internal combustion engines to improve air quality and reduce greenhouse gas emissions to meet the global 1.5°C target and Net Zero. For passenger cars and commercial vehicles, the industry is being driven to transition to electric vehicle technologies to reduce tailpipe emissions. However, due to the power and energy demands for larger off-highway machinery applications, internal combustion engines are still the leading technology and have not been forgotten. Globally, the non-road mobile machinery (NRMM) sector is experiencing increased legislative demands for engine emissions with EU Stage V and China IV, while Indian Bharat Stage V and US Tier V will follow in the near future.

Engine emissions across the automotive and off-highway industry have been under increased scrutiny since the ‘Dieselgate’ scandal came to light in 2015, instigating major transformation. Europe was at the forefront of radical legislation change for NRMM applications, with EU Stage V requiring in-service testing of machine engine emissions during end user operation. This is alongside the already existing laboratory-based evaluations for Type Approval that enable sale onto the European Union market. The rollout started with non-road equipment, such as diggers and excavators, but things changed substantially at the end of 2022.

Since then, the regulation for NRMM in-service monitoring (ISM) of emissions (EU2016/1628 amendment EU2022/2387) expanded the scope to include a larger number of NRMM machine categories beyond the initial non-road equipment with engines between 56 and 560kW. Under the terms of the regulation, the engine manufacturer is required to perform ISM of emissions, namely: carbon monoxide (CO); carbon dioxide (CO₂); nitrogen oxides (NOx) and total hydrocarbon emissions (THC). Testing is completed during the machine’s usual operation with its typical operator; however, where this is not possible engine manufacturers do have the option of performing a representative duty cycle, which is agreed with the Type Approval authority.

Additionally, for machines with smaller engines, such as snowmobiles, ATVs, tillers and lawnmowers (Groups E, I, O, P), due to practical challenges installing Portable Emissions Measuring Systems (PEMS), the engine manufacturer has the option to remove the engine and aftertreatment and perform the in-service monitoring test on the engine dynamometer using a representative duty cycle. Right now, the regulation is in a monitoring phase, therefore gathering data for the emissions performance of a wide range of machines for the European Commission, however it is expected in the future that the regulation will be amended to introduce limits that the engine manufacturers must conform to in-service.

As the scope increase suggests, the EU Stage V NRMM ISM emissions regulation covers a plethora of machines that fit into one of 16 ISM groups, depending on engine power rating and category – from trains through to excavators, boats and large generators. It’s a vast number of vehicles and for engine manufacturers who might use the same powertrain in two different applications – say, an excavator and a generator – they need to ensure that the engine emissions performance is satisfactory during the test in both (or all) the applications in which it is deployed. Depending on the machine type and group, testing method selected and engine production date, engine manufacturers have a deadline of either 26 December 2024, 2025, or 2026 to complete the testing requirement. Ahead of the test programme, the engine manufacturer must submit its ISM plan to the Type Approval authority to define the testing method, engine family selection and number of engines it plans to test.

Whilst those dates might seem like some time in the future, engine manufacturers are urged to ready themselves as soon as possible due to the extent of preparation required, which includes securing test machinery, upskilling staff to the test requirements and securing test equipment, as well as actual completion of the analysis.

The NRMM ISM testing process typically consists of the following stages. Firstly, the test preparation, which involves PEMS calibration, quality checks and machine preparation activities, such as inspection and suitability checks, fluid sampling and fuelling. Then, the PEMS is installed, which includes fabrication of the exhaust to flow tube adaptors and mounting the PEMS on the machine under test. Following this, the PEMS and machine is set up for test, which includes entering the machine information, equipment setup parameters, ECU datalogging and selecting the correct machine operation mode.

As mentioned, the actual ISM test itself can be completed during a machine’s typical operation or using a representative duty cycle. PEMS measurement of gaseous emissions, ambient conditions, location (GPS) and engine ECU data is collected, which is then post-processed and reported as per the regulatory requirements. Here, calculations are made using the data collected and reports are generated, which enable the engine manufacturer to submit the findings to the approval authority. Finally, the test equipment is removed from the machine under test and the machine returned to its normal condition to complete the process.

There is nothing to stop engine manufacturers carrying out these extensive tests themselves; however, it would mean significant investment in hardware for the PEMS technology and associated equipment, not to mention costs and time associated with upskilling staff to meet the test and regulatory expertise requirements. Some major OEMs might be in a position to make such investments, but for many engine manufacturers, using the wider test-service supplier industry with the existing equipment and expertise is a much more efficient route to achieve the end goal.

HORIBA MIRA has first-hand experience of successfully delivering NRMM ISM testing for several globally renowned OEMs. In 2022, HORIBA MIRA travelled to the Netherlands to complete an NRMM ISM test programme for an off-highway machine OEM on ten of its 16- to 32-tonne wheeled and crawler excavators. Two of the core team – which consisted of one engineer, one engineering technician, two technicians and one programme manager – travelled to the recommended EU NRMM test site and conducted the testing across two test trips in just six weeks. HORIBA MIRA was responsible for rental of all test machines and arranging transport to the test site, providing all required test equipment and shipping to the test location, arrangement of a test site, and providing competent personnel to conduct the test programme. Such flexibility and know-how around emissions testing could prove invaluable at a time when demands and tight timescales are being placed on businesses from all sides.

Daniel Newson - Project Engineer, HORIBA MIRA