Tougher truck emissions laws hasten innovation

The California Air Resources Board's August 2020 initiative sets out stringent new emissions limits for diesel-engined trucks from 2024. Engine manufacturers are likely to turn to innovative technologies like cylinder deactivation to meet the new regulations, which will invariably trickle down to other world markets in due course.

Let's take a closer look at what CARB's latest emissions regulations entail, and what's being done to ensure truck makers are on track to meet them...

California has been at the forefront in engine emissions legislation since the 1980s and sooner or later all US states and most countries – including Australia – have followed its lead. Critics of ever-more-stringent emissions regulations, meanwhile, point out the complexity and costs of compliance, often without considering the obvious advantages of modern engines in terms of reliability, performance and economy.

The latest Californian initiative is a step up from the current US equivalent of Euro VI, while we still have only Euro V here in Australia. The August 2020 California Air Resources Board (CARB) initiative requires truck manufacturers to reduce emissions below Euro VI levels for diesel-powered vehicles with 10,000lb (4.5 tonnes) or greater GVM by 2024.

The next stage requires makers to transition from diesel trucks and vans to electric zero-emission trucks by 2045, when every new truck sold in California must be zero-emission.

"California is an innovation juggernaut that is going electric," said Jared Blumenfeld, California's Secretary for Environmental Protection. "We are showing the world that we can move goods, grow our economy and finally dump dirty diesel."

Although CARB has led this latest emissions charge, the United States Environmental Protection Agency (EPA) is also moving to strengthen the heavy-duty engine emission standards, with a focus on oxides of nitrogen (NOx) emissions under real driving conditions, including low-speed urban driving.

However, the EPA's Cleaner Trucks Initiative (CTI) is targeting US-wide implementation somewhat later than in California, from 2027.

Virtually every diesel truck emissions law since the 1980s has been greeted with protest by global engine makers, but almost all of them have managed to comply (Caterpillar being a notable exception). There have been additional costs, but the modern truck diesel performs much better, for longer and with much better fuel economy than pre-emissions engines.

In California, light, medium and heavy trucks – 4.5 tonnes GVM and above – are the largest single source of air pollution from vehicles. They're responsible for 70 per cent of smog-causing pollution and 80 per cent of carcinogenic diesel soot, despite the fact that they number only two million among the state's 30 million registered vehicles.

Because of that situation CARB has set a stringent new reduction of NOx emissions by 90 per cent. The new regulation reduces the current heavy-truck NOx standard from 0.20 grams per brake horsepower hour to 0.050g/bhp-hr from 2024 to 2026 and to 0.020g/bhp-hr in 2027.

In addition, it reduces permissible heavy-truck particulate matter emissions from the current emission standard of 0.01g/bhp-hr to 0.005 for 2024 and subsequent model-year engines.

Importantly, the tighter NOx regulations are based on a new 'low load cycle' (LLC). This measurement takes into account that diesel engines don't always operate at high load factors, particularly in urban situations.

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Also, the ongoing emissions compliance requirement may be extended from the current 435,000 miles to as much as 850,000 to 1,000,000 miles.

American Trucking Associations, the California Trucking Association and the Truck and Engine Manufacturers Association (EMA) immediately objected to the new regulations. However, various truck engine and components makers have been quietly working away at compliance with stricter rules whose introduction they knew was only a matter of time.

An obvious way to comply with the US CTI program is to enhance existing exhaust after-treatment systems and that's just what the Manufacturers of Emission Controls Association (MECA) has done.

MECA's feasibility report was based on engine dynamometer test results and emission models from fully aged after-treatment systems and concludes that engine and after-treatment technologies are available to achieve certification levels within the 2027 timeframe.

However, the solutions considered in the MECA assessment are designed to meet the current full useful life of 435,000 miles, so longer emission durability periods still have to be demonstrated.

MECA believes the lower NOx emission standards will be met without sacrificing fuel economy and increasing carbon dioxide (CO2) emissions. Reductions in fuel consumption will be made possible by such engine efficiency technologies as cylinder deactivation, advanced turbochargers and electrification.

Trucksales has already covered the subject of cylinder deactivation (CDA) as it applies to petrol engines. In these applications a V8 can operate as a four-cylinder at light engine loads, to improve fuel economy and emissions.

In the case of a diesel, cylinder deactivation has the potential to produce similar economy improvements, while maintaining exhaust gas temperatures to ensure correct functioning of emissions after-treatment devices.

CDA may render the more complex MECA post-2027 after-treatment system unnecessary.

Cummins Inc and Tula Technology, Inc have collaborated on a demonstration of diesel Dynamic Skip Fire (dDSF). By using dDSF software to control cylinder deactivation, Cummins and Tula have demonstrated significant reductions in emissions and fuel consumption.

"At Cummins, it's our mission to power a more prosperous world and we do this by helping customers succeed through innovative and dependable products that are good for the customer and the environment," said Lisa Farrell, director of Advanced System Integration, Cummins Inc.

"Our partnership with Cummins has given us the opportunity to expand our DSF technology beyond its success in gasoline engines," said R. Scott Bailey, president and CEO of Tula Technology.

The Cummins-Tula project started in early 2019, using a Cummins X15 Efficiency Series six-cylinder diesel engine. The joint development team modified the engine to use Tula's DSF control algorithms that command combustion or deactivation per cylinder.

In the challenging low-load LLC proposed by CARB, the dDSF technology predicted reductions in tailpipe NOx and CO2. The reduction of tailpipe NOx was achieved primarily by optimised exhaust temperature control, resulting in dramatically improved efficiency of the after-treatment system.

The collaboration is continuing to explore system optimisation and viability to control noise, vibration and harshness in commercial vehicle applications.

If there's one American company that's well-versed in variable cylinder activation it's Jacobs. Best known for its famous 'Jake Brake' engine braking systems, Jacobs' history of variable valve timing hardware makes it a 'natural' for cylinder deactivation.

Jacobs CDA hardware has been developed over the past four years for multiple heavy-duty engine platforms and has been road tested on various vehicles.

Like the Cummins-Tula initiative, the Jacobs CDA technology is said to improve fuel economy by up to 20 per cent at low load conditions, while increasing exhaust temperatures for optimal DPF and Selective Catalytic Reduction (SCR) operation.

Given the fact that Daimler developed electronically controlled cylinder deactivation for some of its big-bore petrol engines and transferred that technology to Chrysler during the long-abandoned Daimler-Chrysler merger, we thought it obvious that the world's number one truck maker would be leading the diesel CDA charge.

Daimler may well be doing just that, but our approach for information was met with a terse: "In principle, for competitive reasons, we do not provide any detailed information on technology aspects."

Although the USA may no longer be perceived as the free world's leader these days, it's one of the most influential markets and a leader in emissions legislation. In the transition to electric vehicles, the 'roadmap' set by CARB's August 2020 legislation sets a time frame for improvements in internal combustion engine developments.

What's clear is that when global markets follow the US lead, we'll see at least some of those technologies make their way Down Under.