What’s happening in diesel engines?

Our recent reports about the rapid electrification of transport fleets in the northern hemisphere have prompted some questions about the future of diesel truck power.

Let’s say, at the outset, that the diesel truck engine will be with us here in Australia for many years to come.

At the IAA show in Germany, although the bulk of exhibits featured electrification technology, there was plenty of innovation on display for future combustion engines.

Europe, the USA, China and Japan are gearing up for electric trucks and buses, but those countries are also ramping up emissions standards for diesel engines.

The aim is to improve the emissions outputs of engines that overseas authorities know will be around well into the 2030s and 2040s. Euro 7 regulations and their international equivalents are expected to take effect in 2027. In Australia, we won’t even officially adopt Euro 6 until 2024, although many of today’s new trucks already meet that requirement.

Leader of the combustion-engine pack at the show in Germany was Cummins, which is already becoming an important supplier of small truck diesels to Daimler and this range is due to expand in early 2023. Trucksales has already reported on the Cummins Agnostic Engine Program and we now have more detail.

“With Cummins all-new X Series platform, we are taking the internal combustion engine to a next generation level,” said Alison Trueblood, Cummins Executive Director – On-highway Business Europe.

“These engines are capable of meeting future ultra-low emission standards, together with a low-to-zero carbon fuel capability, to help put fleets on a lower cost path to decarbonisation.”

The fuel-agnostic architecture of the 15-litre X Series utilises a common base engine with cylinder heads and fuel systems specifically tailored for diesel, carbon-free hydrogen and biogas, with up to 90 percent carbon reduction.

The X15H ratings up to 530hp (395kW) and X15N ratings up to 510hp (380kW), suit these gas-fuelled engines for trucks up to 44-tonnes GCM. The X15 can use either sustainable hydrogenated vegetable oil (HVO) fuel or B100 biodiesel, with ratings up to 650hp (485kW) for heavy-haul tasks.

The Euro 7 Cummins X10 diesel-fuelled engine features the latest evolution of the XPI fuel system, with extra-high pressure injection and an electronic waste-gate turbocharger, enabling fuel savings of up to seven percent compared to equivalent Euro 6 engines, dependent on duty cycle.

Across its 320-450hp (240-335kW) ratings range – with peak torque up to 2300Nm – the X10 meets anticipated Euro 7 ultra-low emission levels, using a Heavy-Duty Compact Cross (HDCC) after-treatment system, developed by Cummins.

HDCC is a modular system, incorporating dual-selective catalytic reduction (SCR), with a twin-dosing system for precision injection of AdBlue.

The X15 diesel also has the Cummins XPI ultra-high pressure fuel injection system and a broad power range of 450-650hp (335-485kW) with up to 3200Nm peak torque. Using B100 biodiesel enables up to a 70 percent reduction in carbon and using HVO renewable fuel achieves up to 90 percent, Cummins claims.

A key design feature of the Cummins X Series platform is a return to double-overhead-camshaft (DOHC) design, for significant advances in combustion and thermal efficiency, as well as a more efficient, integral engine brake.

At the IAA, other US-based engine component makers featured ‘overhead’ valve-actuation innovations, aimed at meeting Euro 7 and its equivalents.

A proved way of reducing emissions in pick-up and delivery fleets is stop-start engine operation. When the truck stops, so does the engine and it restarts when the driver puts his foot back on the accelerator. However, drivers don’t like the cabin vibrations caused by engine ‘stop’ and maintenance people don’t like the wear and tear on starter motors and batteries.

Jacobs Vehicle Systems’ Active Decompression Technology (ADT) is designed to eliminate cabin vibrations and reduce starter wear and battery drain. ADT is, in effect, an automatic decompression device that reduces starter load by 40 percent, Jacobs claims.

When the engine shuts down the ADT keeps the valves open, allowing the engine to coast to a smooth shutdown, without cabin ‘shake’.

The latest evolution of the Jake Brake is the high power density (HPD) design that integrates with the latest cruise control systems and can also operate on natural gas engines.

Offering a claimed double retarding power over traditional engine brakes it’s designed to compete with driveline retarders, saving tare weight and money.

Jacobs’ ‘Lashless’ valve trains are designed to allow the use of hydraulic valve lash adjusters with Jake Brakes. Hydraulic lash adjusters (HLAs) are desirable for improving combustion efficiency and engine performance, but have been incompatible with Jake Brakes, because HLAs extend during braking, making valve to piston contact likely.

Jacobs’ lashless fulcrum bridge and spring bridge eliminates that restriction.

Another Jacobs’ innovation is cylinder deactivation (CDA) that allows a large engine to have the economy of a smaller one by selectively disabling valve operation in certain cylinders, under low-load conditions. (We’ve tested US petrol V8 utes with cylinder deactivation and found that cruising economy was in the 10-12L/100km range.)

In addition to economy advantages, CDA offers faster warm up and preserves after-treatment temperature, of more effective emissions reduction.

CDA is compatible with Jake Brake technology, including HPD engine braking.

Power management company Eaton displayed its Vehicle Group's innovative portfolio of internal combustion solutions for commercial vehicles.

Almost echoing Cummins statement, Traci Melville, senior vice president and general manager, Global Products, Eaton's Vehicle Group, said: "Although the transition to electrification is progressing, OEMs continue to seek improvements in fuel emissions and consumption for internal combustion engines.

“In fact, according to KGP Powertrain Intelligence, there will be more than 30 million new commercial vehicles powered by diesel engines over the next decade.”

Eaton's Variable Valve Actuation (VVA) solutions are said to be adaptable to any valve train architecture, allowing OEM customers to implement one or multiple functions that can significantly reduce carbon dioxide (CO2) and nitrogen oxides (NOx) emissions, with lower fuel use.

Cylinder deactivation keeps selective catalytic reduction (SCR) at optimal temperatures by operating just two or three cylinders rather than all six in light-load conditions. Concurrently, cylinder deactivation also lowers fuel consumption.

Late intake valve closing improves the engine's thermal efficiency, enabling a higher compression ratio, which reduces CO2 emissions and increases exhaust gas temperature that contributes to after-treatment performance.

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Eaton's positive-displacement TVS exhaust gas recirculation (EGR) pump enables the use of a high-efficiency turbo to reduce engine pumping losses and increase fuel economy. The TVS EGR pump is driven by a 48-volt electric motor, making it independent of engine speed and more controllable than pumpless EGR systems, Eaton claims.

Eaton's decompression engine brake technology enhances brake power in the full engine operating range and is compact for easy integration into smaller engines.

Eaton's engine decompression brake is a valve train system with a mechanism to quickly switch between driving and engine braking mode, according to customer requirements and can be integrated into a standard assembly.

As can be seen from the above innovations at the IAA event, diesel engine and component suppliers aren’t deserting the diesel powerplant, which will be the mainstay of many road transport operations for the foreseeable future – particularly in countries like Australia, with high train weights on long-distance linehaul routes.

We’ll keep you updated on all diesel developments as they come to hand, as well as updates on all other future power sources.