As you may be aware, Volvo’s 2024 VNL truck brings together driver comfort, maintenance simplicity, improved fuel efficiency, and better fleet operating performance. The truck introduces significant enhancements in these aspects. Notably, it boasts enhanced aerodynamics with a distinctive wedge shape, visible from above, and features a sophisticated duct system that optimizes airflow through the engine compartment for cooling while reducing resistance.
Internally, the truck incorporates advancements in its electrical system and engine mechanics. The most notable change is the adoption of a 24-volt electrical system, particularly beneficial for VNLs equipped with sleeper cabs. This enables the integration of a groundbreaking battery-powered parking cooler, allowing drivers to enjoy silent and comfortable sleep for up to eight hours without needing to idle the engine.
The shift to a 24-volt system reduces current demand across various components, including wiring harnesses, the parking AC compressor, starter, and alternator. This results in increased efficiency and reduced heat generation, particularly evident in the sleeper AC compressor and starter. The reduced amperage facilitates smoother operation and lessens heat build-up during extended use.
The truck’s nearly silent overnight sleeper air conditioning is achieved through a chassis-mounted electrical compressor and two electric condenser fans positioned in front of the radiator. Additionally, Volvo addresses concerns about battery replacement by utilizing standard 12-volt batteries wired in series to provide 24-volt power, eliminating the need for rare 24-volt batteries.
In the realm of battery systems, Duane Tegels explains that day cabs will come equipped with flooded lead-acid batteries, while sleepers will feature AGM (absorbed glass mat) batteries as standard. This choice ensures excellent energy storage capacity, especially for auxiliary power needs. AGM batteries are designed for deep-cycle use, allowing them to be discharged down to 50% of their capacity without significant wear, while still retaining sufficient power for engine startup.
Moreover, an optional ultra-capacitor starting system can supplement cranking power when needed. To safeguard battery health during sleeper air conditioning operation, a battery protection system kicks in: if excessive power draw causes voltage levels to drop dangerously low, the system will start the diesel engine to recharge the batteries, preventing premature battery wear or potential starting issues.
Volvo offers a range of battery and 24-volt alternator configurations, including the option for up to six AGM batteries. Alternators are available in both brush-type and brushless designs, with capacities reaching up to 160 amps. Despite the higher voltage, the 24-volt alternators are designed to fit seamlessly into the existing serpentine belt system, requiring no additional torque for operation. Dealers will stock 24-volt alternators and starters in preparation for the April production launch.
For on-road cooling needs, standard AC systems with belt-driven compressors will cool both the cab and sleeper compartments. The engine cooling system will also utilize a belt-driven fan. Despite the shift to a 24-volt system, compatibility with the 12-volt infrastructure remains intact, ensuring smooth integration with existing setups.
“All vehicle lighting is now 24-volt LED-based, but there are still 12-volt components in the trucks,” Tegels said. “For those specific components, voltage converters provide the required 12-volt supply. All DC power supplies inside the cab are either 12-volt or USB-C. If the truck is equipped with shore power or an inverter, 120V AC power is also provided within the sleeper. We also secure 12-volt interfaces for body builders and trailer connections.”
The 2024 VNL boasts numerous powertrain enhancements that will delight both drivers and fleet managers alike. Significant improvements have been made to maximize power and torque output. Last year’s top rating of 455 horsepower with 1,850 pound-feet of torque has been surpassed by two new ratings: a 500 horsepower, 1,850 pound-feet torque rating, and a 500 horsepower, 1,950 pound-feet torque rating.
Volvo engineers have devised a clever solution to minimize piston side-thrust and friction by elongating the engine’s connecting rods. This was achieved by redesigning the piston to be shorter with the pin mounted closer to the crown. Additionally, the crown of the piston now features seven waves instead of six, necessitating the use of a 7-hole injector rather than the previous 6-hole design. The injector also incorporates a smaller needle and valve seat at the bottom, resulting in quicker response times and more consistent atomization, particularly beneficial during cold starts.
According to Tegels, the adoption of seven-wave injectors marks a significant milestone, enabling finer fuel spray patterns and precise control over the fuel injection process. These advancements contribute to improved engine performance, efficiency, and reliability.
“This refinement ultimately fosters an enhanced fuel-to-air mixture, promoting a more complete combustion process,” he explained. “This optimized combustion results in a higher combustion efficiency, leading to the combustion of a greater proportion of fuel and a notable reduction in the formation of hydrocarbons that contribute to soot.”
This claim finds support in the research conducted by renowned scientist Dr. Dennis Siebers and his team at Sandia Laboratories. Their investigation into engine combustion dynamics unveiled a significant advantage of advanced diesel injection systems: the utilization of smaller nozzle holes, leading to the production of finer, smaller-diameter sprays—a hallmark of the 7-hole injector design. These diminutive sprays exhibit superior air intake characteristics, effectively reducing soot formation resulting from inadequate air supply. Tegels emphasizes that the additional pockets formed by the increased number of waves in the injector also enhance turbulence within the combustion chamber.
Further enhancements are achieved through the implementation of a smaller-diameter turbocharger and turbo-compounding turbine, facilitating faster spooling. Improved insulation of these components retains heat within the system, bolstering overall performance.
These combustion improvements also translate into reduced heat exposure for the piston crown, resulting in more uniform heating patterns. This reduction in heat stress not only enables the increase in power and torque but also contributes to an overall fuel economy improvement of up to 10%, while simultaneously reducing strain on the engine oil.
In addition, the new powertrain introduces a 30% faster shifting mechanism, noticeable during test drives and appreciated by drivers for its enhanced acceleration. This achievement is realized through a reduction in clutch throw from 4 mm to 2 mm and the implementation of a more potent countershaft brake, facilitating quicker synchronization of gear speeds and engagement of subsequent gears.
Moreover, the enhanced engine brake aids in achieving the appropriate engine speed during shifts, minimizing turbo lag and ensuring swifter engine response post-shift, consequently enhancing overall acceleration and fuel efficiency. The adoption of a fuel economy-focused I-torque specification includes a rapid 2.15:1 rear axle ratio, inspired by insights from industry expert Joel Morrow. This setup, utilizing the D13 TC powerplant, operates at a mere 960 rpm at 65 mph on level terrain, harnessing the engine’s torque peak at 900 rpm for optimal performance. Complementing this setup is a 13-speed transmission, featuring a crawler gear for improved startability and maneuverability, despite the ultra-fast axle ratio.
