The transportation industry is navigating the delicate balance between performance enhancement and sustainability. A pivotal aspect of this journey is the evolution of engine braking and Valvetrain technologies due to the direct link these components have with engine performance and fuel consumption. This article helps explain the latest developments around braking and Valvetrain technologies, and how they are contributing to improved performance while complying with emissions regulations.

Engine braking is a technique that reduces the wear of the foundation brake components and improves vehicle efficiency. It does this by releasing the compressed gas in each cylinder during deceleration at the point where normally fuel would be injected for combustion. This forces the engine to do the work of compressing the intake air, but then the “spring force” of that compressed air is released, so it does not push the piston back down after Top Dead Center (TDC). This can be amplified by changing to a lower gear to increase the engine rpm, and thus the engine becomes a power absorber for the truck, instead of just using the brake pedal to slow down the vehicle.

What is the role of the valvetrain?

Valvetrains are important components of internal combustion engines (ICEs) that play a critical role in managing the engine's breathing process by controlling the flow of air and exhaust into and out of the engine's cylinders. Comprising a series of parts including camshafts, rocker arms, valves, springs and other components, the valvetrain is pivotal in ensuring the engine operates at peak performance.

Optimal valvetrain performance relies on the precise opening and closing of the intake and exhaust valves at the right moments during the engine's cycle. The intake valves open to allow a mixture of air and fuel (or air alone in direct injection engines) into the combustion chamber, while the exhaust valves open to release the combustion gases once the fuel has been consumed.

The camshaft governs the timing of these valve openings and closings, which is critical to the engine's performance, fuel efficiency and emissions. The timing is synchronized with the crankshaft through gears for heavy-duty engines. As the camshaft rotates, its cams (or lobes) push against various components to open and close the valves at precisely timed intervals. The springs then close the valves, sealing the combustion chamber for the compression and power strokes.

Valvetrains can vary in complexity and design, from simple overhead valve configurations to more complex overhead cam and multiple-valve setups. Innovations such as Variable Valve Timing (VVT) and Variable Valve Lift (VVL) systems have further enhanced the functionality of valvetrains, allowing for dynamic adjustment of valve operations to match the engine's operating conditions. This adaptability improves engine performance, increases fuel economy and reduces emissions. This also means that by adapting the latest valvetrain technology, fleets can get on their way to more sustainable operations without sacrificing performance, speed and profitability.

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How do valvetrains work in diesel ICE, hydrogen ICE and natural gas engines?

Valvetrains in ICE and natural gas engines, play a pivotal role in controlling the entry and exit of gases in the engine's cylinders. Despite the similarities in how they work, the nuances in fuel and combustion properties mean that each fuel type needs a different approach for valvetrain designs across these engine types.

In diesel ICEs, the valvetrain operates under high-pressure conditions due to the diesel fuel's high compression ignition nature. The system is designed for durability and precision to handle the engine's operation without spark plugs. The timing and lift of the valves must be meticulously managed to optimize the air-fuel mixture's efficiency, ensuring complete combustion and minimizing emissions.

Hydrogen ICE presents unique challenges, primarily due to hydrogen's high combustibility and fast flame speed. Valvetrains in these engines are adapted to manage faster combustion cycles, requiring precise timing to prevent pre-ignition or backfires. The material selection is also critical to withstand hydrogen's low lubricity and high combustion temperatures.

For natural gas engines, valvetrains are tailored to accommodate the fuel's lower energy density compared to diesel. This necessitates efficient air-fuel mixing for complete combustion, achieved through precise valve timing and lift. Additionally, natural gas is a cleaner-burning fuel that allows for valvetrain components to be designed with considerations for reduced soot and contaminant exposure, helping to increase the lifespan of these parts.

Across all of these engine technologies, the evolution of valvetrain technology continues to focus on enhancing performance, reducing emissions and adapting to the unique requirements of each fuel type.

Significant innovations in valvetrain technologies emissions reductions

Engine braking, traditionally associated with the compression-release method, has undergone a transformative change by altering the timing of valve openings and closings. Cummins Inc’s innovative approach applies Jake Brake® technology to the exhaust valve, which  enhances engine braking efficiency. Cummins has also pioneered heavy-duty Cylinder Deactivation Technology (CDA), a revolutionary step in engine design aimed at optimizing fuel economy and reducing emissions. This method involves disconnecting engine valves from the cam, so they do not open at all, eliminating fueling for that cylinder and thus, allowing for a portion of the cylinders to be shut off under certain conditions. For instance, during low load or idle times, deactivating a six-cylinder engine's valves forces the remaining cylinders to operate under higher loads, thereby burning fuel at a higher temperature. This increased combustion temperature is crucial for the effective operation of diesel aftertreatment systems, (ATS), such as selective catalytic reduction (SCR) units, which chemically react with nitrogen oxide emissions (NOx) to render them inert. Maintaining the ATS at optimal temperatures (above two hundred degrees Celsius) ensures efficient reactions and the reduction of pollutants, a key goal during idle or low-load operations where heat generation is typically insufficient.

Addressing concerns about the reliability of these advanced valvetrain technologies, extensive testing and real-world applications have demonstrated their dependability. Cummins Inc’s commitment to integrating these systems seamlessly into engine designs from the outset, ensures not only their reliability but also their cost-effectiveness.

Gone are the days when engine brakes were an afterthought, added after the development phase. Today, they are an integral part of the engine design process, calibrated to each engine for optimal performance. This integrated approach to valvetrain technology development represents a shift towards more efficient and cleaner engines that meet the demands of modern transportation without compromising on reliability or affordability.

Through continuous innovation, engine braking and valvetrain technology have become more adaptable, efficient and environmentally friendly. This evolution underscores the importance of these components in shaping the future of transportation, ensuring engines not only meet, but exceed the environmental standards of tomorrow, marking a significant milestone in our journey towards a cleaner, more sustainable future. As the industry moves towards a more sustainable future, Cummins' innovations in engine technology continue to set benchmarks for performance, safety, and environmental stewardship.