Improving engine performance with Lashless Valvetrains

Commercial vehicles must deliver rock-solid performance, minimize maintenance, and keep operating costs down. One way Cummins is helping customers meet that goal is with lashless valvetrain technology, a system designed to enhance reliability, durability and cut down on service needs.

At the heart of the technology is the Hydraulic Lash Adjuster (HLA), a component that eliminates the need to manually set and adjust valve lash. By keeping valve operation optimized across a wide range of conditions, HLAs enhance both performance and durability.

Cummins Valvetrain Technology (CVT) is leading the way in developing and integrating lashless valvetrains that combine the benefits of HLAs and engine braking. Building on its first HLA-equipped system launched in an off-highway application in 2021, CVT developed the next-generation lashless valvetrain for Cummins B6.7 Octane—engineered for full HLA and engine brake compatibility.

What Is a Hydraulic Lash Adjuster (HLA)?

Hydraulic Lash Adjuster (HLA) technology is designed to automatically maintain optimal valve clearance by compensating for changes in the valvetrain. By eliminating the need for manual lash adjustments during production or service, HLAs offer a major advantage – especially in off-highway, spark ignited and commercial vehicle applications where reliability and ease of maintenance are critical.

Traditionally, however, combining HLAs with engine braking systems has been a challenge. During braking, the additional lash introduced by the brake mechanism can cause an HLA to overextend, risking valve burning or, in severe cases, valve-to-piston contact.

Cummins addresses this issue with lashless valvetrain solutions that apply a reactive load to the HLA during braking events, preventing overextension and ensuring safe, effective engine operation.

Benefits of Hydraulic Lash Adjusters

Cummins’ lashless technologies bring a full range of benefits that drive better performance, lower costs, and greater reliability for off-highway and spark ignited applications.

Enables the use of HLAs with engine braking

Cummins lashless valvetrains allow HLAs to work seamlessly with the Jacobs Engine Brake®, creating a system that offers both performance and simplicity. Technologies such as the Fulcrum Bridge and Spring Bridge provide compatibility across various engine brake types and valvetrain layouts.

Eliminates manual valve lash adjustment

For engines powered by gasoline, natural gas, or hydrogen, eliminating lash adjustment is especially important because these applications traditionally see higher valve seat recession rates. Removing the need to adjust lash improves uptime, simplifies maintenance, and reduces the risk of human error.

Improves cam design and engine efficiency

Using HLAs allows engineers to fine-tune camshaft profiles for better performance, smoother valve seating, and improved fuel efficiency. Hydraulic cam designs offer greater flexibility in how valve events are controlled, helping reduce emissions and fuel use.

Increases uptime and reduces maintenance

By removing the need for lash checks and adjustments in service, lashless valvetrains reduce downtime and cut maintenance costs, which are key factors in improving total cost of ownership (TCO). This is especially valuable for off-highway equipment operating in remote or dirty environments where engine access is limited.

Speeds up engine assembly

Setting valve lash on the assembly line is time-consuming and often a production bottleneck. With HLAs and a Jacobs® lashless solution, this step is no longer required, reducing manufacturing time and cost.

Lowers noise, vibration, and harshness 

HLAs help improve valve seating precision, which reduces the noise and vibration associated with engine operation. For operators of on and off-highway machinery, this means a smoother, quieter experience, which is especially important for long workdays.

Delivers a simple, cost-effective solution

Cummins’ lashless systems provide all these benefits without adding complexity to the engine. Designed to integrate with existing engine platforms, Fulcrum Bridge, Spring Bridge, and other Jacobs Lashless solutions offer a practical and economical path forward.

Why are Hydraulic Lash Adjusters growing in the off-highway space?

Until recently, HLAs were not compatible with commercial vehicle engine braking systems. Braking events introduced main event lash gaps that would cause the HLA to overextend, making reliable performance difficult. 

Cummins changed the game by introducing lashless valvetrain systems that keep the valvetrain stable during braking. This innovation gives engine OEMs a powerful tool for improving performance and reducing emissions while keeping systems simple, safe and engine brake compatible. It also helps meet stricter emissions rules without compromising engine reliability or increasing maintenance burdens.

For end users, the results are clear: lower service costs, reduced noise, vibration, and harshness, and more uptime, all of which contribute to a lower total cost of ownership.

Who offers Hydraulic Lash Adjusters?

Cummins Valvetrain Technologies (CVT) has been at the forefront of HLA-compatible technologies for years. Recognizing the challenges of combining HLAs and engine braking, CVT developed the Fulcrum Bridge and Spring Bridge, which are two proven solutions now deployed across multiple platforms.

These innovations laid the groundwork for Octane, an advanced lashless valvetrain system set to launch with full HLA and engine brake compatibility. Designed with gasoline applications in mind, B6.7 Octane delivers the next step in optimizing engine efficiency, durability, and performance.