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Deactivating Hydraulic Lash Adjuster

In addition to maintaining optimal valvetrain clearances, Eaton Deactivating Hydraulic Lash Adjusters (DHLA) in type II (end pivot overhead camshaft) and type V (pushrod overhead valve) valvetrain architectures can perform cylinder deactivation (CDA) to achieve optimal engine performance and improve fuel economy.  

Deactivating hydraulic lash adjuster benefits

Replacing a standard lift control with a variable valve lifter, increases efficiency and fuel economy.

Fuel economy

Dual mode operation delivers significant improvement in overall fuel efficiency by reducing air pumping losses.

Optimized airflow

Optimizes airflow efficiency with seamless switching from normal to low lift occurring in less than one camshaft revolution.


Maintains centerlines and utilizing existing envelope

Pumping losses in an internal combustion engine

Deactiving hydraulic lash adjusters: How it works

Eaton deactivating hydraulic lash adjuster latched and unlatched

In addition to using Eaton Switching Roller Finger Follower (SRFF) technology, cylinder deactivation (CDA) can also be performed through the use of Eaton Deactivating Hydraulic Lash Adjusters.

Here are the basic principles of Deactivating Hydraulic Lash Adjuster technology:

Base Circle Radius

The Deactivating HLA is pushed up by the lost motion spring to the hard stop. After that the Deactivating HLA covers possible mechanical lashes in the system

Valve Opens

The Oil Control Valve (OCV) is in ‘off’ mode. Oil to the pin is <0.7bar. The cam pushes on the Roller Rocker Arm (RRA) that covers the mech lash on the pin and then transfers the motion to the valve.

Valve Deactivated

The OCV is in ‘on’ mode. Oil pressure to the pin is >1.5bar and the pin moves back. The cam pushes on the RRA that transfers the motion to the HLA because the lost motion spring is weaker than the valve spring.

Cylinder deactivation

While cylinder deactivation has been around for some time, there's more to it than you probably think. Plus, we're using cylinder deactivation in ways you've probably never thought of.

Valvetrain architectures

Type II

In end pivot overhead camshaft architectures, the deactivating HLA is located in the cylinder head. By locating the deactivating element at the pivot of the type II valvetrain, high stiffness can be achieved enabling high engine rpm operation.

Eaton type II deactivating hydraulic lash adjuster system components
Eaton type II deactivating hydraulic lash adjuster system

Type V

In pushrod overhead valve architectures, the deactivating HLA is located in the engine block. By placing the deactivating element in the block a compact low package height solution is obtained.

Components of an overhead valvetrain system with deactivating hydraulic lash adjuster
Eaton type V deactivating hydraulic lash adjuster system