The first to market application of Cummins Valvetrain Technologies’ High Power Density® (HPD) engine brake will be on Cummins’ new X10 engine destined for heavy   and medium-duty vehicles , serving vocational, regional haul or transit bus fleet customers. 

The X10 engine is part of Cummins’ HELM™ fuel-agnostic engine lineup, where it replaces both the L9 and the X12 engines. 

The 1.5-Stroke HPD engine brake, as specified by Cummins for the X10, provides small and medium displacement engines with large engine displacement retarding power, generating up to 40 percent higher levels of supplemental braking force than traditional compression release braking at high engine speeds, and improvements of up to 100 percent at lower RPM cruising speeds. This supports the commercial vehicle industry’s pursuit of better fuel economy and lower total cost of ownership. 

A conventional engine brake has one compression release (CR) and one brake gas recirculation (BGR) event for each of the engine’s cam rotations. With 1.5-Stroke HPD, cylinder de-activation (CDA) mechanisms are used to eliminate the main exhaust valve events, allowing two CR events per cam rotation. 

A standard intake charge event is used to power the first CR event, however, for the second CR event, the power is achieved through the recirculation of exhaust manifold gases, without drawing air from the intake.

Two HPD engine brakes, a 3-cylinder and 6-cylinder version, will be offered on the X10 to provide coverage for customers formerly specifying Cummins L9 (medium-duty) and X12 (heavy duty) engines, respectively.  The advanced brake offers up to 320 hp at 2300 rpm for the 3-cylinder option, and up to 475 hp at 2300 rpm for the 6-cylinder option.

RaNae Isaak, Program Leader of the X10 at Cummins, said, “The HPD engine brake is both a unique and ideal braking solution for the wide displacement coverage of the new X10 engine, as well as the variety of duty cycles to be served. Feedback from both OEM and end-user customers who have test-driven the new X10 with the HPD engine brake attest to its ability to offer the braking power of up to a 13-liter truck, via a 10-liter displacement engine. In fact, many comment that the HPD engine brake is the most powerful braking solution in a vehicle they have ever driven.”  

HPD is part of Cummins Valvetrain Technologies’ common modular design frame, meaning other valvetrain technologies can be integrated, or removed, according to local market requirements. It is being developed in six other engine programs. 

“Punching above its weight class, the HPD engine brake is an attractive, differentiating proposition for both engine and vehicle designers. It’s a perfect match for the Cummins X10 engine because of the diverse number of applications, many that need high braking performance. With the exhaust side of Cummins’ CDA already integrated as part of HPD, future applications will have a built-in bridge to the specification of full CDA for customer markets that demand a fuel-saving and emissions-reducing technology. All that needs to be added are additional control solenoids and collapsing intake mechanisms to an already protected framework.” 

Two-Stroke and 1.5-Stroke HPD were announced in 2016 and 2018, respectively, by Jacobs Vehicle Systems, which was acquired by Cummins in 2022.