09 Aug 2016


It showcases doubled braking power at cruise speeds, 175 kg weight reduction and 3500 Euro lower total cost of ownership. This new Jacobs engine brake is available for heavy-duty drivelines. The HPD two-stroke technology has, for the first time, achieved 819 retarding horsepower (611 kW) setting a new power level and power density record of 63.98 HP/L (47.7 kW/L).

The production-ready Jacobs’ HPD Engine Brake realises one-and-a-half times the braking performance of traditional compression release braking over the engine’s entire operating range and more than two times the braking performance at lower rpm (the same retardation at 1400 rpm as at 2100 rpm previously). Jacobs’ new calibration and revised cam design delivers 2000 Nm of retarding torque at 1300 rpm and beyond and 611 kW power at 2500 rpm in a 13-litre engine, compared to 416 kW at 2100 rpm on the standard, identical engine. This provides large engine displacement retarding power in small and medium displacement diesel and natural gas engines. While delivering revolutionary braking performance, the HPD system is quiet in operation (it had notably lower peak positive power noise than the four-stroke engine braking in NVH drive-by tests), being fully integrated into the customer engine’s overhead design. It can also assist with exhaust after treatment thermal management by preventing the catalyst from cooling during descents.

Jacobs sees a perfect opportunity for the HPD brake in Europe, where there is a premium on retarding power and where Jacobs’ conventional compression release engine braking has been adopted by Daimler, Renault, DAF, Deutz and Volvo.

Earlier this year, Jacobs Vehicle Systems surpassed its previous engine brake retarding world record with the new HPD Engine Brake. At its state-of-the-art engineering laboratory in Connecticut, Jacobs achieved 819 retarding horsepower (611 kW) utilizing a 12.8 litre engine operating at 2,500 rpm engine speed. This sustained power level was reached within the acceptable limits for engine durability and safety using a 900 HP AC motoring dynamometer. This set a new power level and power density record 63.98 HP/L (47.7 kW/L).

Jacobs’ HPD Engine Brake was developed in response to the drive by global engine suppliers to provide higher levels of engine braking performance at lower engine speeds and improve thermal management to match industry trends such as down speeding and downsizing of engines, which are driven by the need for better fuel economy and lower total cost of ownership. Engine brake retarding performance is becoming increasingly important because key strategies for improving fuel efficiency are reducing the natural retarding of the vehicle caused by wind resistance, engine, drive train, and rolling resistance from the tyres.

Jacobs’ HPD Engine Brake transforms the four stroke engine into a two stroke compression device by deactivating the main intake and exhaust valve events and supplementing with two stroke valve events. Whereas a conventional engine brake has one compression release and one brake gas recirculation event per cam rotation, this innovative and patented two-stroke technology achieves two braking events per cam rotation. It is fully variable with controlled boost modulation, which allows the driver to achieve the right balance between retardation, speed and efficiency.

Because Jacobs’ HPD Engine Brake uses standard, proven technology components, it also offers a cost advantage. At a fraction of the price of hydraulic retarder devices it delivers in average a return on investment in six months compared to an average of two-and-a-half years for hydraulic retarder devices.



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