Skip navigation

Breaking news: Combining hydraulics and diesel engine controls makes for higher dynamics at lower speeds

Edited by Mary C. Gannon

Intelligent integration of hydraulics and diesel engine control retains the dynamics of machine functions even with Tier 4 final engines and enables a fuel-saving reduction of rpm's without sacrificing overall performance.

As more equipment builders work to meet the requirements set by TIER 4 emissions regulations that will take effect in 2014, the chance of significantly poorer load response in diesel engines is becoming greater. In addition, to consume less fuel, manufacturers of excavators, telehandlers, and other mobile work equipment are reducing engine speeds. As a result, most control devices used for the drive and working hydraulics cannot compensate for this "sluggishness" — creating a potential risk for lower productivity.

Now comes news that Rexroth has developed a system that provides high dynamic response of the travel drive and implement hydraulics on mobile work equipment even at reduced diesel engine speeds and for TIER 4 final engines. The company’s electronic BODAS system solution, "Diesel Hydraulic Control (DHC),” was developed with the diesel engine specialists from Bosch, the world's largest automotive supplier. Rexroth says the engine management system reduces diesel fuel consumption by up to 20%.

DHC retains the response of the travel drive and implement hydraulics even under conditions of diminished load response and lower engine speeds. DHC changes the traditional function sequence and lets the diesel engine know of expected load requirements. This is accomplished using matched controllers from Bosch for engine management and from Rexroth for the travel drive and implement hydraulics, using a common special map. This DHC system map represents the vehicle-specific relationships between speed in rpm, efficiency and torque.

Diesel Hydraulic Control continuously determines the demands of the travel drive and implements hydraulics, using this information to dynamically calculate the optimal operating points for the diesel engine and hydraulic components by means of the DHC system map. For example, the joystick for the implement hydraulics transmits pending work requirements directly to the DHC, which passes this requirement to the diesel ECU. This gives the engine time to prepare for the imminent mechanical load. At the same time DHC makes it possible to operate the equipment at the accustomed dynamic response levels in spite of lower engine speeds, thereby saving fuel.

Because DHC means that the diesel engine only provides as much power as the machine actually needs at any given moment, diesel fuel consumption is reduced compared with current figures. Fuel savings of up to 20% as measured in real-life testing will reduce the total cost of ownership for operators with no sacrifice in dynamic response of the travel drive and implement hydraulics.

Visit for more details.