Doosan's upgraded DX350LC excavator is powered by a 281-hp (209-kW), six-cylinder DL08K water-cooled diesel engine that has been optimized for use with a cooled exhaust gas recirculation (EGR) system, a diesel oxidation catalyst (DOC), and a diesel particulate filter (DPF). The turbocharged 466-in³ engine features direct fuel injection, electronic control, and four valves per cylinder.
The engine's high-pressure common-rail (HPCR) system increases the efficiency of fuel delivery by increasing the pressure to 26,100 psi (1800 bar). The increased pressure allows the injector to inject a finer mist into the engine, which results in a more efficient combustion as required by the lower combustion chamber temperature due to the cooled EGR system.
Cooling system upgrades include two variable-speed hydraulic fans, which allow the engine and oil cooling systems to be controlled independently for improved fuel efficiency and a quieter operator environment. The new cooling system on average has a 10 to 15% greater cooling capacity.
The improvements in engine horsepower and torque, coupled with the 6% increased maximum pressure from the main control valve, mean increases in various workgroup functions.
Doosan says the swing torque increased by approximately 8 to 11%, which allows the excavator to swing uphill more easily, as well as improve backfilling trenches. This leads to decreased time per foot of trench, improving productivity. Digging force has increased approximately 5%, which allows for more power in harsh digging conditions for decreased cycle times and improved production in trenching applications.
Lifting capacity increased by approximately 2%, providing improved power out of the trench, allowing the machine to lift and place more material with each cycle. The boom-up speed improved by approximately 6%, which allows for more work to be completed faster, increased cycle times, improved truck loading time, and more material moved per hour.
A variable geometry turbocharger (VGT) is utilized to increase boost pressure at lower engine rpm. Controlled by the ECU, the VGT varies the amount of boost supplied to the engine to optimize combustion over the entire rpm range. The VGT also allows the engine to generate a greater amount of torque in a wider band in the rpm range, increasing engine performance at lower engine rpm. This improves machine performance in the standard and economy power modes while saving fuel.
The new closed center main control valve with electrohydraulic pump control, exclusive to the DX350LC, allows the ECU to maximize engine power. Doosan claims this leads to a 20% increase in efficiency of the main control valve for improved fuel economy. Workgroup performance increased approximately 10% compared to the Tier 3 DX350LC model. Smoother control and more accurate placement of materials is a result of the operator’s ability to control the machine with more precise movement.
Additionally, the new boom float option allows the boom of the excavator to “float” up or down, allowing the operator to focus more on the task while decreasing the machine workload and increasing efficiency. The float mode allows the boom to move freely up and down without hydraulic flow. The breaker mode allows the boom to freely move down, only without hydraulic flow. A temporary reset button allows the ability to momentarily disengage the float, allowing hydraulic flow to activate the boom.
Doosan looked for improvements to operator comfort with further enhancements to the ROPS (roll-over protective structure) cabin. Both a seat height lever and tilting function for the seat cushion were added to the seat to allow the operator to find an optimum seating position. The cabin mounting mechanism has been improved with a thickened dampening plate, and a coil spring has been added to reduce cabin vibration 20%, for longer days with less fatigue.
The door window position slider now locks in various positions, preventing it from moving from its intended location. Both front and rear glass windows are also adjustable. The door space of the cab has increased by 1.8 in (46 mm), allowing the operator to get in and out more easily. The cabin size has increased 6.1%, providing more headroom. The joystick angle has been reduced from 25° to 19° to provide a more ergonomic profile and decrease interference with operator’s legs.