FAQ - Technology

Following are frequent questions about the technologies used to reduce engine emissions:

What is the main challenge in meeting the new standards?

The main challenge in meeting Stage IV standards is achieving the simultaneous reduction of NOx and PM. Decreasing one of them implies an increase in the other. This is because NOx are produced at high temperatures whereas PM occur at low temperatures.

What technology options are available in order to achieve the demanding Stage IV emission limits?

There are several options for achieving reduction of NOx and PM. Each of them has its advantages and also its drawbacks. For example, technologies of in-engine NOx reduction generally lead to higher PM emission levels, while in-engine technologies of PM reduction lead to higher NOx emissions.

What technology will Doosan use to achieve Stage IV emission levels?

The solution that will be provided by Doosan for Excavators, Wheel Loaders & Articulated Dump Trucks is a solution combining EGR+DOC+SCR. This is the case for the Scania Engines (DC09 and DC13) used for our large Excavators, large Wheel Loaders and Articulated Dump Trucks, the Doosan engine (DL06) for mid-size Excavators and Wheel Loaders, and the Perkins engine (1204F) for 14-18t Excavators and the DL200-5 Wheel Loader.

No Diesel Particle Filter (DPF) will be needed. This will provide our products an advantage vs competition using after-treatment technology via DPF.

DC09 and DC13 Scania engines have an XPI common rail fuel injection system of 2400 bar which provides higher performance and margins to meet more stringent emission regulations. Scania Stage IV After-treatment system is ‘DPF-FREE’ thanks to a VGT (Variable Geometry Turbocharger), DOC (Diesel Oxidation Catalyst), SCR (Selective Catalytic Reduction) and further improvement of existing components such as EGR (Exhaust Gas Recirculation).

Which technologies will Doosan use to meet Stage IIIB emission regulations?

Doosan will use different technologies to deliver the best performance and the lowest operating costs for every machine: EGR (Exhaust Gas Recirculation) and SCR (Selective Catalytic Reduction). The best option will be selected based on engineering characteristics and application requirements. In general, EGR technology is suitable for on-site machines requiring multi-task capabilities, such as crawler Excavators, wheeled Excavators and Wheel Loaders below 130 kW. SCR technology is suitable for machines requiring high torque or speed such as the Wheel Loaders above 130 kW and Articulated Dump Trucks.

What is EGR (Exhaust Gas Recirculation)?

Also known as CEGR (Cooled Exhaust Gas Recirculation), this system reduces NOx by recirculating exhaust back into the engine. This dilutes the amount of oxygen in the combustion chamber and lowers the peak combustion temperature.

As a result, NOx formation is reduced but PM is increased. Because of this, Doosan uses EGR in combination with after-treatment systems (DOC and DPF) which are highly effective in reducing PM, as shown below. EGR requires enhanced cooling capacity.


The advantages of EGR include:

  • No change to basic engine technology
  • No special service and maintenance procedures
  • No special operation instructions
  • No need for additives

How does SCR (Selective Catalytic Reduction) work?

SCR applies higher fuel injection pressure and optimises combustion for better fuel economy and response. This decreases PM formation but increases the amount of NOx in the exhaust. The exhaust is treated by injecting a urea solution (AdBlue®) into the exhaust flow. This turns the exhaust into nitrogen and water, which are harmless to the environment.


The advantages of SCR are:

  • • Reduced PM by engine design
  • • Improved fuel efficiency
  • • Improved power, torque and acceleration
  • • Longer service intervals
  • • Compact technology and easy to install (with the same installation for Stage IV)
  • • AdBlue® product well known and widely available
  • • No regeneration required

What is a VGT (Variable Geometry Turbocharger)?

A VGT is a vital part of a Stage IV engine as it gives optimized boost pressure over wide range of RPM so that it generates higher torque and faster response even at low RPM. VGT gets its name from the flow of exhaust gas which is regulated by the sliding nozzle ring and blades (see picture). If the nozzle ring is open, the exhaust gas generates minimal boost pressure where as if the nozzle ring is closed maximum boost pressure is generated. The actuator is electronically controlled by CAN communication for precise movement. The VGT is equipped with a water cooler and a temperature sensor.

What is an Exhaust Brake ?

Main purpose is to bring the DOC up to working temperature in a shorter time. An Exhaust Brake is a device that diminishes the exhaust path from the engine exhaust line, causing the exhaust gases to be restricted in the exhaust manifold, and in the cylinder. This is widely used in (on-road) motor vehicles where additional brake force is required from time to time.

Operation of the Exhaust Brake affects two other devices, EGR and VGT. Once the exhaust brake is activated, the EGR circuit is closed and the VGT is opened which means the cooling system gets warmer (because intake air is not mixed) and more of the exhaust brake pressure can be achieved.

The Exhaust Brake valve is also electronically controlled by the system and deactivates once the operator requires the engine to accelerate.

How does the DOC (Diesel Oxidation Catalyst) system work?

The DOC is a special catalyst that reacts with engine exhaust upon contact. The reaction transforms PM emissions in the exhaust into harmless substances such as water and carbon dioxide. The DOC is used in combination with EGR.

What is a DPF (Diesel Particulate Filter) and what is DPF Regeneration?

The DPF filters engine exhaust to remove PM. It consists of a ceramic wall flow filtration system that separates PM from the exhaust.

Dirty exhaust passes through the filter walls. PM is left behind, and cleaned exhaust exits. Eventually, soot from the filtered engine exhaust will collect on the ceramic walls of the DPF. To keep the DPF operating efficiently, the soot needs to be removed periodically. The semi-automatic process to complete this task is called Regeneration. Regeneration uses heat from the engine exhaust itself to burn the soot off, cleaning out the pores in the ceramic material. The soot is incinerated (destroyed) by the heat, leaving only small amounts of ash behind. The DPF is used in combination with EGR.

What kind of after-treatment technologies does Doosan use to meet Stage IV regulation?

EGR-only engines are not enough on their own to reduce emissions to Stage IV levels. Therefore, Doosan combines them with a selection of after-treatment systems. These include Catalytic Oxidation (DOC) and Selective Catalytic Reduction (SCR) using AdBlue® fluid. These measures are already widely used by car manufacturers. They clean the exhaust produced by the engine or convert it into water, nitrogen and carbon dioxide. The most suitable after-treatment system depends on the engine, and Doosan will tailor the after-treatment to match its systems.

How will Stage IV engines compare to current Doosan engines?

The new generation of Stage IV compliant engines will retain the same high standards of performance, reliability, durability and cost efficiency as the current generation. They will operate with minimal impact on human health and the environment. PM has been reduced by 90 % and NOx by 50 % for Stage IIIB. For Stage IV, both PM and NOx are almost completely eliminated.

Can a Stage IIIA or Stage IIIB compliant engine be upgraded to meet Stage IV emission regulations?

No. The engine design is so different that the cost impact of needed modifications would outweigh the benefit by far. Then, a separate certification of the modified engine would also be required.