## 2 Proposed System  
In order to stablish the basement for this study, it was necessary to choose the optimal combination of elements that suited our requirements. In first place, it was clear that strict values of NOx emission form standard Euro VI would be a good starting point. This pollution limitation is a great challenge for all sorts of transport vehicles, especially for heavy duty vehicles manufacturers. Man Truck & Bus A.G. (Munich, Germany) is an example of how the use of sophisticated ECU software, combined with catalytic chemical reactions, can obtain NOx ppm values below Euro VI limits. The vehicle used in this article is a Euro VI certified HDV from MAN, model TGX 18.480 Efficient Line 2. The vehicle disposition and the main data acquired can be shown in Figure 1.  
The system proposed is based on the existing aftertreatment system (ATS) retrofitted by an EGH. The EGH, shown in Figure 2, was located upstream of the ATS and, in essence, it is a 12 kW electric coil temperature controlled by a PID system. To simplify the test, the EGH was not powered by the vehicle's battery, but it was connected directly to the electrical network. The control unit adjusted the power injected to the EGH according to the temperature set point. Apart from the data acquisition shown in Figure 1, it is also necessary to gather other important parameters such as EGH inlet and outlet temperatures, \(T_{B\_ECH}\) and  
Figure 1: Efficient Line engine and transmission with ECU and rolling bench data parameters.  
\(T_{A\_EGH}\) respectively and the electrical power consumption of the EGH \(P_{EGH}=V_{EGH}\cdot I_{EGH}\). The EGH coupled to the standard exhaust system can be seen in Figure 3.  
As seen in Figure 3, EGH (number 1) has been located downwards the turbochargers, just before the standard ATS. The next element we find is the diesel exhaust fluid (DEF) unit composed by a tank, a supply module, and a dosing module (number 2). The vehicle tested in this experiment uses AdBlue for NOx abatement. The ECU is the responsible of the AdBlue parameters, which is never injected into the system until the exhaust gas temperature exceeds 180 \({}^{\circ}\)C. Inlet gas temperature and NOx content are read by the dosing unit to adjust the exact dose of AdBlue required to meet the EURO VI standard.  
Figure 3: Scheme of the proposed system retrofitted in the tested vehicle with an ATEG representation.  
Figure 2: Scheme of the EGH installed upstream the ATS and its data acquisition.  
Next component we find is a closed unit composed by a selective catalytic converter (SCR) and a continuous regenerating trap (CRT). At this point a mix of AdBlue and exhaust gases enter into the SCR (number 3). Inside this device a catalytic reaction is produced to convert NOx into diatomic nitrogen (N\({}_{2}\)), and water (H\({}_{2}\)O). Carbon dioxide (CO\({}_{2}\)) is a subproduct of this reduction when urea is used as DEF. Finally, it is necessary to eliminate NH\({}_{3}\) produced by the reaction between AdBlue and NOx. Using an ammonia catalyst, included into SCR system, NH\({}_{3}\) is converted into nitrogen and water.  
Afterwards the SCR and within the same package the CRT (number 4) is divided into a diesel oxidation catalyst (DOC) and a diesel particle filter (DPF). The DOC is the responsible of CO and THC oxidation while the DPF is used to capture the unburned particles. Soot trapped in the DPF walls is burned when an excessive backpressure is reached. The same closed unit is the standard exhaust outlet where NOx sensor is coupled to acquire the vehicle emissions \(NOx_{EGH}\).  
Regarding Figure 3, there is a representation of an ATEG (number 5) to demonstrate which is going to be its suitable location, just at the end of the standard ATS. Its outlet manifold would be the collector of exhaust fumes where the NOx sensor is attached in this figure. This ATEG is a conceptual approach of size, location and design. The tested vehicle has its NOx sensor connected at the exhaust outlet, underneath the SCR + CRT unit.