## 3 Results and Discussion
### HEV Simulations with GCI Engine Test Results
#### 3.2.2. CN25 Engine with Different Hybrid Configurations (Serial, Parallel, Serial/Parallel)  
The CN25 fuel engine experiments were performed on an SCE engine test cell, and the engine data used for the simulation was the full engine map that was created by the GT-Power engine simulation results, which were based on the GCI engine test results from Aramco GCI project. The vehicle that was considered in this assessment is a typical medium-sized C-segment passenger car. The type of engine is a 1.8 L, 4-value CI engine with a 15:1 compression ratio. Emissions were not considered in this engine approach because the engine operating in the hybridization area might produce very low engine out emissions. Figure 8 shows the results for the speed, torque, power, and fuel consumption of the CN25 engine from the HEV simulation. The assessment of electric components used a 2.0 kWh battery, an 80 kW of EM, and a 50 kW generator in different full hybrid configurations. The main idea was to select a hybrid configuration through the comparison of the results for CN25 vehicles with different hybrid configurations. As shown in the figure, the power sharing duration between the engine and electric devices are longer in case of a parallel hybrid in WLTC. In hybrids with parallel drivetrains, the engine, and EM can provide mechanical power simultaneously. In the case of the serial hybrid, it only received mechanical power from the EM, which is run by either a battery or an engine-powered generator. It is for this reason that the electric driving mode is mostly utilized at low vehicle speeds to minimize fuel consumption, and the status of the ICE is determined by the state of charge (SOC) values of the battery. In case of a non-plug-in hybrid (non-PHEV), the serial/parallel configuration has some fuel consumption potential compared to other hybrid configurations. In spite of the system complexity of the serial/parallel hybrid, this hybrid has more flexibility for the energy management for the SOC and fuel consumption. Understanding the advantages of the gearbox (more variants with different gearbox location and different number of gears) and guiding the proposition of better topology for the complex system are the main reasons for the improvements to the serial/parallel hybrid. Figure 7: Engine-out and tailpipe emissions by hybridization coverage of the operating points of CN35 engine on cold WLTC with 48 V P2 Parallel HEV configuration. Figure 9 shows the coverage of the engine operating points of WLTC after the hybridization (serial/parallel configuration). In general, such an engine possesses a peak effective efficiency of approximately 38%. It is obvious that the WLTC operating point distribution is in the optimum efficiency range for this engine. Therefore, the mean engine efficiency during the cycle reaches a value of 31.9%. This result is based on warm measured engine maps. The CN25 engine possesses a high peak efficiency of approximately 42% over a wide area of the engine map. However, the high engine efficiency area is located at high engine loads. The benefit of CO2 from the high engine efficiency will not be as high, as the engine operates at low engine efficiencies during WLTC when it is not hybridized. A CN25 engine cannot benefit from its high peak efficiency to a full extent. The operation points are shifted to higher loads and hence higher engine efficiencies when hybridized. As a result, the mean engine efficiency during WLTC increases to 38%. Consequently, the CN25 engine is the most suitable for hybridization. The CN25 engine achieves a fuel consumption improvement of about 9% compared to the Euro 6d-based engine. An additional benefit of 28.1% can be realized when the vehicle offers the discussed hybridization and when the charge sustain mode is considered. In total, a reduction of 37% can be seen based on weighted CO2 emissions according to the WLTC certification. Figure 8: Speed, torque, power, and fuel consumption of CN25 engine with different hybrid configurations (WLTC).