“Tough Gear”and “High Quality”for New X-TRAIL - 2. “VC-TURBO”and“e-POWER”System4. Overview of X-TRAIL-dedicated e-POWER Fig. 3 New e-POWER systemTable 1 Specifications of the new e-POWER systemsystem5. Overwhelmingly superior performance5.1.1 Engine operating frequencyFig. 4 VC-TURBO compression map5.1 Quietnesshigh-performance requirements. Along with global expansion, the need to respond to towing requirements and high-speed driving requirements were also added.Fig. 3 illustrates the newly developed e-POWER system and Table 1 summarizes its main specifications. Compared to the existing 2nd-generation e-POWER system, the drive motor is enlarged, the displacement of the power generation engine is increased from 1.2 L to 1.5 L with a supercharger, and the VC-TURBO engine is equipped with a variable compression ratio mechanism. Further, the 4WD model is added to the lineup.The existing e-POWER system is based on fixed-point engine operation, and therefore, the fuel consumption rate during the fixed-point operation considerably affects the fuel efficiency of the vehicle. This trade-off between the fuel efficiency and the output performance needs to be eliminated to increase the engine output while maintaining fuel efficiency during fixed-point operation. To this end, the new e-POWER system employs a VC-TURBO engine to achieve high output with the compression ratio set to low at the output point, while maintaining high fuel efficiency by setting a high compression ratio during fixed-point operation. Fig. 4 shows the compression ratio map and engine operating point frequency of the VC-TURBO engine.12A special exhaust system is specifically developed for the engine operating point unique to the e-POWER system, which does not utilize engine speeds below 1500 rpm. The exhaust system reciprocates the tube in the rear muffler to reduce resonance and exhaust noise. In addition, an optimal bypass route is set to generate low exhaust pressure for ensuring sufficient engine output.For the brake system, an electric control brake unit was incorporated in the e-POWER system for the first time; this resulted in improved quietness through collaborative control with the e-POWER system. In the previous e-POWER system, there was a need to start the engine to generate negative pressure when braking. However, the use of an electric brake eliminates this need, which reduces the frequency of starting the engine. Further, the previous e-POWER system generated a deceleration G through a regeneration system when driving downhill; however, after the vehicle is fully charged, it was necessary to maintain the deceleration G while rotating the engine at high speed and discharging the regenerative energy. The new X-TRAIL is equipped with an electric controlled brake unit that stops regeneration after a full charge and activates the electric brake to ensure deceleration G, which helps suppress an increase in engine speed and improves quietness.The overwhelmingly superior quietness, acceleration performance, drivability, fuel economy, and exhaust performance provided by the X-TRAIL e-POWER system are described below.The C-segment SUVs are heavier than compact cars, and therefore, the former requires more energy when starting and accelerating compared to that for the latter. Thus, the engine operating range expands if conventional energy management system is used, which can lead to an increase in the engine start frequency and a loss of
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