Acura RLX Sport Hybrid Powertrain Explanation

    Recently, Acura released the RLX Sport Hybrid SH-AWD sports hybrid model. The new car not only improves the sports handling performance but also takes fuel saving and environmental protection into consideration. The car was first launched at the Los Angeles Auto Show on November 20, 2013. As a high-end model of Acura, a luxury brand under Honda, the Acura RLX Sport Hybrid SH-AWD has a power output of up to 377 horsepower (281 kilowatts), and its fuel efficiency on urban roads can reach 28 miles per gallon, and its fuel efficiency on highways can reach 32 miles per gallon. This fuel efficiency data has also been certified by the US Environmental Protection Agency. The new Acura RLX Sport Hybrid SH-AWD model does not significantly reduce the overall weight of the vehicle. The main highlight of this time is the Super-Handling All Wheel Drive (SH-AWD) system equipped with the vehicle and the electric motor that can supply power more accurately. The car not only improves the sports handling performance, but also ensures good fuel economy.

Twin motor unit on rear axle

    The new Acura RLX Sport Hybrid SH-AWD is equipped with three electric motors: two for the rear wheels and one for the front wheels. Each rear wheel is equipped with an electric motor with a maximum power of 27 kilowatts and an output torque of 54 pound-feet (73 Newton-meters); the electric motor equipped on the front wheel has a power of 35 kilowatts and an output torque of 109 pound-feet (148 Newton-meters). At the same time, it is also equipped with a 3.5-liter V6 engine with an output power of 310 horsepower (231 kilowatts). Since the electric motor and the traditional fuel engine have different speeds when they reach maximum output power and maximum output torque, the three electric motors and the traditional fuel engine can achieve a maximum output power of 377 horsepower (281 kilowatts) at 6000 rpm and a maximum output torque of 377 pound-feet (511 Newton-meters) at 4600 rpm.

    The new Acura RLX Sport Hybrid SH-AWD uses a 3.5-liter V6 direct injection engine, Honda variable cylinder management system, i-VTEC engine timing and lift control system, two-stage oil pressure control system and engine fuel heater and other advanced technologies. As a full-function hybrid model, the new Acura RLX Sport Hybrid SH-AWD is equipped with an electric air conditioner, so that the heat in the car will not be lost even when the vehicle is idling. At the same time, the engine active management system is used in conjunction with the intake valve delay system to ensure that the vehicle can be restarted smoothly. During this test drive, the driver can clearly feel the smoothness of the vehicle restart.

    The new Acura RLX Sport Hybrid SH-AWD can be driven in pure electric mode. In pure electric mode, the two electric motors connected to the rear wheels can fully drive the vehicle, and the energy source is the on-board lithium-ion battery pack. Driven by the rear-wheel motor, the vehicle can start and accelerate quickly, a mode called electric acceleration (EV launch). At the same time, the vehicle can cruise at a maximum speed of 50 miles per hour (80 kilometers per hour) under rear-wheel drive, a mode called electric cruise (EV cruise). The front-wheel motor can not only accelerate the vehicle slowly, but also collect energy to charge the on-board battery pack when the engine drives the vehicle or the vehicle cruises at high speed. When the vehicle accelerates at full speed, the three electric motors simultaneously assist the engine to provide energy for the vehicle.

Braking energy recovery

    When the new Acura RLX Sport Hybrid SH-AWD vehicle decelerates, the engine is disconnected from the transmission, and all three motors act as generators to collect energy to charge the onboard battery pack. In slippery driving conditions, the engine and rear-wheel motors form the vehicle's four-wheel drive system. Since the vehicle is basically not in an accelerating state at this time, the front-wheel motor is in a stopped state. If the onboard battery pack is too low, the vehicle is driven by the engine, and the motor is in a generator state to charge the onboard battery pack.

    The new Acura RLX Sport Hybrid SH-AWD is not a plug-in hybrid model, so its on-board battery pack has a small capacity of only 1.3 kWh and its operating voltage is 260 volts. At the same time, the new Acura RLX Sport Hybrid SH-AWD is also equipped with an Intelligent Power Control Unit (IPU) behind its rear seat. Compared with the 15.3 cubic feet (433 liters) trunk volume of the Acura RLX Sport non-hybrid model, the trunk volume of the new Acura RLX Sport Hybrid SH-AWD is 12 cubic feet (340 liters). Therefore, the space occupied by its on-board battery pack is quite small. At the same time, the motor control system and power control unit of the new Acura RLX Sport Hybrid SH-AWD replace the position of the underbody drive shaft in traditional non-hybrid models.

    The new Acura RLX Sport Hybrid SH-AWD front-wheel electric motor is connected by a seven-speed planetary gear set and a six-speed wet dual-clutch transmission (DCT). The transmission sequence is electric motor, seven-speed planetary gear set, and six-speed wet dual-clutch transmission.

    Yasuo Kitami, assistant director of Acura's hybrid system major project, said the mechanical response time of the new Acura RLX Sport Hybrid SH-AWD hybrid system is 10 milliseconds. The traditional non-hybrid Acura RLX Sport SH-AWD model uses an electromechanical clutch pack to distribute torque to the rear wheels. The new hybrid model is equipped with an electric motor for each rear wheel, so that each motor can independently control the corresponding rear wheel, which can distribute the output torque more accurately. The rear wheel motor uses a dual pinion system and is equipped with a dual motor housing. The front wheel power drive system can set the target torque value for the rear wheel motor through electronic equipment based on the vehicle's steering angle size and change rate, yaw moment, lateral acceleration and vehicle speed.

    When turning, the outer tires of the vehicle rotate faster than the inner tires. Conventional non-hybrid Acura RLX Sport SH-AWD models can provide positive torque to push the vehicle to turn. When encountering a sharp turn, the new Acura RLX Sport Hybrid SH-AWD hybrid model reduces the speed of the inner tire, thus generating a negative torque, and the inner motor enters the engine mode, so the outer tire can also get more output torque.

Smooth transition between different modes

    Yasuo Kitami said that although the new Acura RLX Sport Hybrid SH-AWD is equipped with three electric motors, which can control electronic equipment more accurately and flexibly, the difficulty lies in whether the vehicle can smoothly transition between different working modes. For example, the vehicle transitions from pure electric acceleration to engine start and then drives the front wheels. In addition, the transition to all-wheel drive when the road surface changes. After the test drive, the new Acura RLX Sport Hybrid SH-AWD can complete the transition very smoothly in different working modes.

    Honda has been working on a custom version of its front body structure with Advanced Compatibility Engineering. The goal is to achieve good results in the Insurance Institute for Highway Safety narrow offset obstacle test. As the latest model, Acura hopes that the new Acura RLX will achieve good results in this test and four other tests (vehicle front impact test, side impact test, front and rear strength test and roof strength test). The new Acura RLX body is made of 55% high-strength steel, of which 7% is hot stamped with a yield strength of 1500 MPa; another 7% has a yield strength of 980 MPa and 6% has a yield strength of 780 MPa.

    The new Acura RLX has a wheelbase of 112.2 inches (2849 mm) and a total length of 196.1 inches (4979 mm). Due to the hybrid system, the weight of the new Acura RLX has increased by more than 300 pounds (136 kg) to 4312 pounds (1956 kg), including the hood, door panels, front fenders, and front and rear bumpers.

Improved fuel economy

    The new Acura RLX Sport Hybrid SH-AWD sports hybrid model has a fuel efficiency of up to 28 mpg in the city and 32 mpg on the highway, compared to the conventional Acura RLX non-hybrid model's 20 mpg in the city and 31 mpg on the highway.

    Head-up displays are becoming more and more popular in the automotive industry, and the new Acura RLX Sport Hybrid SH-AWD will also be equipped with a head-up display. This is the first time that a head-up display has been used in an Acura model, and it can display vehicle speed, compass guidance, graphic navigation, adaptive cruise control system settings, lane keeping system and torque vectoring system information.

    The new Acura RLX Sport Hybrid SH-AWD's main market competitors are Infiniti M and Lexus GS, both of which have launched hybrid versions.