First Drive

FIRST DRIVE: 2014 Acura RLX Sport Hybrid SH-AWD

New Acura hybrid system represents a major advance in powertrain technology

2015 Acura RLX - side 3/4 view

BLUE MOUNTAINS, ON – Acura is expanding its flagship luxury sedan lineup with a much-anticipated addition, the 2014 RLX Sport Hybrid SH-AWD. This beautifully appointed sedan is fitted with a unique three-motor hybrid system that complements a 3.5 litre V-6 gasoline engine.

2015 Acura RLX - taillight.JPGWhat makes this system unique is the way Acura has configured this revolutionary drivetrain – one electric motor works in conjunction with the gasoline internal combustion (IC) engine to drive the front wheels while two electric motors mounted in the rear provide power for the rear wheels. There’s no driveshaft connecting the front and rear systems and the rear units each work independently.

The system results in a SH-AWD (Super Handling All-Wheel Drive) system that’s unlike any other AWD system on the planet.

Unique system enhances handling

The SH-AWD system can generate both positive and negative torque – applying power to one wheel while using the regenerative drag on the other– to improve turning ability that surpasses any competitive system.

2015 Acura RLX - front 3/4 view low.JPGWhen negotiating a curve or turn, the positive torque is applied to the outer wheel while the drag on the inner wheel helps the car rotate through the corner.

The whole operation is seamless and undetectable, except for a power distribution display on both the head-up full-colour image on the windshield and the large screen in the instrument panel – and the solid, secure feeling the driver experiences as the RLX carves through the curve.

This system is complex, without doubt, but it is not intimidating for the user. The RLX progresses through the various drive combinations automatically, with choices decided by assessing the driver’s input and road conditions.

Multiple driving modes

For example, the car launches from a standstill in pure EV mode with the two rear motors driving the rear wheels. Under gentle acceleration, the system switches to front-wheel drive, powered by the IC engine and the forward electric motor.

2015 Acura RLX - rear 3/4 view.JPGCruising at low speeds (up to about 80 km/h), the 1.3 kilowatt lithium battery pack delivers power to the rear motors for a RWD configuration. For higher-speed cruising, the IC engine alone drives the front wheels, taking advantage of its efficiency sweet spot at higher rpm. The fact the V-6 is fitted with a cylinder management system that can shut down three cylinders, when power requirements permit, enhances fuel economy on the highway.

Demands for full power, for such maneuvers as overtaking or merging, cranks up all the power sources and delivers maximum output to all four wheels.

Power regeneration to replenish the battery pack can be delivered from just the front wheels, independently from each rear wheel, or from all those sources combined. This feature helps recharge the battery faster than conventional hybrid systems.

Punchy performance

In addition to superb handling this system packs a performance punch. It's no slouch in a straight line.

2015 Acura RLX - engine bay.JPGFirst, that 3.5L, direct-injected V-6 with i-VTEC has impressive output stats on its own – 310 horsepower and 273 lb-ft of torque. Valve timing has been altered and the catalytic converter has been redesigned to help reduce emissions and enhance its fuel efficiency, which ranks best in its class.

The engine is coupled to a lightweight, seven-speed, dual-clutch transmission that is combined with a slim, compact electric motor. There’s a planetary gear built into the motor that acts as both a torque converter and "first" gear. This very efficiently packaged system produces 35 kilowatts and 109 lb-ft of torque, almost instantaneously.

The two compact, high-output electric motors driving the rear wheels, each functioning independently, produce 27 kw (or about 30 horsepower) and 54 lb-ft apiece. Like the front-mounted electric motor, these units also produce maximum torque on tap instantly.

The combined powertrain package generates 377 horsepower and 341 lb-ft of torque. It is the most powerful car Acura has ever built – and kicking the go pedal proves that point.

On the Road

During an afternoon drive on highways and hilly roads, the RLX hybrid was impressive as 2015 Acura RLX - steering wheel and centre stack.JPGthe powertrain delivered snappy acceleration – and a nasty growl from under the hood.

Engaging the Sport mode boosts the entire experience.

While its performance is on a par with sporty V-8 sedans, fuel consumption is comparable to a four-cylinder – NRCan rates this Acura’s fuel consumption at 8.0 L/100 km in city driving, 7.5 on the highway and 7.7 combined, using the new five-cycle test.

Plenty of amenities

As the luxury brand’s flagship sedan, the RLX interior lives up to expectations and there are no 2015 Acura RLX - front seats passenger side.JPGcompromises with the hybrid iteration. Soft, rich leather abounds – there doesn’t seem to be a hard surface in the cabin.

Amenities such as premium audio and connectivity systems are the focus of the centre stack, while the instrument panel sweeps left and right in beautiful form.

Because there is no driveshaft, the tunnel or structural backbone of the platform is considerably smaller in size than 2015 Acura RLX - trunk.JPGconventional AWD systems. This results in class-leading rear-seat leg room.

Trunk space is less than in the non-hybrid RLX – the battery pack has to go somewhere – but the 328 litres of cargo capacity is still very usable.

The trunk opening is generous – 1,187 millimetres wide – and the cargo area will accept four golf bags. There’s also a smaller storage space under the trunk’s floor.

One nit to pick

The only nit I have to pick is with the braking system. As with many regenerative braking systems, the brake pedal is difficult to modulate.

2015 Acura RLX - wheel.JPGAcura engineers have attempted to address this issue by incorporating an electric servo system that first engages an electrical braking action, then engages a hydraulic system as demand increases. It’s supposed to provide a more linear, stable feel, but I couldn’t get comfortable with it during the afternoon drive.

This issue aside, the system does stop the car with authority. Because the RLX hybrid is about 110 kilograms heavier than its sibling, larger brake rotors have been used to overcome the added weight.

The RLX Sport Hybrid is offered only one way – fully loaded. The SH-AWD Elite sedan has a list price of $69,990, which compares favourably with Infiniti’s Q70h and Lexus's GS450h, similarly equipped.

However, the pricing shouldn’t be the prime reason for checking out the RLX Sport Hybrid – to truly appreciate its capabilities, you really need to drive it. I’m betting you’ll be impressed.

2015 Acura RLX - front view.JPG2015 Acura RLX - headlamp detail.JPG2015 Acura RLX - rear seat.JPG

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