By Drew Johnson
Thursday, Dec 19th, 2013 @ 11:45 am
 

If some is good, more must be better.

Nearly a year after introducing its two-wheel drive, 310 horsepower RLX P-AWS (Precision All-Wheel Steering) , Acura is now rolling out its RLX Sport Hybrid, which boasts all-wheel drive and 377 horsepower.

But there is more to this equation than the raw numbers would suggest. The RLX Sport Hybrid isn't just some variant of a current Honda hybrid; No, this vehicle is equipped with a totally bespoke gas-electric drivetrain that includes three electric motors and high-tech goodies like electric torque vectoring. In fact, the RLX's drivetrain is so advanced that a variation of it will be used in the upcoming NSX supercar.

That certainly sounds impressive, but does all of that 'more' actually add up to a better flagship sedan? Come with us as we find out.

Kissing cousins

As the RLX Sport Hybrid SH-AWD (short for Acura's Super Handling All-Wheel Drive) is based on the front-wheel drive RLX, it should come as no surprise that the two models are styled almost exactly the same. However, there are a few cues to help the hybrid stand out as the range-topping model.

Up front, the Sport Hybrid features a dark chrome version of Acura's signature shield front grille, which, to our eyes, looks more attractive than the chrome design used on the base model car. The RLX Sport Hybrid also gets LED fog lights in place of conventional units.

Unique 19-inch wheels are the only other styling diversion from the regular RLX, aside from a few badges.

The RLX remains a handsome, albeit somewhat conservative, design in Sport Hybrid guise, but we're still not sold on Acura's jewel-eye headlights.

Changes inside are limited to a gray upper dash section and a new push-button shifter. The console-mounted shifter could benefit from more robust-feeling buttons, but the new design is at least straightforward to use.

As with the front-wheel drive RLX, we found the materials used in the RLX Sport Hybrid to be top notch, even in areas you wouldn't expect, like around the footwells and under the dash. The RLX's front thrones remain some of the most comfortable in the biz and rear seat occupants will benefit from the most legroom in the segment.

High-tech powertrain

Peel away that familiar styling, though, and you'll find an all-new drivetrain. The only carryover from the front-wheel drive RLX is a 3.5L V6, but even it has been massaged to make the most of the gas-electric setup.

Output from the 3.5-liter V6 is unchanged at 310 horsepower (torque is up 1 lb-ft to 273), but Honda has updated the V6's camshaft valve time to reduce engine vibrations. There is also a faster-acting catalytic converter aboard to better handle the vehicle's stop-start function.

The RLX Sport Hybrid's gas engine is mated to a compact electric motor - adding another 47 horsepower and 109 lb-ft of torque -- via a new seven-speed, dual-clutch transmission. Unlike Honda's previous integrated motor designs, the gas engine can be totally decoupled from the electric drivetrain, resulting in improved efficiency.

In place of the RLX P-AWS' rear-wheel steering, the RLX Sport Hybrid features a pair of electric motors combining for 72 horsepower and 108 lb-ft of torque. The rear motors can operate in unison or independently, allowing for torque vectoring. The system can also drag on a specific rear wheel, which further aids in cornering.

The entire system is backed by a lithium-ion battery pack located beneath the car's center console.

A quick calculation shows that our power figures don't add up, but that's not a mistake - the gas engine and electric motors reach their peak power levels at different speeds, meaning full power from all three sources is never available at one time.

Behind the wheel

Fire up the RLX Sport Hybrid and you'll notice, well, nothing. The RLX hybrid defaults to Rear Drive Mode, which means noise-free motoring thanks to the car's rear-mounted electric motors. The RLX can operate in Rear Drive Mode at speeds up to 50 mph.

The rear motors give the RLX an extra boost of acceleration off the line, but we don't think that's their biggest benefit. Most vehicles equipped with dual-clutch transmissions suffer from lurching at slow speeds, but the RLX's electric motors eliminate that mechanical flaw. All dual-clutch vehicles should be made this way.

Once underway, the RLX can be powered by its gas engine, electric motors, or any combination of the two. When the car is coasting or cruising downhill, all four wheels can provide battery regeneration.

Acura estimates that its hybrid technology will net the RLX EPA ratings of 28/32/30 mpg city/highway/combined.

But, as its Sport designation suggests, the RLX hybrid is about more than just saving gas.

Press the "Sport" button on the center console and the RLX Sport Hybrid does its best impression of a V8-powered sedan. The Sport mode disables the RLX's auto stop-start system, resulting in quicker throttle response and constant power generation so the electric motors never run out of juice. The Sport mode also holds gears longer and performs down shift blips.

With the Sport mode engaged we were able to record a 0-60 time of 5.3 seconds, which was right around half-a-second faster than the regular driving mode. The electric motors can provide an extra boost up until about 75 mph, but from there on it's up to the gas engine to keep the RLX accelerating.

More than just straight-line booster rockets, those electric motors also help the RLX in the twisties.

The RLX's rear motors constantly apply positive and negative torque to each rear wheel, which convincingly replicates the feeling of a rear-wheel drive vehicle. The RLX Sport Hybrid can also "drag" its front brakes (which are slightly larger than the discs on the standard car) to help it get around a tight bend.

Torque steer is virtually non-existent in the RLX Sport Hybrid and we only encountered front-end "push" - a typical trait of front-wheel drive vehicles - when cornering at the limit.

Steering feel isn't the RLX Sport Hybrid's strong suit, but it's certainly better than some of the other steering systems offered in this segment. Overall we found the RLX's steering system to be direct and accurate, although not totally without fault. During some tight maneuvers we found that a slight steering input could result in a bigger direction change than intended. That sensation was likely due to the outer rear-wheel motor jumping to action and providing a sudden boost of turning force. It should be noted that our test vehicle was a pre-production model, so we'll hold judgment until the final version of the RLX hybrid joins our test fleet.

The details

The RLX Sport Hybrid shares many of its safety and technology features with the RLX P-AWS but, as you would expect, more of those goodies are standard on the more expensive flagship. All RLX Sport Hybrids ship from the factory with Acura's technology Package, which includes Lane Departure Warning, Navigation, Blinds Spot Monitoring and Forward Collision warning. The Tech pack also features a Head-Up Display, which is not available on the standard RLX.

Those wanting all the bells and whistles can order the Advance Package, which adds Active Cruise control with Low Speed Follow, Collision Mitigation, Lane Keeping Assists, heated rear seats and a Krell Audio system.

Pricing for the 2014 RLX Sport Hybrid will be announced closer to the car's spring 2014 launch, but look for the Technology Package trim to list from about $60,000, with the Advanced package bumping the needle to $65,000.

Leftlane's bottom line

After being somewhat let down by the RLX P-AWS, we're happy to report that the RLX Sport Hybrid is much more befitting of Acura's flagship tag. Though most of the amenities from the RLX P-AWS' carryover, the hybrid system - which manages to improve both efficiency and overall performance - transforms the RLX Sport Hybrid SH-AWD into something that feels more special.

We're not sure if the market is quite ready for a $65,000 Acura sedan, but the RLX Sport Hybrid is definitely worth a look if you're considering more expensive option like the Lexus GS 450h or the BMW Active Hybrid5.

2014 Acura RLX Sport Hybrid base price, $60,000 est.

Photos by Drew Johnson.