System aids awd, cornering, along with power

Acura gets more out of RLX hybrid motors

System aids awd, cornering, along with power

The sport hybrid system allows the RLX to combine takaburi, which translates to "smart exhilarating luxury," with inomama, which means "handling at the will of the driver," said Hitoshi Aoki, the vehicle's chief engineer.
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SAN FRANCISCO -- Acura has taken its RLX sedan, strapped to a three-motor hybrid system that gooses horsepower to 377 from 310 with the added benefit of all-wheel drive, and transformed its vanilla full-sized luxury sedan into a stronger competitor.

The basics: Under the hood of the RLX Sport Hybrid is the same 3.5-liter direct-injection V-6 as the base RLX, but it gets a seven-speed, dual-clutch transmission mated to an electric motor. When combined with the two hybrid motors linked to the rear wheels, it creates "the most powerful Acura ever built."

The electric motors in Acura's hybrid system are designed to do more than boost power and save fuel. During cornering, the motors also power a torque-vectoring system that sends positive torque to the outside rear wheel and braking torque to the inside rear wheel. In theory, this creates an "optimal yaw moment," or more precise turn-in.

The hybrid motors allow the car to cruise in "EV mode" at up to 50 mph, with the gasoline engine off and transmission uncoupled. At cruising speed when the engine is running, cylinder deactivation maximizes fuel economy.

Many hybrids kill the engine when the car is at a full stop, but the engine's restart can often be abrupt and jarring. The RLX has active engine mounts and a changed camshaft profile to reduce that shock. Under braking, the rear motors provide regenerative power to the lithium ion battery.

The hybrid system is similar to what will be installed on the NSX supercar that comes in 2015.

Acura's new flagship
The RLX Sport Hybrid's all-wheel-drive system uses a pair of electric motors to drive the rear wheels.
 2014 Acura RLX Sport Hybrid2013 Lexus GS 450h
Wheelbase112.2 in.112.2 in.
Length196.1 in.190.7 in.
Width74.4 in.72.4 in.
Height57.7 in.57.9 in.
Curb weight4,312 lbs.4,190 lbs.
Base engine3.5-liter V-63.5-liter V-6
Total system horsepower377 hp338 hp
EPA mpg28 city/32 hwy.29 city/34 hwy.
Base price*N/A$60,510
   
* Includes shipping

Standard equipment in the RLX Sport Hybrid includes two information screen displays and a 14-speaker stereo.

Notable features: Because it's a front-wheel-drive car, the RLX has acres of legroom compared with its rear-wheel-drive competition. Acura claims its LED headlights have longer, wider and more defined "throw" of light than the high-intensity discharge lamps of the competition.

The hood, door panels, fenders and bumper beams are made from aluminum instead of steel, saving 76 pounds. The traditional gearshift has been replaced by four buttons, with reverse gear requiring a finger-pull upward to activate.

Standard features include a power moonroof, paddle shifters, retracting mirrors, rain-sensing wipers, keyless entry, two information screen displays, navigation with live traffic, 12-way power front seats, 14-speaker stereo with satellite radio and Pandora Internet radio, 19-inch aluminum wheels with in-wheel resonators that reduce noise by 7 decibels and a head-up display that shows speed, turn-by-turn navigation and other status reports.

Safety features include: seven airbags, hill-hold brakes, blind-spot warning and wide-view backup camera. Optional safety features available as a package include lane departure warning, adaptive cruise control with "low speed follow" and a collision warning system with automatic brake activation.

What Acura says: The sport hybrid system allows the RLX to combine takaburi, which translates to "smart exhilarating luxury," with inomama, which means "handling at the will of the driver," said Hitoshi Aoki, the vehicle's chief engineer.

Compromises and shortcomings: The awd system is fwd at heart, and with a 57/43 weight distribution, the front-heavy car's corner-entry handling still tends to understeer -- despite a front double-wishbone suspension. The RLX's on-center feel is vague, even in sport mode, with at least 15 degrees of steering wheel play before any real reaction occurs. The brakes are oddly numb at high velocities, yet choppy at parking lot speeds. Even though the RLX is the automaker's only platform not shared with a Honda-badged product, the interior cannot escape its Honda roots and lacks the panache of the Lexus GS' stylish bamboo-trimmed interior.

The market: Acura will announce pricing closer to its spring 2014 launch, but expect the RLX Sport Hybrid to compete closely with the Lexus GS 450h, Mercedes-Benz E400h and BMW ActiveHybrid5. The typical customer is a 48-year-old man in a household that earns more than $200,000.

The skinny: The idea is V-8 performance with four-banger fuel economy, and the reassurance of well-planted all-wheel drive.

It doesn't quite accomplish any of the above but comes close. At a price point likely around $60,000, that may not be good enough to win customers of prestigious luxury brands over to Acura's "smart luxury."

You can reach Mark Rechtin at mrechtin@crain.com. -- Follow Mark on Twitter


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