The Acura RLX finds itself in a performance arena that used to have the gentle ambiance of the Westminster Dog Show, but now feels more like Thunderdome. When the former RL was new, 300 horsepower was supercar territory; now, that's the base output for some of the RLX's hottest competition, and the 400-hp mark is an easy hurdle for some of its pricey mid-size luxury competitors.
Even among the milder editions of those other aspiring sedans, the Acura RLX's 310-horsepower, 3.5-liter V-6 isn't a spec-page leader, nor is its 272 pound-feet of torque. It's up 10 hp and 1 lb-ft over the RL's 3.7-liter V-6, but it pales next to the Lincoln MKS EcoBoost's 365 horsepower, or the Hyundai Genesis R-Spec's 429 hp.
It's an aural component that puts some waveform into the engine's straightforward delivery. There's not much urgency in the way it pulls uniformly away from a stop, or in its relaxed uptake. It's a contrast to the Lexus GS, which has some peaks whipped into its performance, though it doesn't necessarily feel any quicker than the Acura RLX--both sit squarely in the 6-second 0-60 mph range.
The RLX's automatic transmission nets shift paddles and a sport shift mode this year, but no more gears. It's a six-speed automatic with very smooth upshifts, less invisible downshifts. The top-rated sedans in the segment are changing over to eight-speed automatics, as is the Chrysler 300. The ZF eight-speed that's nearly universal sets a high bar, and the RLX could use more tightly spaced gears to accelerate more quickly off the line.
As for the gas mileage benefits of more gears, the RLX doesn't need much help. It's estimated at 20/31 mpg, or 24 mpg combined, near the Chrysler's numbers with two fewer gears.
Step up a notch, and you get to the RLX Sport Hybrid SH-AWD model, which packs a special new three-motor hybrid system that previews technology to be used in the future NSX supercar. With a 3.5-liter V-6 and a new seven-speed dual-clutch automated manual gearbox that has a 35-kW motor built in, what's under the hood already has the makings of a strong, smooth hybrid system. But what makes it a fun, all-weather machine is that there's also a new Twin Motor Unit mounted to the rear subframe, including two 27-kW motors that can act together, on their own, or in a regenerative mode to add available traction or to affect the car's composure in corners.
In all, the SH-AWD hybrid system makes 377 horsepower and 377 pound-feet of torque.
How does the RLX handle? It really depends which model you go with. Along with the XTS, MKS, and Volvo S80, the front-drive model is in a niche divided from the traditional luxury marques by heritage as much as orientation. At BMW, Mercedes, and Jaguar, rear-wheel drive is the norm, and all-wheel drive is an option for marketing's sake. Audi is the grey area.
Acura's on the other side of the fence. The RLX and the RL before it have always been front-drivers, and the dynamic difference between Acura and those brands has only shrunk a little bit. The RLX has a conventional suspension tuned for comfort first, with a bit of lively feel dialed in via electric power steering and a trick pair of actuators at the rear wheels. The RLX's steering has a light touch on center that's very noticeable at parking speeds, entirely intentional, before it transitions to a more consistent heft. The transition's less obvious at speed, where the ability to steer its rear tires becomes the RLX's most significant new hardware bullet point.
The RLX's rear steering--Precision All-Wheel Steer, or P-AWS--is technologically extravagant, for what the RLX wants to be. P-AWS puts an actuator on each rear wheel and keeps tabs on vehicle speeds and steering motions, so it can feed in minute amounts of rear-steer to give the RLX more stable road feel. In lane changes, all four wheels move in the same direction. On a curving road, P-AWS can steer the rear wheels up to two degrees in the opposite direction of the front wheels, to cut a sharper line. It's an effect that can be helpful in daily driving, mitigating some of the width that's been baked into the RLX's platform (maybe for interior room, maybe also to accommodate some of the hardware on the way in the RLX hybrid and NSX).
Under extreme conditions, like on the stretch of Sonoma Raceway where Acura let us press the system, P-AWS can make you rethink the way you approach corners and react to them, by virtue of the way it transitions through its rear-steer spectrum. Drive it quickly in an uphill straight line, then dive down and deeply left, and the quick oversteer set up by P-AWS is unlike any other system before it. It's a glint of edge in a car that doesn't necessarily need for one, or pretend to one.
The powertrain and steering work in concert with a conventional suspension design to give the RLX a comfortable, composed ride. It's sprung and damped well enough to absorb stretches of broken pavement with little fuss, and it leans into corners casually and undramatically. For that kind of driving duty, you'll never miss an adjustable suspension system or adaptive shocks like the ones commonly found on competitors, but absent here. Those systems can be tailored to a wider range of performance limits, and the RLX doesn't intend to ultra-high performance. There's no M or AMG edition in the works. It's a mono-spec machine that knows its limits, and makes the best of them.
Go with the Sport Hybrid SH-AWD model and you should ignore the last several paragraphs entirely. This is the model to have, if you like the idea of an under-the-radar sport sedan with surprisingly good dynamics. Head into a corner a little too hot, and using what feels like physics-defying magic at the rear wheels, the RLX sends power selectively to each of the rear wheels—the outside rear wheel especially—nudging your trajectory back right where it should be. It's rather unsettling at first, because you feel that nudge from the driver's seat, but not through the steering wheel.
But the novelty doesn't wear off. We can see the RLX's attributes being just as useful on a weather-slicked highway, making an emergency maneuver, as we can on the mostly empty backroads where we test-drove the RLX.
Otherwise with the Sport Hybrid, it's extremely responsive to stabs of the accelerator, and it accelerates almost like an electric car--with the motor systems filling in neatly wherever you can hear the dual-clutch gearbox grab for the next gear. It's an entirely different, more exotic (and exciting) driving experience than in the front-drive RLX--and a bit out of sorts, given the conservative presentation.