Sports Hybrid Car
Better Reaction Times All Around
The nonhybrid MDX SH-AWD is a tough act to follow; it’s among the best-handling three-row crossovers, with quick, well-weighted steering and well-controlled body motions. Both MDX models feature an all-wheel-drive system—optional in the regular one, standard in the hybrid—that sends more torque to the outside rear wheel during hard cornering, but the Sport Hybrid goes a step further with the ability to apply resistance (and recover energy) at one rear wheel while it’s delivering forward momentum to the other. It thus achieves a sophisticated and more nuanced form of torque vectoring. The hybrid system also does away with a mechanical connection between the engine and the rear axle. Instead, a Twin Motor Unit (TMU) packages two 36-hp motors together at the rear. They fill gaps in the engine’s torque curve to sharpen accelerator response in the hybrid compared with the conventional model, and Acura engineers boast that the system takes just 90 milliseconds to fully adjust the torque distribution among the wheels versus about 0.2 second in the regular MDX. In front, a third, 47-hp electric motor spins with the input shaft of the seven-speed dual-clutch automatic transmission and has three roles: delivering supplemental torque, helping smooth out shifts, and acting as a generator.
As for the transmission, it’s a partner in this system’s quick reaction times. By losing the ZF nine-speed automatic, which can bumble over its bounty of ratio choices (and sometimes fumbles the shifts themselves with a shudder), the seven-speed and hybrid motor system are all business, ripping through the gears with quickness and grace. You hear them work more than feel them, and, because of the hybrid system, the rush of passing power starts even before the transmission has downshifted.
The gasoline engine steps aside as the headliner of the show, even though it remains the essential piece. In place of the direct-injected 3.5-liter V-6 in other MDX models, the hybrid has a 3.0-liter V-6 with port injection, the smaller displacement enabling it to skirt a China-market tax on larger engines. The entire system makes 321 horsepower and 289 lb-ft, or 31 hp and 22 lb-ft more than the nonhybrid models.
The hybrid system brings the V-6 seamlessly into the mix with a wet multiplate clutch, finessing the low-speed drivability issues that can plague such a setup. Accelerate gently and the MDX hybrid launches silently, as a rear-wheel-drive electric vehicle. The V-6 comes on shortly thereafter, although it often switches off when coasting (at speeds up to 56 mph). We also saw it cycle off in steady 40-mph cruising. /p p The fine MDX driving experience hasn’t been adulterated in any other way. It includes well-blended brakes and precise, nicely weighted steering. There’s a fair amount of body lean, as expected in an SUV like this, but the adaptive dampers do a great job filtering out road harshness. Push hard into tight corners and you might find yourself dialing in too much steering input, as the outside rear motor nudges the vehicle’s rotation, preempting understeer. A quick loop in a Lexus RX450h—the top seller among the MDX hybrid’s U.S.-market rivals—showed a sharp contrast with the way Acura’s hybrid system doesn’t change accelerator response as the power sources swap in and out, thus reinforcing the idea that the system works as one cohesive unit. /p a name="eztoc8834186_0_2"/h3strongAiming to Blend In/strong/h3 p Compared with the NSX or even the RLX, there was a greater effort to make the hybrid technologies invisible in the MDX, according to product planning manager Gary Robinson. The priorities here were simply strong acceleration and balanced performance, and outside of knowing when the engine switches off and on, it’s hard to discern what the hybrid system is doing and where torque is being delivered. /p table border="0" cellpadding="2" cellspacing="0"x">
There nevertheless are four driving modes in the Sport Hybrid, up from three in other versions of the MDX. They vary throttle response, steering effort, and damper behavior. The one that’s hybrid-exclusive and takes advantage of this model’s added performance is Sport+, which keeps the engine running all the time, freeing up the front motor to maximize acceleration and to assist with shift quickness.
Acura says the hybrid kit adds 227 pounds to the curb weight of the MDX versus the standard AWD model—which is already roughly 200 pounds heavier than an equivalent front-drive version. But because much of the hybrid hardware is mounted low in the chassis, the Sport Hybrid has a center of mass that’s about an inch lower. The fitment of all this extra hardware has no effect on packaging. Ground clearance is the same as that of the standard MDX. Seating is still comfortable for five in the first two rows (or four, if you get the Advance model and its second-row captain’s chairs) and good enough for kids in the third row; the seats fold neat and flat; and cargo space is uncompromised.
If the motor systems around the axles are the muscle of the hybrid system, the Intelligent Power Unit (IPU) and Power Control Unit (PCU) are its brain and nerve center. Both have benefited from NSX development, and they’re mounted on additional structures (with crossmembers to help protect them) that span the width of the MDX’s underbody—essentially where the driveshaft otherwise would go.
The PCU is liquid cooled, while the IPU, where the 72-cell, 1.3-kWh lithium-ion battery pack lives, is located under the center console and cooled with air from the cabin.
Other than badging, there’s not much to visibly distinguish the hybrid from other versions. All MDXs received a light refresh for 2017, one that’s most noteworthy in front, where Acura shed the last remnants of the former model’s awkward metallic beak, subbing in a more conventionally styled grille. The hood gets some corresponding new character lines, there are new wheels, and the return of dual exhausts sum the exterior changes for the 2017 MDX lineup. Inside Acura has introduced second-row captain’s chairs and revamped some of the trim and surfaces. The company expects the MDX hybrid’s target buyer to be both significantly younger and more affluent than those who go for the nonhybrid models. Considering that, the hybrid’s interior feels conservative—if a bit drab—for the mission. And years after its introduction, Acura’s dual-screen infotainment system still confounds and infuriates.
Acura expects to sell only 5 percent of all MDXs in hybrid form, but perhaps that will prove to be an underestimate. For all the complexity, the hybrid gear makes the MDX better to drive and less thirsty. Here, the halo seems real.
