New sporty Subaru WRX passes IIHS test

  • 10-Dec-2013 05:43 EST
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The Subaru WRX's new direct-injection turbo/intercooled engine is rated at 268 hp (200 kW) and 258 lb·ft (350 N·m).

The WRX is one of Subaru’s iconic compact sports sedans, and the 2015 model the company featured at the Los Angeles Auto Show didn’t skip any key performance points. It has a new smaller displacement but more powerful Boxer engine and a choice of manual and automatic drivetrains, each with a specific all-wheel-drive system.

Considerable engineering attention was devoted to making sure the car passed what is becoming a requirement for acceptance on new cars: the IIHS (Insurance Institute for Highway Safety) front offset barrier overlap test. Subaru relies on its ring-shaped body-structure approach in which the A-pillars, roof, and underbody structure form a rigid ring. This not only helps with roof safety requirements, but provides a basic level of strength to which additional front structure contributes to distribute concentrated crash energy in the offset barrier test.

Structural changes in front

The redesign starts at the front, with a strengthened bumper beam and reinforced mounts. The A-pillar is an ultra-high-strength hot-stamped design, and a triangular reinforcement was added where the front rail meets the A-pillar joint. Additional fasteners were installed for the attachment of the front doors to the A-pillar to help maintain door location, which also contributes to management of crash energy in the IIHS test.

The IIHS test result is impressive in light of the fact that the windshield rake was increased, the A-pillar is thinner, and the base of the A-pillar was moved some 8.0 in (203 mm) forward. This series of steps was taken (along with lowering the dashboard) to improve visibility at the forward sides, where the presence of outside mirrors typically creates blind spots in many cars.

The interior package is roomier thanks to a 1.0-in (25-mm) increase in wheelbase to 104.3 in (2648 mm). Overall length of the sedan, at 180.9 in (4595 mm), is 0.6 in (15 mm) greater than the previous edition. There is no current plan for a new edition of the hatchback, a Subaru spokesman told AEI.

New powertrain

The manual drivetrain is Subaru’s new six-speed manual, which replaces a five-speed. (The WRX STI, the top performance model in the line, has had a six-speed, but that is an Aisin-supplied unit, whereas the WRX gearbox is Subaru’s own design based on the one in the Forester.) The WRX manual has a viscous coupling AWD unit with an initial 50-50 front-rear torque distribution.

The AWD unit for the WRX's optional Lineartronic CVT (continuously variable transmission) is a center differential type with a planetary gearset and an electronically controlled clutch adapted from previous applications in the Legacy, Outback, and Tribeca. Its initial front-rear setting is 45-55. The CVT itself offers a choice of two simulated shift modes: six ratios or, in Sport Sharp mode, eight ratios. They also can be selected manually with the paddle shifters. The CVT is the first automatic in the WRX since 2008. 

The CVT AWD system is integrated with the electronic stability control system, with software strategy that uses the anti-lock brakes to add the capability for torque vectoring to improve handling in turns.

The Boxer engine, a 2.0-L four-cylinder with double-scroll turbocharging with intercooling, is a perfect "square" at 86 and 86 mm (3.39 x 3.39 in) bore and stroke. It replaces the 2.5-L intercooled turbo previously used. The new engine has direct fuel injection, variable intake and exhaust valve timing, and a 10.6:1 compression ratio (vs. 8.4:1 for the previous 2.5-L). This new engine is rated at 268 hp (200 kW) and 258 lb·ft (350 N·m), a moderate increase (primarily in torque) from the 265 hp (198 kW) and 244 lb·ft (331 N·m) of the 2014 model's 2.5-L. Additionally, the 2015 torque curve is flat, the peak reached at 2000 rpm and maintained to 5200 rpm.

Improved fuel economy

Those performance numbers call for premium gasoline (as did the 2.5-L in the 2014 model), and when you factor in the AWD, the EPA-rated fuel economy is a modest-but-acceptable 21 mpg city/28 mpg highway EPA with the six-speed, 19 mpg city/25 mpg highway for the CVT. This still represents a measurable improvement vs. the 2014 WRX, which had only the five-speed manual and an EPA rating of 19/25.

Although the WRX, which is built on the Impreza platform, is a performance sedan, as noted there’s the STI step-up to come. The 2014 STI has a 2.5-L Boxer rated at 305 hp (228 kW) 290 lb·ft (393 N·m) and a more sophisticated center differential AWD system with a helical limited-slip differential in front and a Torsen limited-slip in the rear.

The WRX continues its “stealthily” conservative appearance to go with its pocket rocket image, but the Legacy line is in a separate marketing area. The next generation concept of Subaru’s family sedan also was on display at the show, and it’s clearly staked out a stylish look. However, what Subaru exhibited is still called a concept, and Subaru has a history of toning down concepts for production.

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