Fuji Heavy Industries Ltd.: 2.5L Turbocharged DOHC H-4 Boxer

Subaru’s excellent 2.5L turbocharged boxer engine provides the ideal mix of restrained power and frugal sensibility. It’s the cure for the boring family sedan.

Tom Murphy, Managing Editor

December 21, 2009

3 Min Read
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Special Report

Ward’s 10 Best Engines

The last time the Subaru brand won a 10 Best Engines award, in 2004, the list was fueled by testosterone.

The rally-ready 300-hp 4-cyl. WRX STI was in good company with similar high-octane entries such as the Audi S4, BMW M3 and two Dodge Ram pickups, one with a Hemi V-8, the other with a 5.9L heavy-duty diesel strong enough to pull a freight train. The average displacement on the list was 3.5L.

Six years later, there is only one V-8 on the list, no pickups, an average displacement of 2.7L and a subdued tone reflecting a shifting market that values fuel efficiency.

The all-new Subaru Legacy GT’s 2.5L turbocharged 4-cyl. boxer engine makes this year’s 10 Best Engines list because it provides the ideal combination of restrained power and frugal sensibility.

With its horizontally opposed four cylinders churning out 265 hp and a 258 lb.-ft. (350 Nm) torque peak readily available at 2,000 rpm, the intercooled 2.5L gives the Legacy GT all the punch it needs to compete in the near-luxury midsize car segment.

This engine – in a less edgy state of tune – shares its architecture and many of its specs with the turbocharged 2.5L boxer that took our breath away in the WRX STI six years ago. But judges were equally impressed this year.

“Beautiful power delivery, even when accelerating in high gears,” writes Ward’s Dealer Business Editor Steve Finlay on his score sheet. “It’s fast, yet exquisite.”

By today’s standards, the 2004 STI’s 2.5L could be perceived as twitchy, raucous and tiresome. Today’s market calls for something more practical – yet still fun and technically advanced – and Subaru delivers it in the Legacy GT.

The new iteration has the turbocharger mounted beneath the engine, rather than on top, which is where most turbos reside. The new placement puts the turbo close to the exhaust stream, which reduces emissions and turbo lag at low engine speeds.

Subaru has used this approach on a 2.0L diesel engine in Europe, but this is the first gasoline application, as well as the first application in the U.S. A side benefit: It lowers the car’s center of gravity, improving handling.

The new Legacy’s strut front suspension attaches to a redesigned engine cradle using a “wide-spread” mount system. That improves noise, vibration and harshness and quells the boxer’s unique rasp.

The Environmental Protection Agency rates the Legacy GT’s fuel economy at 18/25 mpg (13-9.4 L/100 km) in city/highway driving, but some judges managed better than 28 mpg (8.4 L/100 km).

When power is required while cruising, the turbocharger enables a delicious torque swell that builds to a crescendo from 3,200-5,200 rpm, paying homage to its sporty legacy in the STI.

“I see myself cruising with the wife and daughter in her car seat, and then letting it rip when I’m by myself,” Associate Editor James Amend writes of the Legacy GT.

Consider Subaru’s excellent 2.5L turbo the cure for the boring family sedan.

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Ward's 10 Best Engines is a copyright of Penton Media Inc. Commercial references to the program and/or awards are prohibited without prior permission of Ward's Automotive Group.

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2010 10 Best Engines

About the Author(s)

Tom Murphy

Managing Editor, Informa/WardsAuto

Tom Murphy test drives cars throughout the year and focuses on powertrain and interior technology. He leads selection of the Wards 10 Best Engines, Wards 10 Best Interiors and Wards 10 Best UX competitions. Tom grills year-round, never leaves home without a guitar pick and aspires to own a Jaguar E-Type someday.

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