Subaru’s Boxer Turbo Fine Fit for WRX

As part of last year’s Ward’s 10 Best Engines competition, we tested Subaru’s 2.0L “FA” turbocharged boxer when it was new in the Forester, so why are we evaluating it again?

Because it now makes an extra 18 hp in the sporty '15 WRX and features lots of fresh content intended to extend the performance envelope, including new camshafts, valves, rocker arms, cam sprockets, alternator, ignition coil and electronic controller. Plus, valve springs have been re-engineered to accommodate higher revving.

In addition, the WRX engine now redlines at 6,700 rpm (with 6-speed manual transmission), instead of 6,000 rpm in the Forester. And the torque peak lasts longer in the WRX – from 2,000 to 5,200 rpm, instead of 4,800 rpm in the Forester. The changes allow the WRX to develop its peak power using 15.9 psi (1.09 bar) turbo boost, rather than 17.1 psi (1.17 bar) in the Forester.

The boxer in the Forester wasn’t bad last year, but in general the class of 2.0L turbocharged 4-cyl. gasoline engines left us a bit disappointed, if you recall. Not a single one made the list, even though we tested seven of them.

This year, once again, we have seven new or improved gasoline 2.0L turbo-4s among the 38 nominees to evaluate, and a number of them, including the WRX boxer, are drawing solid reviews from the judges.

Stacking up the WRX to last year’s Forester, the little rally car is 355 lbs. (161 kg) lighter and $6,500 less expensive. It sounds much more emotive, thanks to a new exhaust system that eliminates one chamber in the muffler and shortens the internal tubing. The giant scoop on the hood pulls in more air to help the intercooler do its job.

But the key elements from last year’s Forester application carry over to the WRX, including bore and stroke dimensions, compression ratio, direct injection, twin-scroll turbocharger and Dual Active variable valve timing on both intake and exhaust valves.

Lots of Power, Plus 27 MPG

On the fuel-economy front, most editors driving the WRX managed to top 27 mpg (8.7 L/100 km), which is pretty good considering how much this engine enjoys spinning above 5,000 rpm.

When we tested the Forester last year, the staff averaged about 24 mpg (9.8 L/100 km). Oddly enough, both vehicles carry the same EPA highway rating of 28 mpg (8.4 L/100 km), but the Forester’s 23 mpg (10.2 L/100 km) city rating is 2 mpg (0.8 km/L) better than that of the WRX.

We’ve spent a lot of time comparing the WRX to last year’s Forester, but perhaps more important is how it stacks up with the smaller turbos, such as the Alfa Romeo 4C’s riotous 1.7L, the VW Golf’s excellent 1.8L (a returning winner) and the 1.6L engines in the Hyundai Sonata Eco and Ford Fusion. The WRX beats them all in power, but smaller engines have the upper hand in fuel economy.

And how about some of these 2.0L turbo I-4s? The WRX faces direct challenges in this displacement from the Hyundai Sonata, Lexus NX, Mini Cooper S and Volvo S60. One version of the S60, with the T6 2.0L, employs both turbocharging and supercharging. And don’t forget the VW GTI and Audi S3, which use amped-up versions of the EA888 2.0L turbo-4.

Finally, the WRX powertrain probably should be compared with the new 2.3L EcoBoost 4-cyl. in the Ford Mustang and Lincoln MKC. Yes, the Mustang pummels it in output, at least on paper, but the WRX should prevail in the fuel-economy comparison.

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'15 SUBARU WRX 2.0L "FA" BOXER TURBO Specifications