Two reasons 2015 Subaru WRX goes back to the 2.0-liter engine

2015 Subaru WRX gets a new 2.0-liter Boxer engine. What are the reasons for Subaru developing the new 2.0-liter DIT?

The all-new 2015 Subaru WRX is about to make its dealer launch and gets a new 2.0-liter direct-injection turbo engine. When the WRX was first introduced to the U.S. market, it came powered by a 2.0-liter turbo engine. Subaru later upgraded the WRX to get a 2.5-liter turbo. Why did Subaru drop the 2.5-liter Boxer in the WRX in favor of a smaller 2.0-liter powerplant in the new-generation model?

Subaru has thrown off the constraints of tradition and developed a new engine for the new 2015 WRX. The iconic WRX has been the focal point for performance enthusiasts since it was first introduced in 1992. Subaru adopted the name "WRX" to stand for "World Rally Cross" as all WRX versions feature rally-inspired technology, including all wheel drive, stiffened suspensions and turbocharged four cylinder engines.

The 2015 WRX gets a new powerplant that is another evolutionary step for the rally-bred performance car that has become a global automotive legend. It gets new technology that addresses two major areas. The new 2.0-liter direct-injection turbo (DIT) was built for driver performance and also environmental performance.

Subaru says environmental performance was sacrificed slightly for better power and torque performance. Fuel efficiency has greatly impacted performance car purchases in recent years. Every year, fuel economy increases and emissions regulations get stricter. Turbo models cannot ignore this overall market trend, despite engine performance being their best selling point.

Subaru developed the DIT engine to deliver good power and torque performance while also answering market needs in terms of environmental performance. Subaru also added a manual transmission option and developed a sportier DIT platform to keep WRX’s true performance attitude.  

How did they do it? 

Changes to the Forester engine that made its way to WRX include stiffer valve springs and friction-reducing roller rocker arms in place of flat tappets. Those are combined with direct injection, high compression (10.6:1), Subaru Dual Active Valve Control System, a twin-scroll turbocharger, and an intercooler. As a result, the turbo boxer unleashes 268 hp at 5,600 rpm, accompanied by a broad torque curve that peaks at 258 lb-ft over a 2,000-5,200 rpm engine-speed range. This is an increase of 3 hp and 14 lb-ft of torque over the previous-generation’s 2.5-liter turbo.

Direct Injection

Direct Injection (DI) is becoming more common as a highly efficient means of delivering fuel. With DI technology, fuel is injected directly into the cylinder, making it possible to cool the interior of the combustion chamber using the latent heat of fuel vaporization. Optimal air mixture for combustion near the plug is promoted using DI technology. Even when the overall air-fuel ratio inside the cylinder is low, combustion can be better controlled. What’s the major benefit? The catalyst heats more quickly during warm-up, reducing the amount of exhaust gas emitted into the air.

The 2015 Subaru WRX gets a new powerplant for two main reasons. The new 2.0-liter direct-injection turbo (DIT) was built for improved driver performance and also for environmental performance. It looks like Subaru was able to accomplish both with the rally-bred performance car’s new engine.