Subaru Boxer Engine Explained

THE SUBARU BOXER ENGINE

At the heart of EVERY Subaru is the Subaru Boxer Engine; named for the horizontal movement of the pistons - much like boxers throwing punches. On this page you will learn why Subaru chose the Boxer engine, how it works, and the safety, performance and handling advantages it brings to the driving experience.

BENEFITS OF THE SUBARU BOXER ENGINE

· Flat layout allows engine output to flow directly into the transmission. This linear flow of power reduces engine components and inefficiencies, resulting in better fuel economy. Subarus are the most fuel efficient AWD vehicles in America, often getting better gas mileage than its FWD competitors.

· By lowering the center of gravity of the engine, you also lower the center of gravity of the entire vehicle. A lower center of gravity = more responsive - particularly when cornering or doing evasive maneuvers.

· Less vibration. The natural counter punch of the opposite piston cancels out unwanted vibration where inline and v-type engines require additional components to accomplish this.

· Safety. In the event of a frontal accident, the boxer engine's low center of gravity allows the engine to drop "below" the passenger compartment instead of in it.

As you can see, the Subaru Boxer Engine is itself a study in symmetry and delivers an impressive amount of power from such a small footprint. Combined with Subaru's Symmetrical All-Wheel Drive, both of these aspects combine to deliver a safer, more stable platform that is perfectly aligned along the center-line of the vehicle resulting in better balance. BETTER BALANCE = BETTER CONTROL.

SUMMARY

For over 45 years Subaru has been solely committed to the Subaru Boxer Engine in ALL of their models. The innovative design is part of Subaru's core DNA. Why don't other manufacturers use it? Porsche does in a few of their models including the Boxster, Cayman and 911 models. Porsche states, "This flat, short design results in a very low center of gravity and extremely smooth running."

For Honda, Toyota and others, it would be nearly impossible to benefit from a boxer engine because their architecture is not designed for the transmission to sit behind the engine. With inline engines the transmission often sits to one side of the engine, thus creating imbalance.

While you may not be doing evasive maneuvers on a test drive, isn't it nice to know that as an owner you have that capability if you need it. That's the Subaru Boxer Engine!

SUBARU BOXER ENGINE
PERFORMANCE BY MODEL

It seems as though Subaru offers the perfect size boxer engine for each vehicle type including:

2.0 liter 4 cyl DOHC engine w/ 148 hp and 145 lb-ft torque [XV Crosstrek and Impreza]
2.0 liter 4 cyl DOHC engine w/ 200 hp and 151 lb-ft torque [BRZ]
2.5 liter 4 cyl DOHC engine w/ 173 hp and 174 lb-ft torque [Forester, Outback, Legacy]
2.0 liter 4 cyl DOHC turbocharged engine w/ 250 hp and 258 lb-ft torque [Turbo Forester]
2.0 liter 4 cyl DOHC turbocharged engine w/ 268 hp and 258 lb-ft torque [WRX]
2.5 liter 4 cyl DOHC turbocharged engine w/ 305 hp and 290 lb-ft torque [STI]
3.6 liter 6 cyl DOHC engine w/ 256 hp and 247 lb-ft torque [Outback, Legacy all Tribecas]

Subaru firmly believes that the Horizontally-Opposed Engine is the optimum design for driving enjoyment. The pistons face away from each other in a 180º symmetrical layout around the crankshaft and work to balance out each other's vibrations, delivering a smooth, shudder-free feel. This is because the engine can rotate freely at any given speed, delivering heart-gripping response to the driver. The length and height of this engine layout can be kept shorter than a traditional in-line engine, and it is also lighter. The engine can be mounted lower in the vehicle than other engines, and weight balance on the left and right can be made almost exactly the same. In this design, the low center of gravity engine lowers the center of gravity of the entire car. Similarly, a symmetrically balanced engine increases the symmetrical balance of the entire car. Both of these aspects combine to deliver a safer, more stable, and ultimately, more enjoyable experience on the road.

The new generation BOXER engine, FA20, now comes mounted with Subaru's first direct injection turbo. This helps raise the anti-knock limit and provides more precise fuel injection control, resulting in a higher compression ratio and greater efficiency that could not be attained with previous turbo engines. The 2.0-litre delivers power rivaling that of much larger capacity turbo engines for truly exceptional sports performance, yet comes with unbelievably low fuel consumption and exhaust gas emissions. True on-road performance befitting of a sporty, next-generation power unit.

With the new-generation BOXER engine used as the basis for design, engineers focused on developing a new NA engine with the aim of delivering high power output and environmentally-friendly performance, combined with the benefits of a low centre of gravity. A square bore and stroke layout has been combined with D-4S next-generation direct injection technology to deliver an impressive 100PS per litre power output, all with lower fuel consumption and exhaust gas emissions. The classic BOXER sound can still be felt in all its glory from within the cockpit, in a design that has been engineered to maximize the fun that the BOXER delivers.

To meet the constantly changing needs, a completely new BOXER engine was engineered from the ground up, with new enhancements across the board being implemented. A longer stroke and more compact combustion chamber combine with a dual AVCS for better intake and exhaust efficiency, lighter pistons and reduced friction throughout the engine, bringing exceptional efficiency and impressive performance. Mountains of low-speed torque mean exciting acceleration response, making the engine easier to handle in day-to-day driving. It's an engine designed for both environmental responsibility and fun, in what can only be called a new-generation powerhouse.

The world's first commercial Horizontally-Opposed Diesel Engine developed for passenger vehicles is the SUBARU BOXER DIESEL. When petrol engines are converted to diesel, strengthening of the engine block usually makes the engine bigger and heavier. The SUBARU BOXER, however, was originally designed with rigidity in mind, allowing the 92.0 mm x 75.0 mm bore and stroke of the 2.0-litre petrol four-cylinder engine to be changed to a square 86.0 mm x 86.0 mm design. The result is a more compact combustion chamber and greater fuel efficiency, and combined with a higher pressure common rail fuel injection, an improved oxidizing catalyst with closed Diesel Particulate Filter (DPF), a variable nozzle turbo and electric power steering, these all help to reduce fuel consumption and CO2 emissions. Ceramic glow plugs also quicken starting in cold weather. And whilst meeting the ultra-clean EURO5 emission standards, the engine delivers even more torque compared to previous models. A prodigious 350-Nm of peak torque is delivered at a lower 1,600 rpm - providing smooth, free-breathing performance at any speed. These advantages are evidence of the vision that Subaru has in using the Horizontally-Opposed Engine.

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