While it isn’t new technology, it’s one of the more misunderstood: Subaru’s famous “boxer” engine and Symmetrical All-Wheel-Drive. Just about everyone’s heard the terms, but aren’t sure exactly what they mean.
“We’ve been using the boxer engine since 1965,” says Peter Johnson, product specialist for sales training for Subaru Canada.
“Every engine that we sell in North America is a boxer.”
Also called a “flat” or “pancake” engine, a boxer engine’s pistons lie flat on either side of the crankshaft, unlike an inline engine, where they’re upright, or a V engine, where they’re slanted on either side of the crankshaft in the shape that gives the engine its name, as in V6.
“There are key advantages to having a boxer engine,” Johnson says. “It sits lower in the vehicle than a conventional engine so there’s a lower centre of gravity for better handling. There are better aerodynamics, because the hood line can be lower. There’s improved passive safety: because the engine sits on a downward angle, it “submarines” under the passenger compartment in a severe collision. It’s also lightweight, and that improves handling, braking, acceleration and weight distribution.”
Boxer engines are also inherently smoother, because the pistons on one side counteract the vibration of pistons on the other. Other engines usually contain a balance shaft to offset the piston vibration; boxer engines don’t need this heavy extra part.
The boxer engine is a key part of Subaru’s Symmetrical All-Wheel-Drive – which isn’t, as many people think, an equal amount of power going to each wheel. Rather, it describes the system’s symmetrical design.
“If you had a bird’s-eye view of our drivetrain, you could cut it down the centre and fold it over itself,” Johnson says.
“The left side is equal to the right.” The balanced design and lower centre of gravity improve the car’s handling.
Many modern cars have transverse engines, which sit sideways in the engine compartment, with their transmissions mounted on the side. Because of this, the left and right front axle shafts — which transfer power from the engine and transmission to the wheels — are different lengths. This can result in undesirable characteristics on front-wheel-drive vehicles, such as torque steer, where the car pulls to one side on hard acceleration due to the uneven shaft lengths.
Subaru engines are longitudinal, facing front to rear, with the transmission connected at the back of the engine.
“The advantage is that you have a long-travel front suspension, because you have equal-length axle shafts, and that absorbs road irregularities better,” Johnson says.
“You also have a tighter turning radius, which is great in urban settings. It’s all very effective and very efficient.”