A Boxer or "Flat" engine is any engine where the cylinders and pistons are arranged in two separate banks, 180 degrees apart. Also known as horizontally opposed engines. Ferrari's 1980's Testarossa had a Boxer 12 cylinder engine. The term Boxer comes from the action of the pistons resembling that of a punching boxer.

Boxer engines have several distinct advantages:
1. A low centre of gravity
2. Compact dimensions
3. The piston forces are balanced,negating the need for heavy and complex counter-balancing shafts.
4. Increased crankcase rigidity
5. Stiffer, less expensive to engineer, crankshaft

An inherent disadvantage of the Subaru (and Porsche layout for that matter) is that the AWD systems needs to be located in a longitudinal orientation behind the the engine flywheel. This means that in a Scoob, the engine will always sit in front of the front axle and in a Porsche, behind the rear axle. This increases, among others, the polar moment of inertia. In plain and simple terms, Subarus are nose-heavy and Porsches are arse-heavy.

The many benefits of the engine and transmission layouts, however, outweigh the above compromise.

The primary consideration when it comes to engineering a 4 wheel drive Cayman is the complexity, extra weight and cost of creating an AWD system to work with a Boxer engine in a mid-mounted application. (See my earlier post on this...)