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2. 180 degrees would be a boxer engine (ie Porsche, Subaru) which is effectively a V engine with the ultimate obtuse angle.
3. There are actually two types of Rotary engines.
Wankel Cycle type engines use an eccentric central rotor and can't really be compared to a piston based engine. Effectively, a rotary could be considered a two-stroke engine with the three zones created by the rotor are a compression/exhaust stroke.
Radial engines are engines where the cylinders are arranged around a central point and radially arranged. Examples include some aero engines.
Each of the layouts has some inherent advantages and disadvantages.
For example, V engines tend to be compact longitudinally which reduces crank length and has advantages in packaging for a given displacement. Hence why this is used a lot in race engines and front wheel drive vehicles. Larger displacement engines also tend to use V arrangements for similar reasons. However, the V also has inherent balancing issues which are complicated by the angle of the V and the different axes of the cylinder banks.
Even different V engines can have different layouts first instance the flat plane crank V8 is effectively 4 sets of V twins mounted together compared to the more common V8 which is effectively two banks of inline 4 layouts.
Inline engines are inherently smoother particularly 6s which fire every 60 degrees of revolution in a 4 stroke. But are fairly long and have a higher deck height compared to other layouts.
Radial engines are great in propeller planes but the deck height makes them difficult to mount in a vehicle.
And flat engines are usually quite wide but can lower the centre of gravity.
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