Air Fuel Ratio

For many automobile engines, the term block is interchangeable with engine in this context, for example V block and V engine can often be used interchangeably in American English. This is because the most common forms are all based on a combined engine block and crankcase that are milled from a single piece of cast metal. The locations of the major components are largely determined by the shape of this one component.

The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V engine do not in any way form a V, but it is regarded as a V engine because of its crankshaft and big end configuration, which result in performance characteristics similar to a V engine. But it is also considered a flat engine because of its shape. On the other hand, some V-twin engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen VR6 engine is a hybrid of the V engine and the straight engine, and can not be definitively labeled as either. The names W engine and rotary engine have each been used for several unconnected designs. The H-4 and H-6 engines produced by Subaru are not H engines at all, but boxer engines.

Engine types include:

Single cylinder engines
Inline engine designs:
Straight engine, with all of the cylinders placed in a single row
V engine, with two banks of cylinders at an angle, most commonly 60 or 90 degrees.
Flat engine, two banks of cylinders directly opposite each other on either side of the crankshaft.
H engine, two crankshafts.
W engine. Combination of V and straight, giving 3 banks, or two V's intertwined giving 4 banks.
Square engine.
Opposed piston engine, with multiple crankshafts, an example being:
Delta engines, with three banks of cylinders and three crankshafts
U engine, two separate straight engines with crankshafts linked by a central gear.
X engine.
Radial designs, including most:
Rotary engine designs. Mostly seen on pre-WWII aircraft.
Pistonless rotary engines, notably:
Wankel engine.