Engine Design & Classification

Engine Design & Classification: How automotive engines are categorized?

Engine Design & Classification:

An engine is a power generating machine. It converts potential energy of the fuel into heat energy and then into rotary motion. An automotive engine which produces power also runs on its own power. Overall, the manufacturers classify the engines according to their varied designs, constructions, and applications. Generally, automotive applications have following sub-categories, by which; different engine design vary from one another.

Automotive Engines are generally classified according to following different categories:

  1. Internal combustion (IC) and External Combustion (EC)
  2. Type of fuel: Petrol, Diesel, Gas, Bio / Alternative Fuels
  3. Number of strokes – Two stroke Petrol, Two-Stroke Diesel, Four Stroke Petrol / Four Stroke Diesel
  4. Type of ignition such as Spark Ignition, Compression Ignition
  5. Number of Cylinders – From 1 to upto 18 cylinders (in a car)
  6. Arrangement of cylinders which are Inline, V, W, Horizontal, Radial
  7. Motion of Pistons which are Reciprocatory, Rotary
  8. Size / Capacity
  9. Bore-to-Stroke Ratio
  10. Engine cooling methods such as Air-cooled, Liquid-cooled (Water based), Oil-cooled (Oil is cooled separately)
  11. Breathing such as Naturally Aspirated, Turbocharged / Supercharged
  12. Applications such as Bikes, Passenger Cars, Racing cars, Commercial Vehicles, Marine, Agricultural equipment and Earth-moving equipment etc.

The conventional automotive engine consists of following parts:

  1. Engine Cylinder Head – Houses camshaft (in case of OHC design), inlet valves, exhaust valves, inlet manifold with turbocharger (if fitted), exhaust manifold
  2. Engine Cylinder Block – Houses main engine parts such as pistons, crankshaft, camshaft, oil pump, oil filter, oil cooler, water pump and oil pan
  3. Alternator, A/c compressor, Power Steering Pump
  4. Flywheel, Clutch assembly, Clutch housing, Transmission

According to the arrangement of cylinders, an engine is classified primarily into following categories:

  1. Inline
  2. ‘V’ shaped
  3. ‘W’ shaped
  4. Flat / Horizontally opposed
  5. Opposed Pistons
  6. Radial

However, most commonly used engines in automotive applications are Inline, V, W, and Flat engine designs.

InLine Engine:

This type of design is a very basic and conventional engine design. In this engine construction, the cylinders are in a single straight line. An inline engine is used with 2, 3, 4, 5, 6 or upto 8 cylinders. Read More.

‘V’ Engine:

This is a newer generation engine design. In this engine construction, the cylinders are at an angle. The angle between the cylinders form a 'V' shape and that is why it is a 'V' engine design. Read More.

‘W’ Engine:

In this engine construction, the engine has three rows of cylinders placed at an angle. The angle between the cylinder rows form a 'W' shape and that is why it is a 'W' engine design.

W Engine Design
W Engine Design

Typically, it is used in high-speed racing cars. The cars with 18 cylinders are some of Bugatti show cars - EB118 concept, EB 218 concept, 18/3 Chiron concept - all with an 18-cylinder ‘W-18’ engine and EB 18.4 Veyron Concept - with a 16-Cylinder ‘W-16’ engine.

Watch Bugatti Veyron W16 Engine Animation here:

Flat / Horizontally Opposed:

The main advantage of flat / horizontally opposed engines is that it allows a lower center of gravity, thereby helping in improving the vehicle performance. This type of engine is used in Subaru cars.

Flat / Horizontally Opposed Engine
Flat / Horizontally Opposed Engine

All Subaru models such as Impreza, Forester, Tribeca, Legacy, Outback, Baja, BRZ and SVX use either a flat-four or flat-six engine.

Watch Flat Engine Animation Here:

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About Shirish

Shirish is a technical consultant & blogger with experience of over 20 years in the automobile field. He regularly publishes specific technical articles on automotive technology. When not writing a blog, he wanders in nature or goes on long-distance motorcycle rides.

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