Two types of engine layout

Once you have learned the keywords related to engine performance, it’s important to know about engine types. In a car catalog, the information available often includes the number of cylinders, the cylinder layout and the valve train type for intake and exhaust of the air/fuel mixture.

●Cylinder Layout

Power sources for cars are beginning to diversify due to the advent of hybrids and EVs, but the mainstream is still petrol and diesel engines – all of which fall under the category of 4-cycle reciprocating engines. A 4-cycle engine is so-named because of the four cycles it goes through in its reciprocating process; intake - compression - combustion - exhaust.

In an automobile engine, multiple cylinders and pistons are combined to produce large amounts of power. The combinations include 3-cylinder, 4-cylinder, 6-cylinder, 8-cylinder and 12-cylinder (and so on). There is also a variety of different cylinder layouts, such as inline, V, horizontally opposed and W.

●Valve Train Type

A 4-cycle engine has intake valves, which open during the intake stroke to draw in the air/fuel mixture, and exhaust valves, which open during the exhaust stroke to let out the exhaust gas. These valves are located on the combustion chamber at the top of the cylinders; they open and close in a timed manner to either seal or open the combustion chamber. In engines tuned for power or fuel economy, quite often there are multiple intake/exhaust valves, with usually three or four valves per cylinder.

The opening and closing of valves is performed by a part called a cam, which rotates in sync with the engine. There are a few different types of cam setup, such as DOHC, SOHC and OHV. In modern engines, the valve open/close timings and amount of valve lift are controlled by computers to enable more efficient valve control.