Four cylinder engines - and - Six and eight cylinder engines.

Four-cylinder engines

This is perhaps the most popular engine for ordinary cars of medium size. The torque obtained, as compared to a single-cylinder engine, is much more uniform because two working strokes per revolution are obtained. Further, the balancing is also better. Apart from this, the maintenance is also easier as compared to the engines and is much more uniform because two working strokes per revolution are obtained. Further, the balancing is also better. Apart from this, the maintenance is also easier as compared to the engines with a larger number of cylinders.

The four cylinders are all in a line. The second and third cylinders are in phase, while cylinders 1 and 4 are also in phase, but in the direction opposite to 2 and 3. Thus the reciprocating forces are also nearly balanced.

Six and eight-cylinder engines

     

                          For higher h. p. and smoother torque, the six and eight-cylinder engines have been used. Like the four-cylinder engines, they have also been designed in the form of inline, v-type and opposed-type configurations. Whereas out of the six-cylinder engine types, the in-line type is most widely used, in the case of eight-cylinder engines, it is the v-type which is almost universally in use. The angle between cylinder banks is generally kept at 90^o. 

Its main advantages are:

The overall length of the engine decreases.

With 90^o v-angel, good engine balance may be achieved.

Even firing intervals are obtained.

Simple construction than the in-line type.

The disadvantages are that balancing is difficult and a more elaborate intake manifold is required from a central carburettor. V-engines are also more costly to manufacture because of the increased surfaces required to be machined.

            V-8 engines with smaller v angles, say 20^o, have also been made. The advantages of narrow v are less torsional vibrations and increased stiffness. However, the valve operating mechanism is complicated.