Engines and their layout Passenger cars can be either gasoline engines or diesel engines. Due to the high thermal efficiency of diesel engines, good fuel economy, and long service life, there is a tendency to switch gasoline engines to diesel engines. Passenger cars equipped with diesel engines have large power and widely use open combustion chambers, turbochargers and exhaust gas purification and noise elimination devices.

There are three main engine layouts: 1 The front engine is placed above the front axle. 2 The engine is placed in the middle, lying under the floor, between the front and rear axles. 3 After the engine, the engine is placed in the rear of the vehicle. This arrangement can be further divided into three forms, namely the vertical layout of the vertical engine, the vertical layout of the vertical engine and the horizontal engine under the floor. The rear engine position makes exhaust gas and noise difficult to pass into the passenger area. At the same time, this arrangement can make the front and rear axle load distribution reasonable. Since there is no longitudinal transmission between the front and rear axles, a luggage compartment with a large volume can be installed under the floor of the carriage, so it is used by many countries in the world.