Four-stroke Diesel Fuel Injection Motor

Motor quatro tempos ciclo Diesel - Four-stroke engine Diesel cycle - Motor de cuatro tiempos ciclo de Diesel
Interactive animation demonstrating the relation between the various systems of an internal combustion engine with fuel injection ignition that develops the Diesel cycle and plots in a diagram Pressure x Volume idealized approximations of the curves of the theoretical Diesel cycle, allowing us to study the system with ease.

This type of engine uses as fuel: light and heavy fuel oils (derived from petroleum; the ambient pressure and temperature are not flammable); Oil etc.
– You can stop the animation, or lead to a certain point, drag and drop the diagram pointer that marks the four cycle times, this action will display more information and handouts;
– Keep rolling the page and go to a summary table to understand the theoretical aspects of engine operation the fuel injection deisel / autoignition.

Four-stroke Internal Combustion Engine and Self-Ignition Injection Diesel Fuel

Theoretical description of a four stroke engine running on diesel fuel

Time Name Description of the process Valve
Admission Escape
1 Admission
With the -plunger- piston at TDC dead  – upper dead point – the valve control opens the intake valve, the inertia of the crankshaft moves the piston rod that pulls the piston towards the lower dead point PMI. Moving the piston reduces the pressure in the combustion chamber, the top of the cylinder, and the created vacuum sucks the air with practically no pressure change. The cylinder volume is filled with air-oxygen-filtered atmosphere, with pressure of approximately one atmosphere.

The cylinder volume is filled with air from the atmosphere -oxygen- filtered with approximately one atmosphere pressure.

Opened Closed
2 Compression
With the piston at BDC the inlet valve closes and the crankshaft, which continues to turn, pushes the piston TDC way to compressing the air in the combustion chamber without thermal energy exchange with the environment. The compression ratio is very high and part of the mechanical energy of the piston, and the kinetic energy of the particles, is transferred to the air by increasing its thermal energy and its pressure to a point that allows ignite the fuel.

Some degrees of crankshaft rotation before the piston reaches TDC some system injects fuel – delay of ignition-, in aerosol form, which volatilizes into the superheated air and PMS starts burning. The fuel volatilization process requires some time, therefore the injection occurs at the end of the second time.

Closed Closed
3 Only one that provides mechanical


The ignition of the fuel occurs by self-ignition and combustion of diesel is relatively fast, increasing the pressure and temperature inside the combustion chamber without increasing its volume at the first time, but keeps burning fuel, Closed Closed
The steadily constant expansion forces the walls of the combustion chamber, including the piston head, and increases the volume of the upper cylinder to force the piston displacement. The pressure and temperature inside the cylinder do not change forcing the rotating crankshaft to provide torque.
With the piston stroke, the chemical reactions that contribute to the maintenance of pressure begin to reduce and there is a drop in pressure -at increased volume- without exchange of thermal energy inside the cylinder.
Thermal energy transfer
With the piston approaching the PMI, the exhaust valve begins to open, the gases resulting from the combustion, which are in pressure and temperatures higher than atmospheric, quickly escape to the exhaust manifold and the pressure in the cylinder falls into a atmosphere.

The third time is the only one that provides mechanical power to the engine cycle.

Start of opening
4 Exhaustion
With the piston in the PMI, and the open exhaust valve, piston, moved by the inertia of the crankshaft, resumes his way to the PMS cylinder expelling the gases from the combustion, virtually no change in pressure.

Just before the drum reaches TDC the inlet valve begins to open, the temperature difference and density of the gas admission and exhaust, and the inertia of the gases, drag the remnant of exhaust gases to the exhaust manifold .

The exhaust valve closes in preparation for the resumption of the four-stroke cycle.

Closed Opened
Start of opening Start of closing
Eduardo Stefanelli

Engenheiro por profissão, professor por vocação