Cars and Tuning

The diesel engine receives east name because it is the last name of his inventor, Diesel the Rudollf German.
The diesel engines and the motors of explosion are motor thermal of internal combustion. The diesel engine also it is known him with the name of combustion motor.

To the gasoline motor him explosion flame, since one has seen previously, because, for its operation the force is used that produces the explosion of a mixture air-gasoline.
In the diesel engine, the force for its operation provides the expansion of the gases that take place when burning (combustion) a certain amount of fuel in certain conditions.
The used fuel is the gasohol (diesel oil).

Well-known the organization and constitution of an explosion motor, the one is known the combustion motor; the existing differences between both are mainly in the necessary elements for the preparation of the fuel and in the form to obtain to their inflammation (motor of explosion) or burned his (motor of combustion).
In the explosion motor the previous formation of a gasoline mixture was necessary pulverized with air, operation that is made in the carburetor. The one of combustion the air enters single the cylinder, injecting itself the pure diesel oil in the own cylinder. It does not use carburetor and difference in the entrance to the cylinder of the fuel and the supporter of combustion, with respect to the one of gasoline.
The inflammation of the mixture in the explosion motor is caused with an electrical spark that jumps at the moment adapted in the compression chamber, for which a system is needed ignition that produces it and distributes. In the one of combustion, the diesel oil is burned as it penetrates injected in the combustion chamber, without spark jump some.
The diesel oil in the combustion motors has to be sent to the compression chamber dosed as far as amount, to a high pressure and in a certain moment
Fuels
The fuel used in the diesel engines, is a product derived from petroleum. It is obtained in a process less complicated than the used one in the obtaining of the gasoline, by means of the distillation of gross petroleum between 150º and 300º. This fuel is a light oil and that is used in 5000 diesel engines that reach r.p.m.
Another oil, the fuel-oil or heavy oil, is used in diesel engines of great dimensions that reach about a 2000 r.p.m.
The characteristics that must reunite the diesel oil, among others, are the following ones:
or Good autolubricante power mainly for the injection system.
or Temperature of low inflammation, to facilitate the engine start-up and so that the combustion is made in the smaller possible time.
or Low point of freezing.
or the sulfur content nonsuperior to 1%.
or To be able calorific 10,000 kcal/Kg.
or Very volatile, to mix itself easily with the air.
or stable Viscosity.
or additive Content that facilitates the combustion (5% Ethyl).
or Stop cetane number.
The cetane number or cetanaje, expresses the facility that has the diesel oil for its pre-ignition or inflammability.
Organs of the diesel engine
They are similar, as far as form, to those of the gasoline motor, although the characteristics of the materials are different due to the concerted effort to that they are put under.
Block
The cylinders form a block of great size, of smelting or light alloy of aluminum. The cylinders are formed, generally, by humid shirts.
Butt
It is the element most characteristic of the motor of combustion in his difference with the one of explosion, since the compression ratio is very high in the diesel engines, must as well have a design that facilitates the spontaneous combustion.
At the end of the compression of the air, one is to a pressure next to the 40 kg/cm² and one temperature of 500 to 600º C, where when injecting itself the diesel oil is burned instantaneously. In those of explosion, at the end of the compression, rare time the pressure exceeds the 15 kg/cm² and the temperature 350º C. All these characteristics does that:
or the combustion chambers are smaller than in the case of the explosion motor.
or the cameras have different forms to facilitate the spontaneous combustion.
or the injectors for the feeding of the fuel in the cylinders are located in the butt and certain points for a perfect combustion.
These butts usually are of light alloy, such taking elements that those of the explosion motors (refrigeration, lubricates, distribution, etc.).
The cameras can later be made in the same butt or be adapted.
The union between the butt and the block of cylinders is made with a great number of special screws (internal pressures very elevated) and its corresponding meeting.
Crank
Due to the concerted efforts that receive, must make sure their rigidity and resistance. For it, it is increased to the number of supports, having one between elbow and elbow, five for 4 cylinders, seven for 6 cylinders (in line). One is used in his manufacture special steel of great tenacity.
Pistons
Normally they are of a very resistant aluminum alloy. They are longer than those of the motor of explosion and with greater number of compression rings and lubricates to assure better the closing piston-cylinder. The head of the piston has, sometimes, forms special to form the combustion chamber and to create eddy that improves the mixture of air/fuel, mainly they take some light cracks so that they do not trip over the valves when it is in the P.M.S.
Connecting rods
Like those of the motor of explosion, although more resistant and drilled of the head on the foot to lubricate the bolt.
Operation
Theoretical cycle
The motor of combustion, like the one of explosion, can be of two or four times, and can say that, this last one is used.
In the one of four times, just as in the one of explosion, every time is average return of the crank, constituting two returns of the crank the complete cycle. Only the third time is the one that carries out the work.

First time
Pure air admission, without mixture and, in general, great amount. The piston goes of the P.M.S. to the P.M.I.; the admission valve remains open and the one of closed escape. The full air cylinder.
Second time
Compression of the air, that is in the cylinder, being reduced to the volume of the compression chamber.
With a compression ratio that oscillates between 18 and 24 to 1, it supposes at the end of the compression, a pressure around 45 kg/cm² and one temperature of 600º C. The piston is had displaced of the P.M.I. to the P.M.S. and both valves remain closed.
Third time
Combustion (autocombustión of diesel oil). Having the air to a pressure and suitable temperature, a diesel oil spurt is introduced in the compression chamber, to great pressure, that pulverizes it and mixes with most possible one of the air. This air warms up the fine drops of diesel oil, elevating its temperature until this one begins to burn itself. The gases dilate in the compression chamber, takes place an extraordinary increase of pressure. This pressure, that only finds like movable point the head of the piston, loads on him all the force, forcing to him to descend abruptly from the P.M.S. to the P.M.I. being constituted the motor time.
The piston has gone of the P.M.S. to the P.M.I and both valves remain closed.
Fourth time
Escape. It is just as in the explosion motors. The piston expels gases burned to the outside leaving the cylinder prepared for a next cycle.
The piston is had displaced of the P.M.I. to the P.M.S. the admission valve remains closed and the one of open escape. Of this form the cycle finishes and the crank has given two returns.
As they summarize they can emphasize the following comparative points between the motor of explosion and the diesel engine or combustion:
or the compression ratio is included/understood between 18 to 1 and 24 to 1. (Much greater than in an explosion motor that arrives up to 10 at 1).
or During the admission, the motor inhales only the air. The one of explosion inhales mixture air-gasoline.
or the injection must become to very high pressure. In the one of explosion one becomes inflamed thanks to the electrical spark.
or the fuel becomes inflamed by pre-ignition and lasts the time that lasts the fuel injection. In the one of explosion the combustion is very fast.
or In the compression very high temperatures are reached great pressures (up to 45 Bars) and (600º C).
or the combustion is made to constant pressure. In the explosion motor it is made to constant volume.
Mixed cycle
At the present time the mixed cycle is used, in which the combustion later takes place first a constant volume and to constant pressure.
This is obtained modifying the system of combustion in different designs from the cameras, that during the compression, create turbulence in the air to the compressed being who maintains the uniform temperature in all the points of the camera. Of this form, when injecting the fuel, the mixture with the air takes place with greater rapidity and uniformity, and consequently, it increases the burning rate of the same one.
Like in the motor of explosion, and due to the same reasons, in the diesel engine settings in the distribution levels take place to obtain a greater yield of the cycle (practical diagram). These levels can be greater than in the explosion motors, soon also it will be it the valve overlap, because it does not matter that something of air escapes if with them a better sweeping of burned gases is obtained.
Next the diagram of distribution of motor imagines (turns of the crank)
1, Time of admission.
2, Time of compression.
3, Time of combustion.
4, Time of escape.
A.A.A. Advance opening admission valve.
R.C.A. Delay closes admission valve.
A.A.E. Advance opening escape valve.
R.C.E. Delay closes escape valve.
A.P.I. Advance injection principle a=27º

Fig.2
Systems that complement it
System of lubrication or lubricates
The elements that compose the systems of lubrication are such that an explosion motor, with the same disposition of these and operation. The used system more is the one of impact pressure, that at the present time is also applied in explosion motors.
Where it varies the diesel engine is in the conditions of lubrication that will be much more hard that in a motor of explosion due to the elevated compression, reached pressures and operating temperatures.
On the other hand, due to the friction, the oil is put under other disadvantages:
or When existing a number greater of segments and greater length of the pistons, the resistance to slide are greater.
or sulfur that contains the diesel oil hardens and makes difficult so much the action of the segments like the sliding piston-cylinder, affecting to him to its elasticity.
All these factors must be reduced of the following way:
or Using a suitable oil: of excellent accredited quality and. Detergent oils “HD” are used; recommended by the manufacturer.
or System of suitable filtrate and in good state and of the best qualities.
or more frequent Maintenance: the capacity of the circuit of lubrication in volume is much greater than the one of a gasoline motor, but the changes of oil and filter are much more frequent that in an explosion motor (until half of the time). The instructions of the manufacturer are due to follow.
or Equipping the circuit of an oil radiator to cool the lubricant of the circuit, mainly in motors that are put under great exigencies.
System of refrigeration
Because of the high temperatures, specially in the butt, the refrigeration of a diesel engine has to be more precise that in an explosion motor. Although there are the diesel engines air cooled, most abundant and more using are cooled by liquid.
The used system is the one of liquid refrigeration forced by pump, equipped with electroventilador and hermetic circuit to pressure.

The differences of the system with the explosion motor are:
or Greater capacity of the circuit, since the refrigeration has to be more effective.
or Greater size of its organs: greater ventilator, greater size of the radiator, pump of more volume and the water boxes of greater dimensions.
or more frequent Maintenance more meticulous and, since the diesel engine is more sensible than the explosion motor; therefore the refrigeration system must be always in perfect state.
System of distribution
Because the diesel engines do not reach the same number of revolutions that the explosion motors, a direct drive of the valves by means of a camshaft in head is not necessary, that would increase in price much the butt, although at the present time, mainly in tourism motors, it is being used.
In the diesel engines one resorts to a distribution with valves in head, commanded, generally, by balance beams with the camshaft somewhat elevated in the block so that the pushers are not so long; the camshaft takes several supports and is moved or by gears, dentated strap or chain.
The valves are similar to those of the explosion motors, although they require greater refrigeration reason why those of escape they are hollow and they fill up to them with sodium (with great coefficients of transmission of the heat).
In some cases, those of admission they take a baffle plate in the internal part of the head, with the mission to print to the admission air a revolving movement, that during the compression becomes eddy on which the diesel oil pulverizes and scatters better.

Given the great piston displacement of some diesel engines, sometimes, it is equipped to them with 2 valves of admission and 2 of escape, since if were not thus, the valves would have much so large and weight, with which its inertia would be very great (difficulty to open themselves and to close themselves).
System of cold start
The diesel engine does not need system ignition, since the inflammation of the mixture does not take place by spark, but by pre-ignition the fuel due to the high compression the air and to a later injection fuel.
Which it has the diesel engine is of a heating system so that the inhaled air takes an initial temperature that facilitates the engine start-up.
This section is explained with thoroughness in the following subject.
Even so, we can advance that, in a diesel engine are not used the carburetors, but the injection of the diesel oil.
The injection similar to the one of the gasoline, can be of two types:
or Mechanics, that but is used mainly in trucks.
or Electronics, less used by its price. One is used in diesel engines of high benefits.
The feeding system has two circuits, as we will see in the following subject:
or Circuit of low pressure.
or Circuit of high pressure.

Differences in its manufacture
Motor of explosion
or simpler Construction.
or Design of the normal fuel camera.
or simpler Manufacture in forms and resistance.
Motor of combustion
or heavier and complex Construction.
or Design of the camera or systems of complex combustion.
or more complex Manufacture as far as resistance of materials and designs in: butt, block, pistons, connecting rods, crank and segments.
Advantages and disadvantages
In this section we are going to enumerate some of the advantages and the disadvantages that present/display the diesel engines with respect to the explosion motors.
Advantages
or Greater thermal efficiency (more amount of heat transformed into work, on 35%).
or Less fuel consumption (on 25%).
or Minor price of fuel, at the present time.
or difficult fire Danger in case of failures or accidents.
or Minor atmospheric contamination, since the exact amount of fuel does not take place monoxide of carbon (CO) when injecting itself.
or more regular motor Pair based on the number of r.p.m. the almost flat curve.
or more lasting Motor (less revolutionized).

Disadvantages
or greater Weight. This implies more rigidity of the chassis and more resistant elements of suspension.
or Greater cost of acquisition (equipment of expensive injection and reinforced and sobredetermine the proportions elements and of better qualities in the used materials).
or Minor power to piston displacement equality.
or noisy Motor, specially in cold.
or expensive Repairs, better qualities of its components and skilled labor.
or Starting that requires some system of aid (heating of the induction manifold, resistance or spark plug of heating in the combustion chamber).
or more frequent Maintenance, always taking care of the instructions of the manufacturer.
or Vibrations greater than the explosion motors (greater effort).
or Minor to be able of acceleration. Diésel slow, its regime is smaller of 1500 r.p.m. and the fast diesel engine, its 4000 regime is of r.p.m., like average term.

DIESEL ENGINES

Definitions.

Caliber.
The caliber is the inner diameter of the cylinder measured in millimeters.
The caliber of the cylinder determines the air volume available for the combustion.
Race.
It is the distance that the piston in its alternative movement crosses, measurement between the his lower point and highest.
Piston displacement.
It is the total volume swept by the pistons.
In order to calculate the piston displacement, we multiplied the diameter of the cylinder by itself, and by a constant and the result we multiplied it by the race. This value we multiplied it by I number of cylinders of the motor and we obtain the piston displacement.
Compression ratio.
It is the relation between the maximum volume of the cylinder (cylinder o’clock inferior dead) and the minimum volume (cylinder in the top dead center). The compression can change, any air flight of the combustion chamber, for example, air that escapes by inserted of valves or the ring of piston, will reduce the compression in that cylinder.
If the maximum volume between the piston, in the bottom dead center, and the butt is of ten centimeters cubical and the minimum volume, the piston in its top dead center, is of a cubical, then centimeter the compression ratio would be of 10:1.
The compression ratio in the diesel engines usually is from 16:1 to 18:1.
In the gasoline motors usually it is from 7:1 to 12:1, this relation is limited not to cause pre-ignition.
The diesel engines reach temperatures of 540ºC during the compression, reason why pre-ignition would take place if the air with the fuel like in the gasoline motors were mixed. These motors air only enters the cylinder the compression race, the fuel is injected in the camera at the moment at which the cylinder is arriving at the top dead center.
Since the temperature of ignition of the diesel fuel is of 450ºC and the camera at the moment of the injection has 540ºC, the spontaneous combustion of the mixture of spark like in the gasoline motors takes place with no need.
Turbocompressor.
It is the element of the motor that compresses the air of the admission so that the cylinder with more amount fills up, with which it obtains to a greater power and yield. It consists of two turbines, the one of impulsion that takes advantage of gases exit of escape of the motor to move the one of compression that impels the air towards the cylinders.
Posenfriador.
As I disturb when compressing the admission air produces a heating in the same one, elements are used habitually to cool it, since when cooling it it diminishes of volume and it enters more amount the cylinder. It can have several systems of refrigeration like air-air, air-water, etc.
Thermostat.
It is a temperature regulator that helps to that the motor is warmed up more quickly, so that the normal temperature of operation is reached before, soon contributes to maintain it stable by means of its opening or closes to turn aside the flow of coolant to the radiator.
Oil coolers.
They maintain the temperature correct of the oil of the motor. They can be of oil-water or oil-air.
Cork of the radiator.
It is the element that maintains the pressurization of the refrigeration system. It is important to maintain it in good conditions, since it can give rise to very serious failures of the motor. Any doubt in its operation requires a change of the same one.