Cars and Tuning

Mission of the refrigeration system
When speaking of the explosion motor we said that in its operation part took advantage of the existing chemical energy in a fuel and that it was transformed into mechanical energy.

The transformation became by means of the inflammation of the mixture that produced an explosion. In this explosion an extraordinary heat is developed, until the point that most of the energy that is not used, yes gives rise to the heating and therefore to very elevated temperatures in the elements and pieces of the blasting chamber, mainly during the time of escape.
This temperature, that at the moment of the explosion approaches the 2,000 degrees (instantaneous temperature), would produce an expansion so, that the pieces would get to bind tightly themselves, giving rise on the other hand to a decomposition of the lubrication oil.
However, heat in the compression chamber not only takes place, but also in the cylinders, because even though in them the explosion does not take place and they are not put under the instantaneous temperature that this one causes, yes are it to the one of gases during the time of explosion and on the other hand to the heat produced by the continuous frotamiento of the piston on his walls.
In order to eliminate that heat partly and to avoid the damages that can cause it resorts to the refrigeration of the pieces or elements of the motor that more heat receives. It is obtained with the refrigeration system.
This absorbed heat very little has to be neither (since it would produce expansions), nor very elevated (because it would lower the engine efficiency remarkably). Approximately a 30% of the heat produced in the explosion or combustion will be eliminated by the refrigeration system.
In addition to these great expansions, the high temperatures produced in the motors cause that the amount of mixture that arrives at the cylinders is small, reason why is necessary for the increase of engine efficiency, to equip it with a system with refrigeration. Also it happens that, due to the high temperatures, the lubrication oil loses its lubricant properties. The parts that will require greater refrigeration, will be those submissive more high temperatures. These are: the butt (specially the zones of proximity to the escape valve), the valves (with its seats and guides) and the cylinders (due to the rubbing with the piston).

Systems of refrigeration
The refrigeration systems that are used at the present time are:

Air cooling.
Liquid cooling.
Air cooling
The air cooling is obtained exposing the hottest parts of the motor (butt and outside of the cylinders) to the airflow that takes place by the march of the vehicle or by a turbine, when continuous going away renewing and quickly the air absorbs the heat of the surfaces before indicated.
The heat produced in the motor evacúa directly to the air, for which the motor is constructed of light alloy (with good coefficient of thermal conductivity) and the faying surface is increased to him with the air, equipping itself to him with a series of fins. These whichever fins will be greater greater is the heat to evacuate. Thus, then, the greater ones will be nearest the butt (blasting chamber).
The heat interchange between the cylinders and the air will be greater at the most thin are the walls of the fins, being due to maintain the space between the fins perfectly clean.
Depending on the form to make arrive the air at the cylinders two types of air cooling exist:
or direct Air cooling.
or forced Air cooling.
Direct air cooling
The air that affects the vehicle when circulating, as well, cools the motor, depending therefore the refrigeration on the speed of the vehicle and not on the one on the motor.
To the slow motion, the refrigeration is minimum, since it is made solely by radiation and to low revolutions of the motor. For that reason it is only used in motorcycles of small piston displacement that have the motor exposed to the air.

In tourism and trucks he would be totally ineffective, since the heat elimination by radiation within the motor compartment would be minimum.
Forced air cooling
The air cooling of the motors, when being these closed generally by the body, is necessary to channel the air, canalizing it towards the cylinders and butt.
It is had a turbine that activates and increases that current, that is moved by a strap mounted in a pulley located in the end of the crank. The ventilator inhales the outer air and it directs it to the parts to cool.
An automatic strangler regulates the air passage based on the necessities of the motor. Thus, in the cold start, it cuts the air passage and the motor will reach its temperature of regime quickly.
Advantages
or Design and simplified construction.
or Little weight of the motor (it does not have elements like radiator, sleeves or pump).
or Minimum entertainment, when lacking cooling liquid, pump or sleeves.
or small Size of the motor, when not having camera for liquid.
or Greater thermal efficiency (less losses of heat by refrigeration).
or the temperature of optimum regime of the motor before in the liquid refrigeration is reached.

Disadvantages
or irregular Refrigeration, because it depends on the temperature of the air, the altitude and the speed of the vehicle.
or They are noisier, because the air when happening between the fins produces vibrations.
or they cool off very quickly (use of the strangler quite often).
or Worse filled of the cylinders (smaller useful power), due to the reached temperatures.
or it is used in motors to bóxer or of opposed cylinders, to canalize better the air.
Liquid cooling
It is the generalized system that uses the present automobiles.
In this system cylinders and block of cylinders they constitute an envelope in whose interior the refrigeration liquid circulates. The cooling liquid also circulates around the interior of the butt through hollows anticipated to the effect (liquid cameras).
The cameras uniformly are distributed around the combustion chamber and cylinder. This liquid, that is warmed up to the contact with the walls, next is directed towards the radiator, where it yields his heat to the ambient air, to return later to the block of cylinders.
The heat capacity of the liquid very is elevated, being, sometimes greater than the one of the air. For that reason, the volume of the liquid cameras, the cylinders and the speed of circulation of the liquid, must contribute not to let arrive the water until the boiling point.

Elements of the systems of liquid cooling
Next we described the component elements of a system of refrigeration by forced circulation of liquid:
or Water box.
or Radiator.
or elastic Unions.
or water Pump.
or Ventilator or electroventilador.
or Thermostat.
or Elements of control.
Water box
They are hollows practiced in the motor block and the butt. Around which the cooling liquid circulates. The parts surround that are in direct bonding with gases of the combustion (cylinders, combustion chambers, seats of spark plugs and guides of valves).
They are characterized by the liquid volume that circulates in the motor.

Radiator
Its mission is to cool the hot water coming from the motor. It is located, generally, in the front part of the vehicle so that the air affects him during its displacement.
The parts of the radiator are indicated in
It is united to the chassis of elastic form by means of tacos of rubber and by means of flexible sleeves to the motor, having thus avoided possible damages with the vibrations of the motor and the march of the vehicle. For his manufacture they are used generally, alloys with copper (brass).

Although it is not certain that whichever greater it is the frontal surface of the greater radiator will be also the refrigeration (more surface in contact with the air), agrees either that it is of an excessive surface, since of being therefore the motor would take much in reaching its optimal temperature of operation or it would not get to reach it. In some isolated cases blinds mount in the frontal part of the radiator to regulate the surface of the radiator exposed to the incidence of the air.
For that reason, the effectiveness of a radiator, depends on the exposed surface of the same one to the incidence of the air.
In order to improve the aerodynamic coefficient of the vehicle and that the surface of the radiator is sufficient, the heavy radiators instead of very high make.

The tubular radiator is formed by a series of cylindrical or flat tubes; fine lengths and; horizontal verticals or, surrounded by fins of great thermal conductibilidad that hold to him and simultaneously serve to him as cooling surface.

The air of the outside and the produced one by the ventilator pass among the tubes, absorbing the heat of its surfaces and with them the one of the water that by such descends.
The water falls horizontally vertical or and the air that penetrates horizontally cools it through the tubes that have a great conductivity.
In the honeycomb radiator the body refrigerator is formed by fine and short tubes with its ends widened in hexagonal form.
These tubes go soldiers an a others so that among them they leave a close space for the water, while the horizontal tubes are crossed by the air of the march.

The refrigeration surface is very great. Little they are used because of its elevated price.
In the superior part of the radiator it goes arranged a cork, that it can be watertight (modern system) or with safety valve (old system).
Water pump
In the refrigeration process, the circulation is activated by a pump that is put in in the circuit, between the low part of the radiator and the block, forcing the circulation of the cooling liquid (forced refrigeration).
The used pump more is of trowels of centrifugal type, that is to say, which the water that arrives at the impeller wheel, which tour within a bomb body of light alloy, is gathered by these and in his turn it expels it with force towards the periphery, forcing it to happen to the water boxes.

The pump goes installed frontal or laterally and receives its movement of the crank through the strap that in some cases also moves the ventilator.
In order to avoid that the water leaves by the axis, a device mounts to him type presses or frotamiento meeting, that is used at the moment.

The axis of the pump is mounted of eccentric form in the body of the same one, with object to save the water passage around the wheel.
One is due to verify and to review the state and the tension of the strap of the pump. If she is destensada the heating of the motor when sliding could take place this one. If very it were tightened it would affect to the bearings of the pump and the own strap to him.
Destensada must be neither very tightened nor, allowing a flexibility of about 2 centimeters, approximately.

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Elastic unions
The radiator is united elastically to the body (rubber heel) and to the motor by means of flexible conductions (sleeves) of such form that the vibrations do not harm the radiator.
Ventilator. Electro-ventilator
It is the element in charge to make pass an airflow sufficient to cool the water through the radiator. In addition it cools some external organs like generator, pump, pump of gasoline and carburetor.
In the old models the ventilator is mounted in the same axis that the water pump and while the motor works, it makes the ventilator. This causes that the ventilator works when the motor does not need it, that is to say, when the vehicle was cold or in march and to take advantage of the airflow produced in its route. This implies a consumption of energy, since at the moment the automobiles are, in its majority, of front motor, being able to take advantage of the current produced by the march.
At the moment the automobiles go equipped with a electroventilador with a thermoelectrial control, of such form that enters operation when acquiring the water of the circuit of refrigeration a certain temperature, thus avoiding unnecessary losses of power by drag in regimes in which the use of the ventilator is not necessary.
One of the elements of the electroventilador is the ventilator, that is a small helix, of two to six shovels. Whichever greater it is the number of these, more energetic will be the proportionate airflow; also it will be this more effective current at the most long are the shovels, until reaching a maximum in which it would begin to lose his effectiveness.
The shovels are made with laminae of steel, aluminum alloy or molded plastic. They must be the sufficiently solid thing so that they can absorb the deformations, as well as to be balanced well so that they do not produce vibrations.
The electroventilador enters operation when the temperature of the motor is superior to the one of regime, puts into operation the thermocontact that receives the temperature of the cooling liquid.
The thermocontact goes located, generally, in a low part of the radiator, or in the same butt.
When the vehicle is in march, the air affects the radiator directly, with which the refrigeration of the liquid is assured. When circulating at little speed, or when the vehicle is prisoner, the refrigeration in the radiator is smaller, and the temperature of the liquid will raise.
The electroventilador can go mounted ahead or behind the radiator. In anyone of the two cases, the sense of the air will be always of radiator towards motor (of it go to inside).

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Advantages
or Possibility of placing the radiator in the position that agrees more. This way it or behind the ventilator can be placed the radiator in the front of the vehicle, being the cross-sectional motor, as well as be mounted ahead.
or the march is quieter.
or the refrigeration, to the independent being of the vehicle and engine speed, avoids the overheat in case that the motor must work long time to slow motion.
or the motor consumes less for a same power, when not having to move the ventilator with the strap.
Disadvantages
or Although minimum, it is possible to review the greater complexity of the system, that increases the possibility of failures (the components of the electrical circuit).
Types of ventilators
At the present time ventilators are used that, only turn when the temperature of the motor rises until a certain degree.
Ventilator with electromagnetic coupler
It is provided with a magnetic clutch that is connected when the temperature of the water rises until a certain degree.
Ventilator with hydraulic coupler and thermal regulation by air of the radiator
The union between ventilator and the motor, are assured by a hydraulic coupler whose action is determined according to the amount of liquid that is introduced in him.
This liquid (oil of silicosa or hydraulic liquid), is contained in a cavity ready in the bucket of the ventilator or a separated deposit, and its introduction in the coupler is controlled by a valve to a bimetal fixed on the bucket of the ventilator and put under the temperature of the air flow that has crossed the radiator.
Ventilator with hydraulic coupler and thermal regulation by cooling liquid (viscous ventilator)
Its operation is based on the same principle that the previous one. It uses like friction element silicone, but the operation regulation is regulated by the action of the cooling liquid on the bimetal that acts in the step valve and not by the air that crosses the radiator.
Thermostat
Motor needs to be cooled, but as we said previously, not in excess, since a too low temperature produces a bad vaporization of the gasoline that is condensed later in the walls of the cylinders, mixing itself with the oil and diminishing its lubricant qualities, which causes greater cost of fuel and a worse lubrication.
Therefore we will need a device (thermostat) that causes that the refrigeration does not act when the motor is cold, so that the temperature of optimal yield is obtained quickly (this temperature, measurement in the refrigeration liquid, is of 85º to 90ºC approximately). This same device has to allow the complete or partial refrigeration of the water, depending on the temperature of the motor.
Therefore, the mission of the thermostat is to maintain the temperature of the motor in the one of optimal yield. For it the temperature acts on the passage of the water regulating of this one on 85º C. If an excess of refrigeration takes place (march at night to low temperatures), the thermostat becomes to close, warming up the motor.
In order to maintain the temperature of the motor, acting on the circulation of the liquid, a double shut-off valve is used (the thermostat), that is put in in the circuit of exit of the butt towards the radiator.
The thermostats that are used are apparatuses able to produce an action of mechanical type when it varies the temperature of the atmosphere where they are located, being used generally two types:
or Thermostat of bellows.
or wax Thermostat.
Thermostat of bellows
It consists of a closed metallic deposit, of very fine plate, with the walls in form of bellows or accordion. In this deposit there is a liquid or very volatile substance, like for example: ether, paraffin, etc.

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This valve, when the motor is cold, is closing the passage of the liquid towards the radiator and it allows it towards the pump. When warming up itself the liquid in the motor warms up the deposit of the thermostat with the volatile liquid, this one volatiza and is increased of volume. The deposit, by this increase of volume is extended, opening the valve and allowing the passage of the liquid towards the radiator, simultaneously that closes the passage towards the pump.
If, circulating with the vehicle, the temperature of the motor descends, by to be very low the outside, the liquid of the valve that was volatizado, its volume is condensed, diminished and the deposit is contracted, closing the valve the passage of the coolant towards the radiator and opening the passage towards the cylinders (through the water pump) until again the suitable temperature is reached.

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Wax thermostat
The operation of the wax thermostats is to simulate to the one of those of bellows, being replaced itself the volatile liquid by wax.

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This system is used at the moment.
Elements of control
The conductor must, at any moment, to be able to verify the temperature of the refrigeration water, in order to immediately detect the possible anomalies in the circuit of refrigeration or motor.
The control board is equipped to this aim; either with a luminous witness, or with a temperature indicator.
Luminous witness
The luminous witness ignites when the normal temperature of operation is not reached. When this operating temperature is reached, the lamp is extinguished, but it becomes to ignite if this one is excessive.
This luminous witness is sent by a thermocontact that is located in the butt or on the radiator.
The thermocontact is a device, that makes work the luminous witness to warn the conductor.
It is constituted by a bimetallic lamina that is become deformed based on the temperature. The deformation of this lamina establishes or cuts to the circuit of the lamp pilot.

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Temperature indicator
According to the precision of the apparatus, this one will be provided with a graduation, indicating the exact temperature of the motor, in zones of different colors, corresponding to an on-speed operation or abnormal.
These temperature indicators are sent electrically by a termistor that is located in the butt or on the radiator.
The termistor is a resistance that, based on the temperature, lets pass one more a current less intense. This variation of current makes turn aside the needle of the temperature indicator.

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Circuits of refrigeration
At the present time and general, one is used in vehicles automobiles, the refrigeration by closed or sealed circuit.
Another type of circuit, the one exists of open refrigeration that we will consider it as it bases of the previous one, although it is not used normally.
Open circuit
The filling cork of the radiator in its superior part has a safety valve. This valve communicates with the atmospheric pressure and its mission is the one to avoid that overpressures in the circuit do not take place. In case in the interior of the circuit of refrigeration an excessive pressure took place that could damage some of its elements, the circuit puts in contact with the atmosphere through the valve, taking place the evacuation of the internal steam to the outside and returning air to the interior of the deposit.
This system presents/displays the disadvantage of which the lost liquid is non-recoverable, with which there are to frequently control the level of the radiator to establish the losses.
In the 7 the component elements of the circuit are indicated.

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Closed or sealed circuit
This circuit consists of connecting the radiator with a small denominated deposit expansion glass. This way the liquid is not lost in the outside and can be recoverable.
The safety valve that allows the exit of the liquid of the radiator, is in the cork of closing or to the entrance to the expansion glass.

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This valve allows the passage of the water steam to pressure towards the expansion glass, (fig.18) until it is equaled with the pressure in the radiator. If the low pressure too much in the radiator, the valve allows the passage of the liquid of the expansion glass towards the radiator and restores therefore the pressure and the level in the radiator.

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The passage of the liquid between both elements is obtained by pressure differential of the element with more pressure towards the element with less pressure of the radiator to the glass or the inverse one.
The expansion glass communicates with the outside if the operation pressure is muy.superior.a the established thing and it does through the safety valve that takes the expansion glass.
The pressure in the radiator, is generally superior to the atmospheric one. Due to this pressure in the radiator, the boiling point of the liquid increases, that is to say, it boils to more of 100º C.
In this system losses of liquid do not exist. If there were them, we would have to review the circuit and to locate the point where the flight takes place to be able to correct it.
In the 0 the set of elements imagines that compose the circuit:

Cooling liquids
The water dealt with certain additives is used, like cooling liquid, due to its persistence of chemical agents, good conduction, by its abundance and economy.
The single water presents/displays great disadvantages like:
or calcáreas Salts that obstruct the canalizations of the circuit (hardness). It is corrected distilling the water.
or To temperatures of boiling he is very oxidating, attacking the circuit and its elements.
or Below 0º C it solidifies and it increases his volume, being able to make unusable the circuit of refrigeration.
In order to avoid these disadvantages the water with antifreeze and other additives is mixed, denominating itself to the cooling liquid mixture. This liquid presents/displays the following properties:
or the point of freezing of the water Diminishes until - 30º C, according to its concentration.
or It avoids the corrosion of the metallic parts of the circuit, due to the additives that enter their composition.
Thus, then, the cooling liquid will be left made up of:
or distilled Water.
or Antifreeze (etilenglicol).
or Borax (2 to 3%): inhibitor of the corrosion and the oxidation.
or Antiespumante.
or Colorante.
Maintenance
This maintenance will consist of the following points:
or periodic Verification of the level of the cooling liquid in the expansion glass. The liquid level has to be included/understood between the marks maximum and minimum that appear in the expansion glass. It is not had to fill never the glass completely, is due to leave a free space for the steam.
or periodic Cleaning of the circuit, according to the instructions of the manufacturer.
or Verification of flights and substitution of the deteriorated flexible sleeves.
or Maintenance of the good general state and tension of the strap of the pump. It agrees to take to a strap of spare part and tools to mount it.
or Verification of the operation of the thermostat and the entrance in operation of the electroventilador.
or outer Cleaning of the radiator.