Cars and Tuning

The motor of four times is a motor that transforms the chemical energy of a fuel into calorific energy, that provides the mechanical energy as well necessary to move vehículo….
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The motor of four times
Introduction
The motor of four times is a motor that transforms the chemical energy of a fuel into calorific energy, that provides the mechanical energy as well necessary to move the vehicle. This transformation is properly made in the interior of the cylinder, burning the fuel dosed and prepared. These motors receive the name of combustion motors.
In order to obtain this transformation of the energy, four operations different and from stepped form are due to make.
Each one of these operations is made in a race of the piston (displacement from the P.M.S. to the P.M.I) call time and as the necessary ones are four times to make the complete cycle, the crank will give two complete returns, because it téngase in account that each race corresponds to average return in the crank (180º of turn).
Theoretical cycle - motor of explosion
In order to study the theoretical cycle, we will make it taking care of the following points:
or Displacement or route of the piston.
or Position of the valves.
or Purpose of the time.
or Openings and closings of the valves that are made in the deadlocks of this cycle.
The theoretical cycle is made in four times: admission, compression, explosion and escape.
First time: admission
The piston descends from the P.M.S. to the P.M.I. The admission valve stays open and the one of closed escape.
An emptiness or aspiration, that is believed in the cylinder it allows that it fills of mixture of air and gasoline in gas form.

Second time: compression
The piston ascends of the P.M.I. to the P.M.S. the two valves are closed.
The gases are compressed until leaving reduced to their volume to the one of the compression chamber, acquiring a pressure and an ideal temperature to produce the explosion.

Third time: explosion
A spark in the spark plug jumps, become inflamed gases and appears a considerable increase of pressure, receiving the piston a concerted effort that makes him descend energetically from the P.M.S. to the P.M.I.
The valves, during this time, have stayed closed.
To this time motor time or of work is called to him, because in him the force is obtained that really will move to the vehicle.
At the moment for burning itself, the pressure of the 45 gases reaches and surpasses Kg/cm2. The temperature of these gases can surpass 950º C.

Fourth time: escape
The piston ascends from the P.M.I. to the P.M.S.
The escape valve is opened and the admission stays closed.
During this time the expulsion of gases burned in the explosion takes place, leaving frees the cylinder for the admission of a new amount of mixture.

Practical cycle
The cycle of four times described previously, called theoretical, actually is not made exactly since it has been indicated, as far as the moments of opening and closes of the valves, existing in the reality a phase angle with respect to the moments at which the piston reaches the deadlocks. With this phase angle a better filling of the cylinder and better drained of the burned gases is obtained not only, but that improve the power and the engine efficiency.
The cycle of the motor of four times, in which the opening and closes of the valves does not agree with the deadlocks of the piston, denominates “Ciclo Práctico” or regulated.
We are going to see in what moment they are opened and they closed, in the practical cycle, the valves of admission and escapes in relation to the moment at which the piston is in its deadlocks.
Valve of admission

In the theoretical cycle it was opened at the moment at which the piston initiated, during the first time, his reduction from the P.M.S. to the P.M.I.
In the practitioner, it does a little while before reaching the P.M.S; it exists because an advance of opening to the admission (A.A.A) to take advantage of inertia which they have gases in the induction manifold and that is inhaled in the next cylinder and than they will be sent towards the interested cylinder.
As far as his closing, it happens the opposite; it is delayed. The closing takes place when the piston already has initiated the compression (second time); passed the P.M.I. a delay to the closing of the admission exists (R.C.A). With it one is able to increase to the filling, taking advantage of inertia gases.
Valve of escape

The phase angles of their opening and close, with respect to the deadlocks of the piston, are approximately equal that in the admission valves.
The opening of the escape valve takes place a little while before reaching the piston the P.M.I. after the explosion, (third time); reason why an advance to its opening exists (A.A.E). One is able to more quickly obtain outer and inner the balance between pressures of the cylinder.
It avoids the back pressures in the ascent of the piston.
The closing takes place a little while after passing the piston through the P.M.S, already initiated the admission (first time) of the following cycle. It exists because a delay in his closing (R.C.E). One is able to eliminate burned gases completely, taking advantage of also inertia gases in his exit.
ruce of valves or I overlap

As the admission valve is opened before and the one of escape it is closed after the P.M.S. due to the A.A.A and to the R.C.E, is that both valves are open simultaneously during a certain time or turn crank, called VALVE OVERLAP Or I OVERLAP.
The gases burned to their exit by the conduit of escape and due to the inertia that take, help to enter fresh gases and they will not be mixed because the densities of fresh gases and the one of burned gases are different.
A revolutionized motor will have more angle of I overlap that revolutionized other less.
Moment of inflammation of the mixture (A.E)
Also an advance to the ignition (A.E) or the injection in the diesel engine exists. This level of advance to the ignition, indicates the degrees that it needs to the steering wheel in their turn, so that the piston arrives at the P.M.S and jumps the spark in the spark plug considering the burn time. The combustion is made of a progressive form, since the mixture burns by layers in the explosion motors and on the other hand, exists a retardation to the ignition of the combustion in the diesel engines. The value of this angle, will depend on the revolutions of each motor and at every moment. These angles of setting are fixed by the manufacturer to obtain the maximum yield.
These phase angles in the opening and close of the admission valves and escape, in relation to the deadlocks of the piston, are known with the name “Cotas of Reglaje”, that they are fixed by the manufacturers for each type of motor.
In, the diagram of distribution with setting levels imagines.

Motor of two times
In the motors of two times, the complete cycle is made in two races of the piston, corresponding to a return of the crank.
The motor has lights generally, although it can have valves.
These motors lack distribution system.
The lubrication is made by mixture of gasoline and oil in the proportion of a five percent, approximately.
The refrigeration is by air mainly in the motors of small piston displacement, although also it it can be by liquid.
The main disadvantages of these motors are:
or Less thermal efficiency. Less power in piston displacement equality.
or Lubrication and irregular refrigeration.
or More noises.
or More possibility of gripaje.
or Greater specific consumption.
or Easy fine coal creation.

Rotary engine Wankel
At the present time all the rotary engines that are used in the automobiles are of the Wankel type, name of their German inventor.
The great advantage that has the rotary engine is that their pieces do not have alternative movements, but that turn. It has less movable weight, less pieces and is more compact.
It does not take distribution system, the gas admission and escape it is obtained covering and opening lights.

The refrigeration system is by liquid, activated by a pump. The lubrication system is by mixture, like the motor of two times.