GB1573747A

GB1573747A - Method of and apparatus for preparation of an air-fuel mixture

Info

Publication number: GB1573747A
Application number: GB3540877A
Authority: GB
Original assignee: OS BAD ROZWOJOWY SAMOCH
Current assignee: OS BAD ROZWOJOWY SAMOCH
Priority date: 1976-08-27
Filing date: 1977-08-24
Publication date: 1980-08-28
Also published as: DE2738428A1; DE2738428C2; SU1140690A3; JPS5329413A; FR2363004B1; SE7709569L; FR2363004A1; CA1087048A; JPS6124539B2; IT1083602B

Description

(54) METHOD OF AND APPARATUS FOR PREPARATION OF AN AIR-FUEL MIXTURE (71) We, OSRODEK BADAWCZO- ROZWOJOWY Y SAMOCHODOW MAtOLITRAZOWYCH "BOSMAL" BIELSKO-BIAkA, ul. Partyzantów 44, Poland an enterprise organised and existing under the laws of Poland do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of and apparatus for preparation of an air-fuel mixture especially for use in internal combustion engines having a spark ignition.

There are many methods known and used in the art of atomization of liquid fuels by means of a high-velocity gas to feed internal combustion engines having spark ignition.

One method for fuel atomization involves the use of a venturi tube used in a carburretor, and there are known carburretors with adjustable venturi. There are also known methods which aim at improvement of fuel feed systems, these methods including atomization in a sonic Dresserator carburretor with adjustable venturi, atomization in sonic-type idle-run nozzle and other systems wherein atomization takes place in sonic nozzles.

Finally there are fuel injection systems with air delivered to the injector.

Disadvantages of methods known in the art are highly complicated equipment for atomization of fuel, complicated systems to control the ratio and the rate of air-fuel mixture, insufficient atomization of fuel and poor precision in control of the mixture in view of high requirements which modern engines have to meet as regards the cleanness and efficiency of combustion.

An object of the present invention is to obviate or mitigate the above disadvantages.

According to the present invention there is provided a method of preparing an airfuel mixture, especially for internal combustion engines having spark ignition by using for continuous control of the air fuel ratio and atomization of fuel compressed air at a pressure higher than the ambient atmospheric pressure and controlled in dependence upon the revolutions of the engine crankshaft driving an aircompression pump, upon the engine load, upon the degree of opening of the mixture throttle valve, the value of vacuum downstream of which controls the position of a delivery rate throttling valve, and upon other parameters such as the external circumstances which exert an influence upon the value of the vacuum downstream of the mixture throttle valve, in such a way as to obtain a mixture content ensuring maximum effective pressure within the full range of engine loads, giving the minimum consumption of fuel and/or giving a minimum of toxic components in exhaust gases in the range of engine partial load, the fuel being, at the same time, continuously atomized and homogenized, a mixture thus prepared being introduced to the engine intake manifold upstream of the mixture throttle valve, said mixture mixing in the said manifold with the air induced by the engine to charge the engine cylinders.

Further, according to the present invention there is provided apparatus for preparation of air-fuel mixture by use of compressed air under regulated pressure, including an atomizer installed in an intake manifold of an internal-combustion engine having spark ignition, upstream of the mixture throttle valve and being connected, through a passage to a float chamber containing fuel, and through a passage for compressed air at a pressure higher than the ambient pressure to a conditioning and control system, said atomizer being provided with a diffuser opening towards the engine intake manifold upstream of the mixture throttle valve where the mixture is mixed with the air induced by the engine to produce the charges for the engine cylinders.

The atomizer of the apparatus is preferably a multistage atomizer consisting of a series of stages of various shapes, sizes, and angles of operation and of fuel and communicating passages, said atomizer being of unit construction and of circular internal section and causing the induced fuel to be thoroughly atomized and homogenized due to various velocities and flow directions of streams of compressed air. One or more stages of the said atomizer may be connected with a passage through which exhaust gases are delivered.

The mixture throttle valve of the apparatus consists preferably of symmetrically opening elements, the shape of the said elements being suited to the shape of the cross-section of the engine intake manifold. An idle-run atomizer can be installed in this mixture throttle valve, said atomizer operating only when the throttle is closed and consisting of a Laval nozzle located in the axis of a mixture flow, a port co-axially located under the Laval nozzle being used with another suitably staged nozzle, said latter nozzle expanding the homogenized and atomized mixture downstream of the mixture throttle valve.

The float chamber of the apparatus has a conventional vent hole, said vent hole being connected to the engine intake manifold space upstream of the mixture throttle valve or preferably the said chamber being connected, through a passage, with the passage through which the compressed air is delivered to the atomizer, this arrangement securing a suitably controlled delivery of fuel irrespective of fuel induced by the atomizer jets.

The conditioning and control system of the apparatus includes a gas delivery unit, said unit preferably consisting of a displacement pump coupled with the engine crankshaft and having preferably a centrifugal governor mounted on the pump shaft, said governor controlling a release valve or a pressure reducing valve, and of a unit controlling the conditioning system. the said unit regulating the gas pressure, in accordance with engine speed and load, by means of a compensation and control reservoir with passages connecting the said reservoir with the atomizer, by means of a delivery rate throttling valve said throttling valve being pneumatically coupled with the pressure existing downstream of the engine mixture throttle valve and being mechanically linked with the accelerator pedal together with the engine mixture throttle valve.In an alternative arrangement, the conditioning system is controlled by means of the delivery rate throttling valve connected to the passage for compressed air and with the atomizer, said delivery rate throttling valve being controlled either by a pneumatic actuator responding to the pressure existing downstream of the mixture throttle valve or being mechanically controlled by the accelerator pedal together with the mixture throttle valve within the range of dynamic control of mixture ratio.In an alternative arrangement said conditioning system is controlled by an electronic control system where the basic input values for the said electronic control system are engine speed, position of the accelerator pedal and the mass of air charge induced by the engine; the auxiliary input values for the said electronic system being, for instance, temperature and humidity of induced air, and engine temperature.

Quantitative and qualitative control of air-fuel ratio, and a good atomization and homogenity of mixture is obtained so that the combustion process is complete at a considerable excess of air, and that the volumetric and thermal efficiency of cylinders is improved.

In consequence a higher economy in fuel consumption is achieved, the contents of toxic constituents in exhaust gases is reduced, and the overall performance of the engine is improved, i.e. the power and the torque of the engine. The apparatus is also relatively simple in construction and in production.

Embodiments of the present invention will now be described by way of example, with reference to the accompanying drawing, in which: Fig. 1 illustrates diagrammatically one embodiment of apparatus according to the present invention: Fig. 2 illustrates an idle-run atomizer for use in the apparatus of the present invention: Fig. 3 illustrates in longitudinal section a further embodiment of apparatus according to the present invention; Fig. 4 illustrates in longitudinal section, the apparatus of Fig. 3 with modified atomizer.

Fig. 5 is a top view of the apparatus of Fig. 4 with the delivery rate throttling valve shown in section.

Fig. 6 illustrates in section, a modified atomizer used in the apparatus of Fig. 3: and Fig. 7 illustrates, in section, the modified atomizer of Fig. 4 supplied from two sources of gas.

Referring firstly to Fig. 1, air compressed according to the revolutions of the engine shaft by a pump 14, preferably a displacement pump, controlled preliminarily by a governor 15 and a release valve 16, is supplied through a pipe 9 to a multi-stage atomizer 1. Within the pipe 9 upstream of the atomizer 1 is a throttling valve 18 controlling the rate of delivery of compressed air to the atomizer 1 and which, at starting and idle running of the engine, is in the position closing the passage through the pipe 9. The throttling valve 18 is bypassed by a duct 19 at the intake end of which is a mushroom valve 36 of which the stem 37 rests on a diaphragm 38 urged by a spring 39 to lift the mushroom valve and open the by-pass duct 19 at starting and idlerunning of the engine.When the drive opens the mixture throttle valve 5, the delivery-rate throttling valve 18 follows the opening of the mixture throttle valve 5 and also opens but to a lesser extent, said delivery-rate throttling valve 18 being controlled by an actuator which is not shown in the drawing and which responds to the negative pressure downstream of the mixture throttle valve 5. At the same time, in the compensation and control reservoir 17, compensating the pulsations of the pump and connected through a tube, not shown in the drawing, to the passage 4 downstream of the mixture throttle valve 5, the spring force is overcome both by compressed air above the diaphragm and increase of vacuum below the diaphragm and downstream of the mixture throttle valve 5, closing the mushroom valve 36 and thus allowing the throttling of the passage 9 through the throttling valve 18.

Compressed air flows to the atomizer 1 commensurate with the increased revolutions of the pump 14 and the opening of the delivery-rate throttling valve 18. This follow-up pneumatic control of the throttling valve 18 is effected up to full opening of the mixture throttle valve 5, and is an economical control ensuring complete combustion of a fuel/air mixture of optimum weakness. Moreover, further compressing of the accelerator, when the mixture throttle valve 5 is already fully opened, causes further opening of the delivery-rate throttling valve 18 up to full opening thereof, and. consequently, an appropriate enrichment of the mixture, this in effect providing a dynamic control.

In the multi-stage atomizer 1, which is of venturi shape, the compressed air undergoes considerable acceleration along the length of the first stage 30 of converging truncated conical shape and then at the throat or a second stage 31, the accelerated compressed air sucks fuel through radiallyinwardly-directed nozzles 32, from an annular duct 33 communicating with a float chamber 8 through a jet passage 7, and atomizes only that amount of fuel which is consistent with the instantaneous overpressure and speed of the compressed air.In the third stage 35 of diverging truncated conical shape of the atomizer, the mixture produced at the second stage 31 thereof accelerates and is next attacked by air streams entering the atomizer 1, substantially at right angles to the direction of flow of the mixture, through a circumferentially-spaced set of nozzles 34 which extend through the wall of the atomizer, and derived from the air stream flowing around the atomizer 1. Alternatively and preferably, the air streams entering the atomizer 1 are derived from air streams delivered to the set of nozzles 34 from passage 9 through passages (not shown in Fig. 1), in the atomizer. The mixture thus atomized and uniform flows out from the atomizer 1 through a diffuser 10 into the passage 4 from the engine intake manifold where it is mixed in a known way with the air sucked in by the engine.

At idle running, when the mixture throttle valve 5 is closed, the atomizing effect of the atomizer 1 is disturbed by the mixture throttle valve 5 and, for this reason, an idle run atomizer 12, shown in Fig. 2, has been incorporated in the mixture throttle valve 5 centrally of the throttle plate 40 and of the throttle shaft 41, and makes use of the considerable over-pressure upstream of the mixture throttle valve 5, a portion of the atomized mixture, sucked in by the engine pistons, being accelerated in a first nozzle section 42 made in the shaft 14 at the upstream side of the throttle plate 40, the remainder of the mixture finding its way to a slot 43 surrounding a second nozzle section 44 made through the plate 40 in axial alignment with the first nozzle section 42, said remainder of the mixture accelerating in the slot 43 and colliding with the mixture portion flowing through to the second nozzle section 44 from the first nozzle section 42, the re-combined portions of the mixture next accelerating further in the appropriately-profiled next and third segment 45 of the nozzle and expanding as it flows into the passage 4 from the engine intake manifold, downstream of the mixture throttle valve 5.

When braking with the engine, the mixture throttle valve 5 is closed and the engine revolutions are sufficiently high, the high vacuum downstream of the mixture throttle valve 5 closes the delivery-rate throttling valve 18, whereas the diaphragm 38 of the compensating reservoir 17 pulls the mushroom valve 36 with compressed air acting thereabove and vacuum acting therebelow, thus closing the idle run or bypass duct passage 19 and cutting off entirely the compressed air flow upstream of the atomizer 1, and, in consequence, the delivery of fuel to the carburettor.

Referring now to Figs. 3 to 7, the air compressed in conformity with the engine shaft revolutions by the pump 14 and controlled preliminarily by the governor 15 and the release valve 16, is delivered to a delivery-rate throttling valve 20, which is controlled by an actuator 21 (Fig. 5) responsive to the value of pressure downstream of the mixture throttle valve 6, the throttling valve 20 controlling the pressure of compressed air delivered to the atomizer 2 (Figs. 3 and 6) or 3 (Figs. 4 and 7) through the pipe 9 and to the float chamber 8 through a passage 13, depending upon the value of vacuum downstream of the mixture throttle valve 6, either at the driver's will or depending upon engine load and engine working conditions.The operation of the delivery-rate throttling valve 20 is such that it is fully closed at the value of vacuum existing when braking with the engine, thus cutting off completely the outflow of fuel, whereas at the value of vacuum existing on idle running of the engine, the slot through the valve 20 is partially opened, and the atomizer 2 (Fig. 6) and the idle-run atomizer 12 (Fig. 2) operate with the projections at the adjacent edges of the shutters of the mixture throttle valve 6 in contact with one another.Beginning from partial opening and up to full opening the mixture throttle valve 6, the delivery-rate throttling valve 20 is controlled by the actuator 21, next when the mixture throttle valve 6 is already fully open the enrichment of the mixture being dynamically controlled, by further mechanical opening of the delivery-ratethrottling valve 20, through further pressure on the accelerator pedal. An example of the design of the actuator 21 is shown in Fig. 5.

The multi-stage atomizer 2 of venturi shape (Figs. 3 and 6) operates in such a way that compressed air delivered thereto through the pipe 9 at an appropriate pressure, corresponding to the existing stage of engine operation and external conditions, undergoes considerable acceleration along the length of the first stage 50 of converging truncated conical shape, flows through the throat or second stage 51 and into the third stage 52 of divergent frustoconical shape.

The compressed air delivered through the pipe 9 into ducts 53 extending through the wall of the atomizer 2 from the upstream end of the latter and opening into the third stage 52 with convergence towards the axis of the atomizer 2 in the direction of flow of the air, sucks in through passages 54, fuel delivered from the float chamber 8 through the passage 7, the sucked-in fuel being delivered with the same overpressure of an appropriate value and at the same time being atomized, accelerated in the ducts 53 and colliding at substantially right angles with the expanding stream of compressed air in the third stage 52 of the atomizer 2, where further atomization of the fuel drops in the mixture as well as further mixing of the said mixture and its homogenization take place; thereafter, the stream of the mixture moving with considerable velocity is attacked by successive streams directed through passages 55 from an annular duct 56 defined by the seat for the atomizer 2 at the downstream end of the latter and an annular channel 57 (Fig. 7) in a flat surface area 58 about the downstream end of the third stage 52 at the downstream end of the wall of the atomizer 2, longitudinal ducts 59 extending through the wall of the atomizer 2 axially parallel with the latter from the upstream end of the atomizer into the annular channel 57 whereby the annular duct 56 is supplied with compressed air delivered through the pipe 9.The mixture, having been atomized and homogenized several times, flows out through the diffuser 10 and mixes in a known way with the air stream flowing through the passage 4 about the housing for the atomizer 2, the air being sucked in almost without hindrance by the engine.

In the embodiment shown in Fig. 4, the apparatus includes an atomizer 3 as well as an additional passage 11 delivering another gas with different parameters to the atomizer 3. The apparatus of Fig. 4 is similar in many respects to and operates in a manner similar to the apparatus of Fig. 3, and, where appropriate, the same reference numerals have been applied. However, the atomizer 3 (Fig. 7) used in the Fig. 4 apparatus, differs from the atomizer 2 (Fig.

6) used in the Fig. 3 apparatus, to adapt same for exploitation in some stages of the other gas delivered thereto through the passage 11. The other gas may be, for example, exhaust gases from the engine exhaust system, which has different parameters than the gas supplied through the passage 9.

The atomizer 3 has a cylindrical intake passage 60 of the same diameter as the upstream end of the first stage 50 and through which the compressed air delivered through the pipe 9 passes into in the first stage 50, undergoes considerable acceleration, flows through the throat or second stage 51 and into the third stage of divergent frusto-conical shape. The wall of the passage 60 is fashioned to provide therearound an annular duct 61 into which the passage 11 opens. The ducts 53 extending through the wall of the atomizer 3 open from the annular duct 61 and discharge as before into the third stage 52 with convergence towards the axis of the atomizer in the direction of flow of the air through the atomizer.The ducts 59 extending through the wall of the atomizer 3 into the annular channel 57 in this instance also open from the annular duct 61, or, alternatively, as shown in dotted lines in Fig.

7, open from the upstream end of the first stage 50 of the atomizer 3.

In an alternative version of the apparatus the pressure of gas delivered to the atomizer is controlled by means of an electronic system directly controlling the pressure and the delivery rate of the pump or the operation of the pressure reducing valve in accordance with an output signal determined by parameters such as the engine speed, the position of accelerator pedal, the mass of charge induced by the engine, the temperature and the humidity of air induced by the engine, and the engine temperature.

WHAT WE CLAIM IS: 1. A method of preparing an air-fuel mixture, especially for internal combustion engines having spark ignition, by using for continuous control of the air fuel ratio and atomization of fuel compressed air at a pressure higher than the ambient atmospheric pressure and controlled in dependence upon the revolutions of the engine crankshaft driving an aircompression pump, upon the engine load, upon the degree of opening of the mixture throttle valve, the value of vacuum downstream of which controls the position of a delivery rate throttling valve, and upon other parameters such as the external circumstances which exert an influence upon the value of the vacuum downstream of the mixture throttle valve, in such a way as to obtain a mixture content ensuring maximum effective pressure within the full range of engine loads and giving the minimum consumption of fuel and/or giving a minimum of toxic components in exhaust gases in the range of engine partial load, the fuel being, at the same time, continuously atomized and homogenized, a mixture thus prepared being introduced to the engine intake manifold upstream of the throttle, said mixture mixing in the said manifold with the air induced by the engine to charge the engine cylinders.

2. A method as claimed in Claim 1 comprising supplementing the compressed air by another gas having different parameters than compressed air, such as the exhaust gas of the engine.

3. A method as claimed in claim 1 wherein the compressed air forms up to 30% of the charge induced by the engine.

4. A method as claimed in any one of the preceding claims wherein, when braking with the engine, there is utilized the vacuum downstream of the closed mixture throttle valve produced by high engine revolutions in order to cut off the flow of compressed air to the atomizer and thus cut off the delivery of fuel.

5. A method as claimed in any one of the preceding Claims, wherein during idling of the engine, when the mixture throttle valve is closed and when the demand of fuel is small and the quality of atomization is poor, a high difference of pressures existing upstream and downstream of the mixture throttle valve is utilized to homogenize further the air-fuel mixture by causing the previously separated high velocity streams of mixture to collide and expand.

6. A method as claimed in any one of the preceding Claims, wherein a mixture throttle valve is used with symmetrically opening elements, this symmetrical arrangement of throttle elements enabling an almost axial flow of mixture.

7. A method as claimed in any one of the preceding Claims, wherein the fuel is not only continuously induced but is also delivered by means of the compressed air, under controlled pressure to the nozzles of a multi-stage atomizer, the positions and the cross-sectional areas of the individual nozzles being constant and not susceptible to maladjustment, and the fuel being atomized several times by the streams of the gas under a controlled pressure outflowing from the nozzles of the individual stages.

8. A method as claimed in Claim 7, wherein the atomizer has certain stages in which the compressed air under controlled pressure is used for fuel atomization and other stages in which exhaust gases are used, said compressed air pressure being controlled by means of the delivery rate throttling valve, said delivery rate throttling valve being controlled by a pneumatic actuator, the operation of the said actuator being governed by the pressure existing downstream of the mixture throttle valve said compressed air pressure being also mechanically controlled by the accelerator pedal linked to the mixture throttle valve.

9. A method as claimed in Claim 7 or 8, wherein the pressure of the compressed air and the rate of delivery thereof upstream of the atomizer are controlled by an electronic translation of input data such as engine speed, position of accelerator pedal, mass of the charge induced by the engine, and of additional data such as the temperature and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. divergent frusto-conical shape. The wall of the passage 60 is fashioned to provide therearound an annular duct 61 into which the passage 11 opens. The ducts 53 extending through the wall of the atomizer 3 open from the annular duct 61 and discharge as before into the third stage 52 with convergence towards the axis of the atomizer in the direction of flow of the air through the atomizer. The ducts 59 extending through the wall of the atomizer 3 into the annular channel 57 in this instance also open from the annular duct 61, or, alternatively, as shown in dotted lines in Fig. 7, open from the upstream end of the first stage 50 of the atomizer 3. In an alternative version of the apparatus the pressure of gas delivered to the atomizer is controlled by means of an electronic system directly controlling the pressure and the delivery rate of the pump or the operation of the pressure reducing valve in accordance with an output signal determined by parameters such as the engine speed, the position of accelerator pedal, the mass of charge induced by the engine, the temperature and the humidity of air induced by the engine, and the engine temperature. WHAT WE CLAIM IS:

1. A method of preparing an air-fuel mixture, especially for internal combustion engines having spark ignition, by using for continuous control of the air fuel ratio and atomization of fuel compressed air at a pressure higher than the ambient atmospheric pressure and controlled in dependence upon the revolutions of the engine crankshaft driving an aircompression pump, upon the engine load, upon the degree of opening of the mixture throttle valve, the value of vacuum downstream of which controls the position of a delivery rate throttling valve, and upon other parameters such as the external circumstances which exert an influence upon the value of the vacuum downstream of the mixture throttle valve, in such a way as to obtain a mixture content ensuring maximum effective pressure within the full range of engine loads and giving the minimum consumption of fuel and/or giving a minimum of toxic components in exhaust gases in the range of engine partial load, the fuel being, at the same time, continuously atomized and homogenized, a mixture thus prepared being introduced to the engine intake manifold upstream of the throttle, said mixture mixing in the said manifold with the air induced by the engine to charge the engine cylinders.

humidity of air induced by the engine, and engine temperature, into an output signal, said output signal suitably controlling the operation of a pump or of a pressure reducing valve.

10. Apparatus for preparation of an airfuel mixture by use of compressed air under regulated pressure, including an atomizer installed in an intake manifold of an internal-combustion engine having spark ignition, upstream of a mixture throttle valve and being connected, through a passage to a float chamber containing fuel, and through a passage for compressed air at a pressure higher than the ambient pressure to a conditioning and control system, said atomizer being provided with a diffuser opening towards the engine intake manifold upstream of the mixture throttle valve where the mixture is mixed with the air induced by the engine to produce the charges for the engine cylinders.

11. Apparatus as claimed in Claim 10 wherein said atomizer is a multi-stage atomizer consisting of a series of stages of various shapes, sizes, and angles of operation and of fuel and communicating passages, said atomizer being of unit construction and of circular internal section.

12. Apparatus as claimed in either Claim 10 or 11, wherein said conditioning and control system includes a pump coupled to the engine crankshaft, said pump having a governor and a release valve to control the pressure of the air and said system further including a compensation and control reservoir connected to the pump and the governor, a passage with a delivery rate throttle valve installed therein, said delivery rate throttle valve being pneumatically coupled to the pressure existing downstream of the mixture throttle valve and being mechanically linked to the accelerator pedal together with the mixture throttle valve and a passage by-passing said delivery rate throttle valve at engine idling.

13. Apparatus as claimed in any one of Claims 10 to 12, wherein said pump is a displacement pump and said governor is a centrifugal governor.

14. Apparatus as claimed in any one of Claims 10 to 13, wherein the mixture throttle valve is equipped with an atomizer for engine idling, said atomizer consisting of a Laval nozzle situated co-axially with the stream of flowing mixture, a port co-axially situated under the said Laval nozzle, and in co-axial continuation of the latter, another nozzle for expanding the mixture and staged according to the total cross-sections.

15. Apparatus as claimed in any one of Claims 10 to 14, wherein the mixture throttle valve consisting of symmetrically opening elements, the shape of the said elements being suited to the shape of crosssection of intake manifold of the engine.

16. Apparatus as claimed in any one of Claims 10 to 15, wherein said atomizer is in the form of a combined mechanical element whose flow parameters are constant, the fuel being not only induced to the said atomizer but also delivered by the compressed air, under the regulated pressure from the float chamber, said float chamber being connected through a passage to the passage for the compressed air, certain stages of the said atomizer being connected to said passage for the compressed air, other stages being connected to a passage through which exhaust gases are delivered, the control system controlling the pressure in the passage for the compressed air including a delivery rate throttling valve, said valve being mechanically linked to a pneumatic actuator controlled by the pressure existing downstream of the mixture throttle valve and being also linked to the accelerator pedal together with the mixture throttle valve.

17. Apparatus as claimed in any one of Claims 12 to 16, wherein the conditioning and control system is in the form of an electronic system consisting of relays operable in response to parameters such as engine speed, position of accelerator pedal, the mass of the charge induced by the engine, and of relays operable in response to additional parameters such as the temperature and humidity of air induced by the engine, and engine temperature, said electronic system including a unit for translating the received data into an output signal to control the operation of the pump or of a pressure reducing valve and to regulate suitably the pressure and the delivery rate of compressed air in the passage for the compressed air.

18. A method of preparing an air-fuel mixture, substantially as hereinbefore described with reference to the accompanying drawings.

19. Apparatus for preparation of an airfuel mixture, substantially as hereinbefore described with reference to the accompanying drawings.