CA1038452A - Method and apparatus for determining the timing angle in internal combustion engines - Google Patents

Abstract

A B S T R A C T

This application discloses a method and apparatus for measuring and/or adjusting the average timing angle over all the cylinders of an internal combustion engine with reference to a single predetermined top dead centre position. The method of measuring the timing angle comprises the steps of running the engine and producing voltage pulsations of uniform time frequency against which are simultaneously taken measurements of two values;
first, the measurements of engine speed by counting the number of pulsations for one full and precise revolution of the engine from top dead centre to top dead centre of one selected cylinder, and simultaneously counting the number of pulsations from the moment the spark plug of the selected cylinder fires to the top dead centre (for advanced firing), or from the top dead centre to the moment of firing of the spark plug (for retarded firing).
Counting two of such values enables the testing personnel to express the timing angle in degrees and to have the RPM of the engine at the time of testing, neither of which would be avail-able if only one of such two values was measured. The disclosed test apparatus also provides a mechanism responsive to such measurements, which mechanism gives a readout of the revealed timing angle and compares it with the set range of timing angles, and a servo-mechanism which automatically adjusts the obtained timing angle to the desired value within such set angle.

Description

The invention disclosed herein relates to internal -combustion engines, such as autom~bile engines, and more ~-particularly to an improved method and apparatus for measuring ~; -and/or adjusting the timing angle of the engine, i.e. the i angle of occurrence of igniting spark in the cylinder of r the engine with respect to the top dead center position of - -the pistons of the respective cylinders. In one of its ~pects, the invention relates to providing an improved ~utomatic testing syste~, such as a conveyor serving a plurality 10 Of test stands, with each of said stands adapted to receive a ; test engine and to operate such engine in a manner to ~` reveal the time of occurrence of the ignition spark with respect ' ......
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to the top dead center position of the engine piston, and to set or adjust such time, usually referred to as "timing angle", at a predetermined or desired point.
A patent application of Richard L. Smith and Dennis F. Sauerbrey, now U.S. Patent No. 3,697,865, discloses a method and apparatus for adjusting the timing angle with the use of encoder producing fast pulsations, such as 3600 pulsations per one revolution of the engine, or 10 pulsations per degree. The basis of that system is counting, in effect, 10 degrees. By such count, this system gives timing angle and -~
brings the desired result.
Such system produces good results and is particularly adaptable to certain conditions. ~owever, it cannot be economically used under all conditions. Enroder is a rather expensive device and, in addition, it is very fragile. It is very sensitive to shocks and can become unusable after rsceiving relati~ely mild shocks. Furthermore, the encoder has to be connected to the engine in a test system. It ca~not be easily connected to the engine of a vehicle in such condition as in the parking lot.
ane of the objects of the present invention is to devise a method and apparatus for measuring and/or adjustins the timing angle of the engine without requiring tne use of an encoder.
Another object of the present invention is to provide an improved test system to measure the timing angle of an inter-nal combustion engine irrespective of whether or not the engine is in a test stand or is operating in a motor vehicle or is installed for test in any other suitable condition.

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Another object of the present invention is to provide an improved engine testing system to have the engine reveal its timing angle, which system can be conveniently used in repair garages with the limitations of equipment and personnel present in such garages.
Another object of the invention is to provide an improved test stand adapted to receive and to operate a test engine to reveal its timing angle, but without producing actual ignition in the cylinders thereof, thus eliminating ~e necessity of operating the engine on gasoline or on any inflam-mable gas, such as butane gas, as well as eliminating the inconveniences and complications connected therewith.
Another object of the invention is to provide an improved testing system for automobile engines, said system including a plurality of test stands receiving test engines from loading stations to have each engine securely installed in a respective stand for the tes~, to run the ensine in a manner to reveal correctly its timing angle, to adjust the distributor automatically to produce a desired timing angle, to remove the test engine from the respective test stand, and to deliver the tested engine to the unloading station.
A further object of the invention is to provide an improved engine test stand adapted to receive and to run the test engine to reveal its timing angle, all without requiring cooling the engine with water or removing exhaust gases.

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, A still further object of the invention is to provide an improved engine testing system adapted to run the engine to reveal its timing angle, to release its distributor fixing means, such as distributor hold down bolt, to adjust the distributor to produce a predetermined timing angle, and thereupon to retighten said fixing means.
A still further object of the present invention is to provide an improved engine testing system of the foregoing character, and including a spark plug operated by the ignition system of the engine, as related to à selected cylinder, means to produce pulsations of unifrom time frequency, means to count simultaneously the number of pulsations so produced for one complete revolution of the engine and, therefore, also for one degree of engine rotation, and at the same time count the number of such uniform pulsations that take place from the moment ~he spark plug sf the selected cylinder fires until the moment the piston of the selected cylinder reaches the top dead center. The timing angle is then obtained by dividing the time of the last value by the time for one degree of engine rotation.
It is a further object of the invention to provide an improved timing angle measuring and/or adjusting system in which the uniform pulsations are produced by a crystal oscilla-tor of ~nown and uniform time frequency.
It is a further object of the invention to provide an i~proved timing angle measuring and/or adjusting system in which the signal is received from a magnetic pickup activated by the harmonic damper and is gi~en at the beginning and at the end of one revolution of the engine at top dead center.

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A still further object of the present invention is to provide a second signal at the mo~ent the spark plug of the selected cylinder fires.
A still further object of the present invention is to pags the two signals through a signal conditioner which converts each of the signals into a low voltage pulse compatible with the system.
A still further object of the present invention is to provide an improved method and apparatus for measuring and/or ~10 adjusting timing angle of internal combustion engines, in which method and apparatus there is taken simultaneously a count of two values with respect to the same uniform time pulsations.
First, the count of pulsations per one full and precise revolution of the engine, which gives also the number of pulsa-tions per one degree of engine rotation; and, second, the number of pulsations from the moment the spark plug in the selected cylinder fires to the moment when the piston in the 3elected cylinder reaches the top dead center (for advanced firing). It can be understood that having received the values for both of these counts, the timing angle may be easily computed. On the other hand, if only one system of value is counted, the timing angle is not obtainable since if number of pulsations in the timing angle is obtained, there is no way of expressing it with relation to the degrees of rotation ;
of the engine since the value of the pulsations in the timing angle not being expressed with relation to rotation of the engine is meaningless.
A still further object of the present invention is to provide an improved method and apparatus for measuring and adjusting the timing angle of an internal com~ustion engine which also gives the values for RPM of the engine during the ~, time the mea~urements are taken.
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A still further object of the present invention is to produce an improvea method and apparatus for measuring and/or adjusting the timing angle of internal combustion engines, which timing angle measurement can be used to adjust the distributor and to compare the obtained results with the high and ~he low limits of the established range of such angle.
A still further object of the invention is to provide an improved method and apparatus for measuring and/or adjusting the timing angle of the engine, in which there is provided a servo-mechanism to adjust the distributor.
A still further object of the present invention is to provide an improved method and apparatus for measuring and/or adjusting the timing angle of internal combusti~n engines wherein the necessary mathematical calculations are performed with the use of binary mathematics.
A further object of the present invention is to pro-vide an improved method and apparatus for measuring and/or adjusting the true average timing angle-of an internal combustion engine.
Another object of the present invention is to provide an improved method and apparatus for measuring and/or adjusting both, the timing angle of one selected cylinder in an internal combustion engine, or the true average timing angle over all the cylinders of an internal combustion engine.
It is an added object of the present invention to provide an improved test system of the above nature which is relatively si~ple in construction, dependable in operation, is operated with the minimum of personnel, and is relatively easy to repair and service.

Further objects and advantages of this invention will ~ -be apparent from the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification, wherein like reference characters designate corresponding parts in the several views.
Figure 1 is a perspective view of the control box for operating the system of the present invention.
Figure 2 is a side view of the construction of Figure ~ -1 with one side panel removed.
Figure 3 is a plan view of the system as it may be used i~ a plurality of test stands connected by a conveyor for measuring and/or adjusting the timing angle of internal com-bustion engines in quantity production.
Figure 4 is a side view of one test stand with the engine shown in said stand.
Figure 5 is a diagram showing one system as it may be used onan engine outside a test stand.
Figure 6 is a diagram showing one system with a multiplying counter, binary timing counter and timing binary coded decimal counter.
Figure 7 is a diagram showing a complete system with the multiplying counter, timing binary counter, timing binary o~ded decimal counter, RPM binary counter, and a RPM binary coded decimal counter.

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Figure 8 is a diagrammatic view of ~le complete system, including the apparatus necessary to compute the timing angle and RPM of the engine, to compare the timing angle obtained with a predetermined range of timing angles, for the predetermined range of RP~ and automatically adjust the distributor to produce a desired value of timing angle, and further including means to internally test the system to insure its correct operation.
Figure 9 is a modification of means for producing the top dead center signal by u~ing a slot in the harmonic damper.
Figure 10 is still another modification of means for producing a top dead center signal by using a hole in the harmonic damper.
Figure 11 shows another method of picking up a signal when the spark plug fires by a non-inductive means.
Figure 12 shows a method of picking up said spark signal without the use of a spark plug.
Figure 13 shows an inductive method of picking up a spark signal.
Figure 14 shows a method whereby the spark signal can bè picked up from the distributor of the internal combustion engine.
Figure 15 is a diagram showing one system as it may be used on an engine outside a test stand to determine eitner the timing angle of one selected cylinder or the true average timing angle over all the cylinders of said engine.

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Figure 16 is a graph illustrating the operation of the present invention in calculating the true average timing angle of an internal combustion engine running in the advanced ignition condition.
Figure 17 is a grapA illustrating the operation of the present invention in calculating the true average timing angle of an internal combustion engine running in the retarded ignition condition.
Figure 18 is a diagrammatic illustration of a complete .
system set up to find the true average timing angle over all the cylinders of an internal combustion engine regardless of whether it is running in the advanced or retarded spark con- .
dition.
Figure 19 is a diagrammatic illustration of a complete system set up to ~ind either the true spark advance of one selected cylinder or the true average tim ng angle o~re- 211 the cylinders in an internal combustion engine and including the apparatus necessary to compute the timing angle and RPM . :
of the engine, to compare the timing angle obtained with a predetermined range oftiming angles, for the predetermined range of RPM, and automatically adjust the distributor to ~ -produce a desired value of timing angle, and further including~
means to internally test the system to insure its correct op~ration. ' '' Figure 20 is an illustration of how the system shown in Figure 19 may be used with an engine having a solid state ignition system.
It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and :~
of being practiced or carried out in various ways within .... -- 10 --. . , . ~.
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the ~cope of the cIaims. Also, it is to be understood that he phraseology and terminology employed herein is for the purpose of description and not of limitation.
Canadian Patent No. 908,746 dated August 29, 1972 Richard L. Smith and Dennis F. Sauerbrey discloses a method and apparatus of measuring and adjusting the timing angle of an internal combustion engine by measuring, in effect, the degrees of the angle through which the spark is advanced. with the use of such a method and apparatus, only one set of values is being measured and after the answer in terms of such a value, namely the size of the timing angle, is received, the process is, in effect, completed.
In accordance with my invention, I measure simultan-eously two values. First, I measure the time for one full and precise revolution of the engine from top aead center of the selected cylinder to the top dead center thereof. I make such measurements again~t uni~orm pulsations produced with the device capable of producing pulsations of sufficient frequency, which frequency must be uniform. While such pulsations are produced, I also measure the nu~ber of pulsations occurring from the moment the spark in the selected cylinder fires to the moment the piston in the selected cylinder of the engine reaches the top dead center (for advanced timing). Measuring both values at the same time, I receive values which enable me to-compute the timing angle of the engine.
It can be easily understood that if I would count only one value, such as the pulsations from the moment the spark plug of the selected cylinder fires to the moment the piston in the selected cylinder reacnes top dead center, I would .. . .

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receive only the time which elapsecl between these two moments but would have no way of expressing this time in terms of the angle, that is timing angle, since in order to do that I
would need to know the time the engine takes to rotate through one degree. Since I count at the same time the number of pul~ations through one full and exact revolution, I can compute the number of pulsations per one degree by dividing the number of pulsations for one revolution by 360. Thereupon, I divide the number of pulsations which occurred between the moment of the spark plug firing to the moment the piston in the selected cylinder reaches the top dead center position by the number of pulsations for one degree. In such a manner I obtain the timing angle expressed in degrees.
Sinc~ we are concerned primarily with automobile engines which operate on the principle of four-stroke cycle, the engine makes two full revolutions during which the spark plug fires once. Therefore, I prefer to count the number of pulsations for two full and exact revolutions.
The above-described method of simultaneously counting two values, namely first the number of pulsations with respect to revolutions of the engine and thereupon number of pulsations which take place while the engine rotates through the timing angle, I obtain a definite answer which could not be received -counting only one value.
Any device producing known and uniform pulsations can be used for the purposes of the present invention. Since counting of pulsations is done siml~ltaneously, only one device producing ~ulsations may be used, and both values be counted against pulsations produced by such device.

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For the purposes of producing pulsations, I prefer to use a crystal oscillator since such a device can be selected to produce known and uniform pulsations of exc~edingly high frequency, such as two million pulsations per second.
In order to define the limits of one revolution or two revolutions, I use indications of top dead center, whicn indications can be produced with magnetic pickup cooperating with such a device as harmonic damper provided on the engine.
Spark plug firing in one selected cylinder is used, and such spark plug may be either wi~n the cylinder or outside The indication of the piston in the same selected cylinder reaching the top dead center may be the same as that used to desiynate the limit of the revolutions.
In the drawings, there is shown an er~odi~ent of the invention operating in a manner as required for measuring and/or revealing the timing angle of one or more automobile ensines in production testing of sudl engines.
I adapt my system to production requirements in an automobile plant. The engine may be tested in any suitable condition it is found in production without any special stands or conveyors, or the test may be made in one stand, or in a large number of stands connected by a conveyor into one system adapted to receive the engines from loading stations and to distribute them to unoccupied stands of the conveyor for test, and after the test to receive them from the test stands and direct them to an unloading station.

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103~52 It 5hould be understood that it is possible to produce and use a signal other than that of true top dead center as long as the exact relationship between ~le sisnal and true top dead center is known so tnat the resulting answer may be corrected by this difference. Similarly, it is possible to use a signal o~ler than the number one spar~ plug as long as the exact relationship between the signal and t~e firing of the number one spark plug is known so that the resulting answer may be corrected by tihis difference. For example, the number two spark plug could be used.
It hould be further understood that it is possible to produce and use a signal other than from a pre-selected spark plug, such as from the coil, or the impulses generated by the distributor.
Referring specifically to Figure 3, the same shows a test installation including a plurality of test stands 10 interconnected with the aid of a conveyor 11, which may be such a~ those disclosed in the co-pending applications of V.G.
Converse III, et al, Serial No. 707,033, filed on February 21, 1968 for Accumulator Conveyor System, now patent No. 3,631,967, and Serial No. 717,103, filed on March 29, 1968 for Automated Engine Test Conveyor, now patent No. 3,527,087. The conveyor 11 ~s adapted to serve such stands 10 by delivering the test engines, such as 12, (see E'igure 4) from the loading station 13 to the respective stands. The test stand which is empty would ~
receive for test the first passing untested engine, and upon -completion of the test return the tested engine to the conveyor for delivery to the station 13 for unloading. The tested ~ -engine would not be received by any other stands, even if the stand is empty.

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The test performed in each stand depends on the requirements set the~efor, and the engines may be run on gasoline, butane gas, or may be operated by compressed air or by an electric or fluid (gas or liquid) motor. Use of compressed air or an electric or fluid motor insures maintenance of a predetermined speed and does not re~uire cooling of the engine, although water may be used in the engine to perform leak tests such as to determine leakage from water cavity to at~osphere. Oil pressure can also be conveniently checked in this test by being continuously monitored while the engine i8 running, with a view of stopping the engine snould oil pressure fail. A visual and audible check for noise can also be done.
Figure 4 illustrates one test stand showing a test engine 12 received by the stand and operatively po~tioned therein to be driven with the aid of a motor 14 connected to the engine 12 by the coupling 16. The control box 17 is pro-vided in the stand 10 for the purposes explained below.
Now turning to the computation of the timing angle, this is accomplished by measuring the time in seconds between the moment of firing of the number one spark plug (assuming advanced timing) and the moment the piston of the selected cylinder reaches top dead center, and dividing this number by the time in seconds per one degree of engine revolution.
Thi~ can be represented ~y the mathematical formula :
Timing Angle = 720 -, where Y equals time in seconds between 3park plug firing and top dead center and X e~uals the time in seconds for two revolutions of the engine.

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In order to be able to get values for Y and X, two 3ignals from the engine are needed, the top dead center , . , (TDC) signal and the spark firing signal.
Referring to Rigure 4, the TDC (top dead center) signal is produced as follows : On the front end of the engine 12 there is operatively mounted a harmonic damper 15 provided on its periphery witll a slot or notch 18 related to the top dead center position of the piston of number one cylinder.
A magnetic pickup 2~ is operatively installed in the stand in such a manner that when the piston of number one cylinder is at its top dead center position, the notch 18 cooperates with said magnetic pickup 20 in such a manner that an electrical impulse is produced each time the number one cylinder is at its top dead center position. This is the TDC signal, the use of which will be explained below.
Referring to Figure 5, the distributor 38 supplies high voltage through the spark plug wire 26 to fire the spark -plug 31. me spark firing signal is produced by a wire loop, coil, or clip 32 surrounding the spark plug wire 26, a current being induced in said wire loop, coil, or clip 32 each time the high voltage passes through the spark plug wire 26. This ~;
induced current is ~he spark ~irin~ signal whose purpose will be explained in detail below. It should be understood that ~n accordance with the invention, the spark plug 31 does not need to be mounted in the engine 12 but can be mounted extern-ally thereto, or the spark fixing signal may be produced without the use of any spark plug.
~' ~03~452 Referring to Figures 6, 7 and 8, the TDC signal obtained in the above manner from the magnetic pickup 20 is then passed through a signal conditioner 22 which transforms the input signal into a short duration pulse (approximately 10 microseconds), which is compatible with the rest of the system.
m is signal is then used to turn on the RPM binary counter 23 to start counting pulsations being produced by the crystal oscillator 24. The circuit will then measure the time interval for two complete revolutions of the harmonic da~per 15 which is eguivalent of two revolutions of the engine. This is accom-plished by a control unit 27 which turns on the RPM binary counter 23 when a top dead center signal is sensed. The counter continues to count pulsations of the frequency produced from a frequency divider 28 which is driven by the crystal oscillator 24, until two revolutions of tne harmonic damper are completea, the completion of which is signaled by another top dead center signal. The result of this count of pulsations is stored in the RPM binary counter 23 and is proportional to the value of X above.
Since we are concerned with a four-stroke cycle engine, during the two revolutions of the engine just measured, the number one spark plug must have fired once. For an ad-vanced ignition system, the spark firing sign~1 will occur slightly before top dead center, and for a reb~bd ignition system the spark firing signal will occur slightly after top dead center. The circuit measures the number of pulsations occurring between the spark plug firing and top dead center tfor advanced timing). This is acco~plished by the control unit 27 which turns on the timing binary counter 30 when the ~park firing signal from the wire loop r coil, or clip 32 is sensed, and turns the ti~ing binary counter 30 off when the top ; - 17 -.. :

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~103~452 ~-dead center signal is sensed. During the interval that the ti~ing binary counter 30 is turned on, it counts the pulsations of the frequency produced from the frequency di~ider 28 which is driven by the crystal oscillator 24. This count of pulsations is proportional to the value of Y needed in ~le above formula.
The actual timing angle computation in this embodi-ment of the invention is then performed. The register 29 is cleared, the contents of the timing binary counter 30 is applied to the input of the adder 33. This number is added a number of times proportional to 720 to the contents of the register 29 via the adder 33 and the resulting new answer is olaced in the register 29, the number of additions being counted by the multiplying counter 34. The previously stored contents of the -RPM binary counter 23 is applied to the input of the adder 33 in it-~ negated form. This number is added to the contents of the register 29 via the adder 33 with the result being placed in the register 29. If the register 29 now contains a positive non-zero number, one pulse is counted by the timing binary coded decimal (BCD) counter 35. This process is repeated as long as the register 29 contains a positive number. ~Ihen this process stops, the timing BCD counter 35 then contains the result of the multiplication of the constant by Y and then that quantity being divided by X which then equals 720 Y, which is the timing angle. ~ timing angle display 36 is provided to give a visual readout of the timing angle so obtained If the spaxk plug fires before top dead center, the positive indicator light on the timing angle display 36 will show the engine as running in an advanced spark condition.

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If the top dead center signal comes before the spark plug - fires, the engine is running in a retarded cond~on and the negative indicator light will signal this condition.
If it is desired to time the engine in a retarded condition, the time duration between top dead center and ~park plug firing is still a positive nu~ber and the calcula-tions are all performed in exactly the same manner a~ above.
Now, referring specifically to Figure 7, ~liS
figure shows the same system as shown in Figure 6 with the additional apparatus needed to calculate the RPM.
The RPM of the engine is calculated by dividing 60 (the nu~ber of seconds in a minute) by the time in seconds for one revolution of the engine. This can be represented by the mathematical equation; ~PM = 120, where X represents - the time for two revolutions of the engine.
In the present embodiment of the invention, the actual RPM calculation using the above formula is done as follows : The register 29 is cleared and a number proportional to the constant 120 is added to the register 29 via the adder 33, with the resulting answer being put back in the register 29. m e previously stored contents of the RPM binary counter 23 is applied to the adder 33 in its negated form. This negated number is added to the register 29 via the adder 33, with the resulting answer placed in the register 29~ If the register 29 ncw contains a positive, non-zero number, one pulse is counted in the RPM binary coded decimal (BCD) counter. This process is repeated as long as the register 29 contains ~ .

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a positive number. The RPM BCD counter 39 will now contain the result of the division of the constant divided by the contents of the ~PM bin~ry counter 23 which is equal to 20, which is the RPM of the engine.
It should be understood that in both of these cal-culations, the actual circuitry and numbers used ~herein have been scaled to minimize the amount of circuitry and approxi-mately maintain the same degree of resolution throughout the circuit. Therefore, numbers that are proportional to the constants in the previously cited formulas are used rather than the actual numbers.
Referring specifically to Figure 8, an RPM display 41 i5 provided to give a visual readout of the P~M of the engine. Also, the results of the RPM calculation are applied to the ~PM comparator 42 which compares the contents of the XPM ~CD counter 39 to predeterminad lower and upper limits.
If the number is not within these limits, the timing compara-tor 43 is disabled by the lockout relay 40 and the timing angle display is blanked out. If the RPM is within prede-termined li~its, a timing angle comparator 43 compares thecontents of the timing BCD counter 35 to lower and upper limits and illuminates one of the appropriate indicator lights 44 to indicate whether the timing is high, low, or in band, and if needed also energizes one of the appropriate relays to drive the servo-mechanism 37 in the appropriate direction to adjust the distributor 38 to produce a desired value of the timing angle.
One of two relays would be energized. $f the timing angle were too high, the high value reiay 45 would be activated and would activate the servo-mechanism 37 so as to '' ' ' , ' '~

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rotate the distributor 3B in~~e~-appropriate direction to lower the timing angle, at which time the calculation and comparison process would start anew to see whether the new value of the timing angle is in band. If the timung angle i~ too low, the low value relay 46 would be activated in such a manner as to have the servo-mechanism 37 rotate the distributor in the opposite direction, thus raising the timing angle, with the same recalculation and recomparison process again following.
The above process, when complete, has calculated the timing angle and RPM, compared the RPM with a desired range and if the RPM is in the desired range, used the value of the timing angle to adjust the distributor to obtain a desired ti~ing angle.
The servo-mechanism and its control circuitry may be eliminated and the adjustment done by hand if the system is used manuaily.
An engine simulation test which can be selected by the mode switch 47 supplies through the frequency divider pulses representing top dead center and spark to be used in place of the signals coming from the signal conditioners 22.
Under these conditions, specific numbers- should be displayed on the timing angle display 36 and on the RPM display 41.
m is provides for an easy internal self test to check the operation of the unit.
Also, if a more stable result from the system is desired, instead of performing ~e timing and RPM calculation ~ -over two revolutions of the engine, it may be performed over .~ .

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- a larger number of revolutions. I prefer to use powers of the number 2 (i.e. 2Z, where z = 0, 1, 2, ...~) since the system performs its mathematical computations in the binary system, which is based on the number 2. A number of averages, such as 4 or 8, can be selected by the num~er of averages switch 48.
It should be understood that measuring ~le number of pulsations througA two full and exact revolutions of the engine may be done between spark firings, since that equals two revolutions of the engine.
Figure 9 shows the damper 50 provided with the slot 51, and having a bulb 52 providing a light signal to affect a light sensor, such as a phototransistor 53, to provide a-top dead center signal.
Figure 10 shows another modification of the harmonic damper. The damper 54 ~ ~ided with a hole 55 having an electric light 56 on one side and a light sensor on the other side.
Figure 11 shows the spark plug 31 having a metal tu~e 60 provided on the top of the spark plug to non-inductively :
receive the spaxk signal and convey it to the signal conditioner 22 through the wire 61.
Figure 12 shows use of a resistor 62 to take the place of the spark plug, one side of the resistor 62 being grounded, the singal beins transmitted to the signal conditioner through the wire 63.
Fisure 13 shows a wire loop, clip, or coil 32 around the spark plug wire 26 to inductively pro~uce the spark firing signal when the spark plug 31 fires.

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Figure 14 shows the distributor points 64 producing the signal to the signal conditioner 22.
Applicant has also found that in many cases, it is desired to have the true average timing angle over all the cylinders of an internal combustion engine. This is due to the fact that it has been found as a result of the extensive testing done on internal combustion engines due to recent emissions control laws, that even though you have the number one piston set at its top dead center position, due to tolerance stack-up the journals of the crankshaft, and, ~lere-fore, the pistons in the other cylinders will not be exactly 90 apart, thereby causing the spark firings in the other cylinaers to occur at other than ~leir ideal times. This is further ag~ravated by tolerance stack-ups in other engine parts; such as the distributor, etc.
~ have found that the difference betMeen the average timing angle of all the cylinders in a V-8 internal combu~ion engine, and that of the nu~ber one cylinder alone, can be as much as 1. This can be a significant factor in the amount of emissions produced in any given engine, and therefore the true average timing angle has become an im~ortant piece of information in the art.
While attempts to find the true average timing angle are old in the art, and many devices are on the market which purport to find the true average timing angle over all the`
cylinders of an internal co~bustion engine, none of them can meet the present day requirements for accuracy.
This stems from the fact that all such devices until the present time have had an inherent inaccuracy built in to them because they assume engine speed constant, which as `~
mentioned previously, it never is~
I have adapted the method and apparatus just ..

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described for finding the true spark advance in one selected cylinder, to find the true average spark advance over all the cylinders of an internal combustion engine, all without assuming engine speed constant.
I do this by obtaining a time value for the true spark advance of each cylinder in the selected engine. I
then add these time values together and divide by the nun~er of cylinders involved to get a true average spark advance time; dividing the time just obtained by the tim2 ~he engine takes to rotate one degree gives you the true average spark ad~ance over all the cylinders in the selected engine in degrees.
It should be understood that while for purposes of illustration a V-8 engine is shown, ~y invention will work equally as well on a 4 or 6 or other number cylinder engine, whether reciprocating or rotary, with appropriate changes in the equations discussed below, and will do so irregardless - of whether the engine is equipped with a conventional spark ignition system or any of the great variety of solid state ignition systems now being installed on engines as standard equipment or sold as an after-market replacem.ent. It should - also be understood that, although for convenience in keeping the circuitry involved to a ~inimum, Applicant chooses to pick up a signal from the coil wire, the ~easurement of the true average timing angle may be performed just as well by pic~ing a signal up from each spark plug on the engine as it fires or any other appropriate place, depending on the particular engine being tested.
Referring to Figure 16 which shows graphically h~w Applicant's invention is applied to a V-8 engine running in an .

~038~5Z
advanced spar~ condition, it can be seen that during two

(2) revolutions of the engine, each spark plug of the ~ 8 engine must have fired at least once. Each firing of a spark plug is represented as a coil pulse, as shown in Figure 16.
It should be understood that while the coil pulses are numbered from one to eight, in this case the number does not represent the nurber of the cylinder where the spark firing occurred as it did when we were concerned with the true spark advance of one cylinder, but instead it represents the order of the spark firings during the two revolutions I chose ~o measure. For example, the number one coil pulse would represent the spark firing of the first cylinder I chose to measure, even though, using the standard numbering system for a V-8 engine it might have occurred in the number four cylinder.
When you are finding an average spark advance over ;; ~ -all eight cylinders, as long as you measure ~he spark advance of all the cylinders once during t~Jo revolutions, it makes no difference s~here you start.
Since, during two (2) revolutions of engine, which . . .
e~uals 720 of rotation, each spark plug must have fired once, ~t is easily seen that this means that in a V-8 engine a spark plug will ideally fire every 90. Therefore, the distance between each coil pulse shown in Figure 16 represents the ti~.e the engine takes to rotate 90.
Since each coil pulse represents a spark plug firins, it can be seen that for the situation where the engine is running in a condition such that the ignition is advanced, the time interval between the last coil pulse occurring during ~, .
;. ....

- , , ~ ~ .

~ 038452 the previous two revolutions of t~e engine, indicated ~y the numeral eight, since there are eight spark occurrences in two revolutions, and the first top dead center (TDC) pulse indicated by the numcral 1 in Figure 16 represents tne time interval bet~teen the last spark plug firing and the pistor. in the respective cylinder reachins its top dead center position or, in other words, this tim~ represents the spark advance of the last ~park plug to fire in the previous t~Jo revolutions.
I now chose this ti~e interval as one of eight time intervals which I will measure during two rev~lutions of ~le engine.
Therefore, to measure the spark advance of all eight cylinders I must find the values of Al, A2,A3, A4, 5~ 6 7 8 While I could have an apparatus which would measure a value for the time which the engine takes to rotate until each spark plug fires, measured from a sele~ted startlng point, and then subtract from the value so measured for each cylinder, -the time the engine took to rotate ~from the last occurring TDC pulse, to the spark firing in question and thereby obtain the- values for Al~ ~2' A3~ A4~ As~ A6, A7 and A8~ means to do this are somewhat complicated, and not necessary, when by looking at the mathematical equations which can be derived from Figure 16,. it can be seen that much simpler formula can be used, with no loss of accuracy, : The value of Al can also be represented by the time the engine takes to rotate 90, minus the time interval bet~reen the first TDC pulse and the time the engine takes to rotate tothe first spark plug firing, or Al = 90 -tl, or 103~4S~
by substituting the time the engine takes to rotate two (2) revolutions, represented by the capital letter X, Al =
X/8 - tl.
Since the second ~park firing will ideally occur at a time when the engine has rotated to a position 90 farther than when the first spark firing occurred, it can be seen that this second spark firing (represented ~y the number 2 coil pulse in Figure 16) takes place at a time 180 - t~, or as in a manner similar to above, is equal to 2X/8 - t2~ which equals A2, the true spark advance of the second cylinder to fire.
- In a similar fashion, the spark advance for ead cylinder can be foun,d by performing similar steps to get the value of A3, A4, A5, A6 and A7, and finally arriving with the value of A8 equal to 4X/8 - t8. If we let Z equal the average spark advance for all eisht (8) spark plug firings, then : :
~lj Timing Angle = X (720). With X = time for two revolu-tions of the engine~ as before.
Substituting the value of Z.in this formula and simplifying :
.
wherever possible we arrive with the formula : :
(2) Z - ltX/8 - t~) + (2X/8 - t2) + 13X/g - t3) + (4Y/8 - t4) i :
+ (X/~ - t5) + (2X/8 - t6) + (3X/8 - t7~ + (4X/8 - t8)]/8.
Simplifying further we arrive at the formula :
~3) z - -(t + t2 + t3 + t4 + ts + t6 + t7 + t8)/8+(2 / )/
Substituting this value of Z in our formula (1~ above we arrive at :
g g 1 (tl t2 t8 + t4 + ts + t6 + t7 + t8) /8 + 5X/16~ 720.0 ~ : .
X
After simplification we come up with the formula : -t5) ~iming Angle - -(tl + t2 + t3+t4 +t5 +t6 + ~ + t8)90/X
225.00.

,~ - 27 -10;~84S2 ~ he formula will remain exactly the same should ~ e engine be running in a retarded spark condition, except the value of the timing angle in the formula :

( 1 t2~ t3+ t4+ ts+ t6+ t7+ t8)90/x+22s o would turn out to be a negative num~er.
It can n~ be seen that only one set of values, ~he 1 2, 3~ 4~ ts, t6~ t7 and t8 need now be r,easured rather than the two sets mentioned absve.
Similar equations can be derived for six cylinder and four cylinder engines, such that only the values of t need be found~
If the graphs were to be set up and the formulas derived in a manner similar to that followed above, or a six cylinder engine having a star-shaped crankshaft, you would derive the following formula for timing angle :
(6) Timing Angl~ = - (tl+ t2+ t3+ t4l t5l t6)120/X + 240 If the formula for a four cylinder engine having a flat crankshaft were desired, you would arrive at:
(?) Timing Angle - - (tl+ t2+ t3+ t4)l8ox + 270 Other formulas may be worked out for engines with othe:
cylinder arrangements, or for rotary engines.
It should be understood that although the various value for spark advances Al, A2, A3, A4, A5! A6~ A7 and A8 appear to be exactly identical in the graphs of Figures 16 and 17, in reality,~due to tolerance stack-ups and the like, each of these values will be slightly different, However, this value is impossible to show accurately on drawings of the present scale.

,. _ Referring to Figures 18 and 19, the TDC signal obtained in a manner similar to that just described for measuring the timing angle of one cyliner, from the magnetic pick-up 20, is passed through ~ie signal conditioner 22, which - transforms tlle signal into a short duration pulse (approxi-mately 10 mucro-seconds) which is compatible Witil the rest of the system.
This s~gnal is then used to turn on the RP~ binary counter 23 to start counting pulsatlons being produced by the crystal oscillator 24. ~he circuit will then measure the time interval for two (2) complete revolutions of the harmonic damper 15, which is equivalent to two ~2) complete revolutions of the engine. This is accomplished by a control unit 27 ~i which turns on the RPM binary counter 23 when a top dead center signal is sensed. The counter continues to count pulsations of the frequency produced from a frequency divider 28, which is driven by the crystal oscillator 24 until two (2) revolutions of the harmonic damper are completed, the i~;
completion of which is signaled by another top dead center signal. ~he result of this count of pulsations is stored in the RPM binary counter 23. ~hen measuring the true average timing angle over all eight cylinders of an internal com-bustion engine, the circuitry is set up as ~own in Figure 18 and includes a second regigter 68 and a second timing binary counter ? which were not present when performing the measurement of the timing angle for a single cylinder, but are necessary in finding the true average timing angle j-~
over all eight (8) cylinder~ for the reasons which wil} be explained below.

' .. .. .. .

- .. ~ . ,....... . . : .
. . . . . . , . ~ .. . ~ .

1038~S2 Si~ce we are concerned here with a V-8 four-stroke cycle engine with an advanced ignition system, the TDC pulse from the magnetic sensor 20 also turns on the ti~ing binary counter 30. At the occurrence of the first coil pulse, the contents of the timing binary counter 30 are transferred to the second register 68. Note that timing binary counter 30 has not been turned off, kut continues to operate and has ~ust been read at a certain point in time. This number obtained is added to the contents of register 29, via the adder 33, with the result being placed in the register 29.
Thi-~ now gives us the value of tl. ' For the 2nd, 3rd and 4th spark plug firings, which are represented by the numbers 2, 3 and 4 in Figure 16, the same process is repeated. At the occurren~e of the second coil pulse, the contents of the timing ~inary counter 30 are ~gain transferred to the second registex 68, the contents of the second register 68 are added to the contents of the -register 29, via the adder 33, with the resulting answer placed in register 29.~ This now gives us the sum of tl ~ t2.
At the occurrence of the third spark firing, represented by the number 3 in the graph of Figure 16, the contents of the timiny binary counter 30 are again transferred to the second register 68. The contents of the second register 68 are added to the contents of register 29, via the adder 33, with the resulting answer aqain placed in register 29.
Thi8 now gives us the sum of tl t t2 + t3-.

~03845Z
When the fourth spark firing occurs, represented by the number 4 coil pulse in Figure 16, the contents of the timing binary counter 30 are again transferred to the second resister 68, the cont~nts of the second register 68 are added to the contents of register 29, via the adder 33, with the resulting answer placed in register 29. This now gives us the sum of tl+ t2+ t3+ t4. The timing binary counter 30 is now turned off.
The second TDC pulse from ~le magnetic pick-up 20 (see Figure 18) now occurs and turns on the second timing binary counter 70. The same process just described for obtaining the sum of tl+ t2+ t3+ t4 is now repeated to obtain the sum of t5+ t6+ t7+ t8, except that the second timing binary counter 70 is used, instead of the timins binary counter 30. Therefore, the register 29 now contains the sum of tl+

t2~ t3+ t4+ ts+ t6+ t7+ t8 If engines were always found to be running in an ~dvanced spark condition, the use of the second timing binary counter 70 would not be needed, and all the values of tll t2+
t3+ t4+ *5+ t6+ t7+ t8 could be found u$ing timing binary counter 30.~ However, the use of the second timing binary counter 70 is necessitated by the conditions brought about if the engine happens to be running in a retarded spark condition. As shown in Figure 17, tSe fact that the second TDC pulse will now occur before the 4th coil pulse, will cause th~e time interval t4 to be cor.pleted after the ~easurement of the time intervals t5, t6, t7, t8 has already started, and it can be seen that if only one timing binary - : .

' . ~ .-, .

~ 31 -counter was used, you would have the impossible situation where one timing binary counter would be attempting to count two different values simultaneously~ Therefore, the use of two timing binary counters is desirable in order to enable my invention to be operable regardless of the con~ition in which the test engine is found, and still get the optimum accuracy. Any c~anse in the starting point of t,he measurement of the time intervals tl, t2, t3, t4, tS~ t6, t7 and t8 would decrease the accuracy of the system.
The next step in the performance of the calculation is to preset the timing BCD counter 3~ to a + 225 to account for the constant in the timing angle formula. It should be understood that in this e~odiment of the inventior., an up-down (bi-directional) timing BCD counter is used, that is, a counter which has the capability of counting either up or down, and also ha~ the capability of being reset to zero, or being preset to some non-zero nu~ber, in-this case + 225. Counters s~uch as this are well known in the art and need not be described in detail herein.
.
Now ~lat we have the sum of tl+ t2+ t3+ t4+ t5+ t6+
t7+ t8, it can be seen that the next step in the equation is to multiply the sum~of tl+ t2+ t3+ t4+ t5 t6 7 8 constant 90. This is accomplished by transferrinq tne contents of the register 29 to the second register 68. The resister 29 i~ *en ~set to zero. The contents of the second register 68 is added to the contents of register 29 via the adder 33, with the resulting value placed in register 29. This operation is repeated 90 times, at whicil time the multiplying counter 34 signals its completion.

~ 32 -- . _ ~03~4SZ
We have thus added the sum of tl+ t2+ t3~ t4+ t5+
t6+ t7+ t8 to itself 9~0 ti~es, or in other words, we have multiplied it by 90.
The next step is to divide this result by the time the engine takes to ro~ate 720, represented by the letter X.
This number is now contained in the RP~i binary counter 23.
The contents of the RP~I binary counter 23 are applied to the input of the adder 33 in its negated form. This number is added to the contents of the register 29, via the adder 33, with the result being placed in the register 29. If register 29 now contains a positive non-zero number, one pulse is counted by the timing binary coded decimal (BCD) - counter 35, this process is repeated as long as the register 29 contains a positive number. When this process stops, we have completed the division by the variable X. The timing BCD counter 35 counted down this number of pulses, which represents the division.
Since the timing BCD countqr 35 was originally preset -to + 225, when we have counted down the number of pulses equal to the division first performe,d, we have then completed the calculations involved in the equation: Timing Angle =
[tl+ t2+ t3+ t4+ t5 + t6+ t7+ t8)90/X + 225.0 and now have the true average timing angle over the eight cylinders of a V-8 internal combustion engine. In a manner similar to tihat described in the method for finding the true timing angle in one selected cylinder, a timing angle display 36 is provided to give a visual readout of the timing angle so obtained.
~he RPM of the engine is calculated by dividing 60 `~
(the number of seconds in a minut~) by tile time in seconds for one revolution of the engine. Again, this is represented -....

, !

- 1~)38452 - by the mathematical equation RPM = 120, where X represents the time for two revolutions of the engine.
In the present e~bodiment of the invention, the ~ctual RPM calculation using the above for~ula is aone as follows : The register 29 is cleared, and a nu~ber pro-portional to tne constant 120 is added to the register 29, via the adder 33, with the resulting answer put back in the register 29. The previously stored contents of the RPM
binary counter 23 is applied to the adder 33 in its negated form. This negated number is added to the register 29, via the adder 33, with the resulting answer placed in the register 29. If ~he register 29 now contains a positive non-zero number, one pulse is counted in the RP~I binary coded decimal ~BCD) counter 39.~ This process is repeated as long as the register 29 contains a positive number. The RPM BCD counter 39 ~ill now contain the result of the division of the constant, divided by the contents of the RPM binary counter 23, which is equal to 120, wh-ch is the RPM of the engine.

i As was the case in the previously described cal- -culation of RP~ in the system which found the timing angle of one selected cylinder of an internal combustio~ engine, the actual circuitry and nu~ers used herein have been scaled to minimize the amount of circuitry required, and maintain approximately ~he same degree of resolution throughout the circuit. Therefore, numbers that are proportional to the constant in the previousl~ cited~ formula are again used, rather than the actual numbers.

.
10384~5Z - ~
PRferring specifically to Figure 19, in a manner similar to that described before, an RPM display 41 is provided to give a visual readout of the RPM of the engine.
Also the results of ~le RP~I calculation are compared by t~e RP~ comparator 42 which compares ~he contents of the r~M
BCD counter 39 to predetermined lower and upper li~its. ~s before, if the number is not within these limits, ',he timing comparator 43 is disabled ~y the lock-out relay 40, and the timing angle display is blanked out. If the RPM is within - 10 predetermined limits, a timing angle comparator 43 compares the contents of the timing BCD counter 35 to lower and upper limits and illuminates one of the appropriate indicator lights 44 to indicate whether ~he timing is hish, low, or in band, and, if needed, also energizes one of tne appropriate relays to drive the servo-mechanism 37 in the appropriate direction to adjust the distri~utor 38 to produce a de~ired va'u2 of the timing angle.
- One of two relays w~ould be energized. }f the timing angle were too high, the high value relay 45 would be energized -and would activate tne servo-mechanism 37 so as to rotate the distributor 38-in the appropriate ~direction to decrease -~
the timing angle, at which time the calculation and comparison ~ -process would start anew to see whether the new value of the timing value is in band. ~If the timing angle is too low, the low value relay 46 would beenergized in such a manner as ~ -to have tne servo-mech-anism 37 rota~e the distributor in the opposite direction~ thus increasing the ti~ing angle, with ~ ;~
the same recalculation and recomparison process again following.
;,~ ' : ~f .

~03845Z
The above process, when complete, has calculated the true average timing angle and RPM, compared the P~l with a desired range, and if the ~PM is in the desired ranse, used the value of the timing angle to adjust th~ distributor to obtain a desired timing ansle.
As was the case in the apparatus previously des- -cribed for finding the timing angle of one selected cylinder, the servo-~echanism and its control circuitry may be eliminated and the adjustment done by hana if the system is used ~anually.
~he circuitry in Figure l9 also show~s ~le necessary --apparatus needed if it is desired to have a system which can operate either to find the timing angle in one selected cylinder, or to find the true average timing angle over all cylinders of an internal co~bustion engine. In order to accomplish such dual operation, an additional switch 75 is provided, which will adapt the system either for accepting an i~pulse from the number one spark plug through the lead wire 76, or accepting an impulse from the coil wire 77, when ,the lead 76 is placed thereon, instead of on t~e spark plug - 20 26. Mhen the swit~h is in the position marked coil, the lead wire 76 must be placed on the coil wire 77, and when the switch 75 is in the numbe~ one plug position, the lead wire 76 must be attached to the spark plug wire 26, leading to the number one spark plug 31.
Also provided in the dual system shown in Figure 19 ~s the mode switch 47~to select between the run mode ana test mode for the purposes previow ly described.

,.
.

1038~5Z
me number of averages switch 48 is again provided.
However, in the system which can find the timins angle of one selected cylinder, and also the true average timing angle over all the cylinders, its operation is somewhat different than that previously described.
when the switch 75 shown in Figure 19 is set to its numDer one plug po~tion, tne number of averages switch 48 works exactly in the same manner as previously descxibed.
However, when the switch ?s is in the coil position, the number of averages switch finds the timing angle value by averaging not readings of a single cylinder, as before, but by averaging 2, 4, 8, etc. complete cycles of the machine.
~n other words, the apparatus would find the true average timing angle of the test engine 2 or more separate times, it would then average the different values obtained and display this number on the timing angle display.
As before, the apparatus shown in ~igure 19 may be used manually, outside an automated stand, as shown in Figure 15, or may be incorporated into a stand similar to Figure 4.
~he present invention may also be used on engines which have a solid state ignition systemO Although many ~ariations of solid state ignition systems are available ~ -today, and all of them cannot be shown here, a solid state system whicll is in wide use today may be illustrated as shown in Figure 20, with the bo:: numbered 85, representing the various components~of the solid state system, which are ;
well known in the art and need not be described in detail -~
herein.

,.
~ .

, . .. .. . . ..... . , ~,_ The solid state ignition system 85 has a coil wire 77 connected to the distributor 38. A spark firing signal is picked up from ~le coil ~ire 77 by ~he lead wire 76, with the remaining operation of the system iaentical with that just described. The con~ents of ~he cabinet of Figure 20 are identica with that shown in the dotted-line portion labeled cabinet in Figure l9.
If the solid state ignition system is not of the type ;
illustrated in Pigure 2Q, the lead wire 76 would be attached to the system in a suitable position to pick up a spark firing signal, and would use such signal in the manner previously described. Suitable changes in the control circuitry may be made if necessitated by the particular nature of ti~e spar};
firing signal picked up.
There is thus provided an improved testing system for internal combustion engines ~7hereby the objects of the present invention listed above and numberous additional advantages are attained.

.

- 3~ -. ..

Claims (35)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of revealing the average timing angle over all the cylinders of an internal combustion engine with reference to a single predetermined top dead centre position, said engine including a distributor, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston; said method including measuring the time the engine takes to rotate two full and exact revolutions from top dead centre to top dead centre from said predetermined top dead centre position determining simultaneously with the measurement of the time taken by the engine to rotate said two revolutions the time of advance with reference to said top dead centre posi-tion for each individual cylinder in the engine summing these time intervals for each individual cylinder, dividing the values so obtained by the number of cylinders in said engine, thereby obtaining an average time of advance, determining the time said engine takes to rotate one degree during said two revolutions, and dividing the average time value just obtained by the time the engine takes to rotate one degree, thereby obtaining the true average timing angle.

2. The method defined in Claim 1, with said internal combustion engine being equipped with a solid state ignition system.

3. The method defined in Claim 1, with the summation being obtained by measuring the time which the engine takes to rotate to the point of spark firing in each respective individual cylinder, said time being measured from the time of occurence of the spark firing closest preceding the time the engine was last at a top dead center position, and subtracting from each individual time so recorded, the time since the engine was last at a top dead center position, thereby obtaining a true spark advance for each cylinder, and summing the values so obtained, thereby obtaining said summation.

4. The method defined in Claim 1, with the time required for one degree of engine rotation being determined by producing electrical pulsations of a uniform frequency by means of an oscillator, counting the pulsations so produced by the oscillator during two revolutions of the engine, relating the number of pulsations so counted to the time elapsed, and dividing the elapsed time by 720 to determine said time for one degree of rotation.

5. The method as defined in Claim 1, with the engine running in a retarded spark condition, measuring the time which the engine takes to rotate two full and exact revolutions from top dead renter to top dead center, simultaneously measuring for each individual cylinder in said engine the time the engine takes to rotate from the moment the piston in each respective individual cylinder reaches its top dead center position to the time of occurrence of spark firing in the respective individual cylinder, summing the individual time intervals so obtained for each individual cylinder, dividing the value so obtained by the number of cylinders in said engine to obtain an average time, de-termining from the number of pulses just counted for two revolutions the time the engine takes for one degree of rotation, and dividing said average time just obtained by the time the engine takes to rotate one degree, thereby obtain-ing the true average timing angle over all the cylinders of said engine.

6. The method defined in Claim 5, with said summation being obtained by measuring and recording for each individual cylinder in said engine the time the engine takes to rotate to the point of spark firing for each individual cylinder, said time being measured from the time of occurrence of the spark firing closest succeeding the time the engine was last at a top dead centre position, and subtracting from each individual time so recorded the time since the engine last reached said top dead centre position, thereby obtaining a true spark advance for each cylinder, and summing the values so obtained, thereby obtain-ing said summation.

7. The method defined in Claim 5, with the time re-quired for one degree of engine rotation being determined by producing electrical pulsations of a uniform frequency by means of an oscillator, counting the pulsations so produced by the oscillator during two revolutions of the engine, relating the number of pulsations so counted to the time elapsed, and divid-ing the elapsed time by 720 to determine said time for one degree of rotation.

8. A method of revealing the average timing angle over all the cylinders of an internal combustion engine with reference to a single predetermined top dead centre position, said engine including a distributor, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston, said method including running or rotating the engine and producing, with the aid of an oscillator, voltage pulsations of a predetermined frequency, counting said pulsa-tions for two full and exact revolutions of the engine from top dead centre to top dead centre from said predetermined top dead centre position, determining simultaneously with the counting of pulsations for said two revolutions of the engine the timing advance for each individual cylinder in the engine with refer-ence to said predetermined top dead centre position by deter-mining the difference between the number of pulsations occur-ring during the time the engine takes to rotate from the time of occurrence of the spark firing closest preceding the time the engine was last at a top dead centre position to the spark firing in each individual cylinder being measured, and the number of pulsations occurring from the time the engine was last at a top dead centre position until said spark firing, summing the count of pulses so obtained for each cylinder, dividing said sum by the number of individual cylinders in said engine, deter-mining from the number of pulses just counted for two revolutions the number of pulses occurring during one degree of engine ro-tation, and dividing the number of pulses just obtained by said division by the number of pulses occurring during one degree of engine rotation, thereby determining the true average timing angle over all the cylinders in said internal combustion engine as related to said predetermined top dead centre position.

9. The method as defined in Claim 8, with said engine running in a retarded spark condition, said method including running or rotating the engine and producing, with the aid of an oscillator, voltage pulsations of a predetermined frequency, counting said pulsations for two full and exact revolutions of the engine from top dead centre to top dead centre from said predetermined top dead centre position, determining simultan-eously with the counting of pulsations for said two revolutions of the engine the timing advance for each individual cylinder in the engine with reference to said predetermined top dead centre position by determining the difference between the number of pulsations occurring during the time the engine takes to rotate from the time of occurrence of the spark firing closest succeeding the time the engine was last at a top dead centre position to the spark firing in each individual cylinder being measured, and the number of pulsations occurring from the time the engine was last at a top dead centre position until said spark firing, summing the differences so recorded for each indi-vidual cylinder, dividing said sum by the number of individual cylinders in said engine, determining from the number of pulses just counted for two revolutions the number of pulses occurring during one degree of engine rotation, and dividing the number of pulses obtained by said division by the number of pulses occurring during one degree of engine rotation, thereby determining the true average timing angle over all the cylinders in said inter-nal combustion engine as related to said predetermined top dead centre position.

10. The method defined in Claim 8, with the time re-quired for one degree of engine rotation being determined by producing electrical pulsations of a fixed frequency by means of a crystal oscillator, counting the pulsations so produced by the crystal oscillator during two revolutions of the engine, relating the number of pulsations so counted to the time elapsed, and dividing the elapsed time by 720 to determine said time for one degree of rotation.

11. The method defined in Claim 9, with the time re-quired for one degree of engine rotation being determined by pro-ducing electrical pulsations of a fixed frequency by means of a crystal oscillator, counting the pulsations so produced by the crystal oscillator during two revolutions of the engine, relat-ing the number of pulsations so counted to the time elapsed, and dividing the elapsed time by 720 to determine said time for one degree of rotation.

12. A method of revealing the timing angle of a V-8 internal combustion engine including a distributor, a coil, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston, said method including running or rotating the engine and producing with the aid of an oscillator, voltage pulsations of a predetermined frequency, producing with the aid of a magnetic pickup a signal each time the piston of a predetermined cylinder is at its top dead center position, counting said pulsations for two full and exact revolutions of the engine, beginning from a first top dead center signal and ending at a second subsequent top dead center signal, having said first top dead center signal simultaneously start a counting device to continuously count and record the number of pulsations being produced, recording the reading on such counting device each time a spark firing signal is produced, obtaining a summation of the eight values so obtained, multiply-ing said summation by the number ninety, dividing the result of such multiplication by the number of pulses counted for two full and exact revolutions of the engine, making the result of such division negative, and adding to the result of such division the number 225, thereby obtaining the true average timing angle of said engine in degrees.

13. A method of revealing the timing angle of a six cylinder internal combustion engine having a distributor, a coil, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston, said method including running or rotating the engine and producing with the aid of an oscillator, voltage pulsations of a predetermined frequency, producing with the aid of a magnetic pickup a signal each time the piston of a predetermined cylinder is at its top dead center position, counting said pulsations for two full and exact revolutions of the engine, beginning from a first top dead center signal and ending at a second subsequent top dead center signal, having said first top dead center signal simultaneously start a counting device to con-tinuously count and record the number of pulsations being produced, recording the reading on such counting device each time a spark firing signal is produced, obtaining a summation of the six values so obtained, multiplying said summation by the number 120, dividing the result of such multiplication by the number of pulses counted for two full and exact revolu-tions of the engine, making the result of such division negative, and adding to the result of such division the number 240, there-by obtaining the true average timing angle of said engine in degrees.

14. A method of revealing the timing angle of a four cylinder internal combustion engine having a flat crankshaft and including a distributor, a coil, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston, said method including running or rotating the engine and producing with the aid of an oscillator, voltage pulsations of a predetermined frequency, producing with the aid of a magnetic pickup a signal each time the piston of a predetermined cylinder is at its top dead center postion, counting said pulsations for two full and exact revolutions of the engine, beginning from a first top dead center signal and ending at a second subsequent top dead center signal, having said first top dead center signal simultaneously starting a counting device to continuously count and record the number of pulsations being produced, recording the reading on such counting device each time spark firing signal is produced, obtaining a summation of the four values so obtained, multiplying said summation by the number 180, dividing the result of such multiplication by the number of pulses counted for two full and exact revolutions of the engine, making the result of such division negative, and adding to the result of such division the number 270, thereby obtaining the true average timing angle of said engine in degrees.

15. A method of revealing the timing angle of a V-8 internal combustion engine running in the advanced spark condition including a distributor, a coil, a plurality of cylinders each having a piston, a spark plug, and a crankshaft connected to said piston, said method including running or rotating the engine and producing with the aid of an oscillator, voltage pulsations of a predetermined frequency, producing with the aid of a wire loop, coil, or clip around the coil wire, a signal each time a spark firing occurs within a cylinder of said V-8 engine, producing with the aid of a magnetic pickup a signal each time the piston of a predetermined cylinder of said engine is at its top dead center position, counting said pulsations for two full and exact revolutions of said engine beginning from a predetermined top dead center signal, con-tinuing through a first subsequent top dead center signal and ending at a second subsequent top dead center signal, having said predetermined top dead center signal simultaneously start a counting device to continuously count and record the number of pulsations being produced since the occurrence of said pre-determined top dead center signal, recording the reading on said device each time a spark firing signal is produced, thereby recording the number of pulses occurring for the first four spark firings, at said first subsequent top dead center signal turning on a second counting device to count and record the number of pulsations being produced, recording the reading on said second counting device each time a spark firing signal is produced and thereby obtain the number of pulses occurring between said spark firing and the last occurring top dead center pulse for each cylinder in said V-8 internal combustion engine, and subtracting each value so obtained from the time interval elapsed from the time of occurrence of the spark firing closest preceding the time the engine was last at a top dead center position, to the occurrence of the respective spark firing, thereby obtaining the spark advance of each cylinder in said engine, summing the individual count of pulses so obtained for each individual cylinder, dividing the value so obtained by the number of cylinders in said engine to obtain an average count of pulses, converting said count of pulses into a time value, determining the time the engine takes for one degree of rotation, and dividing said average time just obtained by the time the engine takes to rotate one degree, thereby obtaining the true average timing angle of all the cylinders of said engine.

16. The method defined in Claim 15, with the time required for one degree of engine rotation being determined by producing electrical pulsations of a uniform frequency by means of an oscillator, counting the pulsations so produced by the oscillator during two revolutions of the engine, relating the number of pulsations so counted to the time elapsed, and dividing the elapsed time by 720 to determine said time for one degree of rotation.

17. A method of revealing the timing angle of a V-8 internal combustion engine running in the retarded spark condition and including a distributor, a coil, a plurality of cylinders each having a piston, a spark plug, and a crank-shaft connected to said piston, said method including running or rotating the engine and producing with the aid of an oscillator, voltage pulsations of a predetermined frequency, producing with the aid of a wire loop, coil, or clip around the coil wire, a signal each time a spark firing occurs with a cylinder of said V-8 engine, producing with the aid of a magnetic pickup a signal each time a piston of a predetermined cylinder of said engine is at its top dead center position, counting said pulsations for two full and exact revolutions of said engine beginning from a predetermined top dead center signal and ending at a second subsequent top dead center signal, having said predetermined top dead center signal simultaneously start a counting device to continuously count and record the number of pulsations being produced since the occurrence of said predetermined top dead center signal, recording the reading on said device each time a spark firing signal is produced by a spark plug firing, thereby recording the number of pulses occurring for the first four spark firings, at said first subsequent top dead center signal turning on a second counting device to count and record the number of pulsations being produced, recording the reading on said second counting device each time a spark firing signal is produced, and thereby obtaining the number of pulses occurring between said spark firing and the last occurring top dead centre pulse for each cylinder in said V-8 internal combustion engine, and subtracting each value so obtained from the interval elapsed from the time of occurrence of the spark firing closest succeeding the time the engine was last at a top dead centre position to the occurrence of the res-pective spark firing, thereby obtaining the spark advance of each cylinder in said engine, summing the individual count of pulses so obtained for each individual cylinder, dividing the value so obtained by the number of cylinders in said engine to obtain an average count of pulses, converting said count of pulses into a time value, determining the time the engine takes for one degree of rotation, and dividing said average time just obtained by the time the engine takes to rotate one degree, thereby obtaining the true average timing angle over all the cylinders of said engine.

18. The method defined in Claim 17, with the time re-quired for one degree of engine rotation being determined by producing electrical pulsations of a uniform frequency by means of an oscillator, counting the pulsations so produced by the oscillator during two revolutions of the engine, relating the number of pulsations so counted to the time elapsed, and divid-ing the elapsed time by 720 to determine said time for one degree of rotation.

19. A device for measuring the true average timing angle over all the cylinders of an internal combustion engine with reference to a single predetermined top dead centre position, said device including means to measure the time the engine takes to rotate two full and exact revolutions from top dead centre to top dead centre from said predetermined top dead centre po-sition, means to determine simultaneously with the measurement of the time taken by the engine to rotate said two revolutions the timing advance with reference to said predetermined top dead centre position for each individual cylinder in the engine, means to obtain a summation of these time intervals for each individual cylinder, means to divide said summation by the number of cylinders in said engine, thereby obtaining an average time, means to determine the the the engine takes to rotate through one degree for the two revolutions just measured and means to divide the time value just obtained by the time the engine takes to rotate one degree, thereby determining the true average timing angle.

20. The device defined in Claim 19 and including means to determine the RPM of the engine on the basis of the time the engine takes to rotate two revolutions.

21. A device for measuring the average timing angle over all the cylinders of an internal combustion engine with reference to a single predetermined top dead centre position, said device including an oscillator adapted to produce by means of a frequency divider electrical pulsations of a uniform frequency, means to produce an electrical signal at the moment of spark occurrence for each individual cylinder in said engine, means to produce an electrical signal at the moment the piston of a predetermined cylinder reaches its top dead centre position, means responsive to said top dead centre electrical signal to begin a first count of said pulsations from the moment said piston reaches its top dead centre position and continuing said first count through a first subsequent top dead centre signal and ending at a second subsequent top dead centre signal, thereby continuing said first count for two full and exact revolutions of said engine, means to convert said first count of pulses into the time for one degree of engine rotation, a first counting means responsive to said top dead centre signal to count the number of pulsations being produced since the occurrence of said top dead centre signal, means responsive to said spark firing pulses to record the reading on said first counting means each time a spark firing signal is produced, a second counting means, means responsive to said first subsequent top dead centre signal to turn on said second counting means, means responsive to said spark firing pulses to record the reading on said second counting means each time a spark firing is produced, and thereby obtaining the number of pulses occurring between said spark firing and the last occurring top dead centre pulse for each cylinder in said internal combustion engine, means to convert the number of pulses so recorded into the time the engine took to rotate between the time of spark firing and the occurrence of the last top dead centre position, means to subtract each time value so obtained from the equivalent of the time interval elapsed from the time of occurrence of the spark firing closest preceding the time the engine last reached a top dead centre position to the occurrence of the respective spark firing, thereby obtaining the spark advance of each cylinder in said engine means to divide the value so obtained by the number of cylinders in said engine, and means to divide said time obtained by the time for one degree of engine rotation during said two full and exact revolutions, thus obtain-ing the true average timing angle.

22. A device for measuring the average timing angle of a V-8 internal combustion engine, said device including an oscillator adapted to produce by means of a frequency divider, electrical pulsations of a uniform frequency, means to produce an electrical signal at the moment of spark occurrence for each individual cylinder in said engine, means to produce an electri-cal signal at the moment the piston of a predetermined cylinder reaches its top dead centre position, means responsive to said electrical signal to begin a first count of said pulsations from the moment said piston reaches its top dead centre position and continuing said first count through a first subsequent top dead centre signal and ending at a second subsequent top dead centre signal, thereby continuing said first count for two full and exact revolutions of said engine, a first counting means res-ponsive to said top dead centre signal to continuously count the number of pulsations being produced since the occurrence of said top dead centre signal, means responsive to said spark firing signals to record the reading on said first counting means each time a spark firing signal is produced, a second counting means, means responsive to said first subsequent top dead centre signal to turn on said second counting means, means responsive to said spark firing pulses to record the reading on said second counting means each time a spark firing signal is produced, and thereby obtaining the number of pulses occurring between said spark fir-ing signal and the last occurring top dead centre pulse for each individual cylinder in said internal combustion engine, means to obtain a summation of the values so obtained for each indi-vidual cylinder, means to multiply said summation by the number ninety and divide the result of such multiplication by the num-ber of pulses counted for two full and exact revolutions of the engine, and means to subtract from the number 225 the result of such division, thereby obtaining the true average timing angle of said engine in degrees.

23. The device defined in Claim 22, wherein said signal responsive means include signal conditioners to convert the electrical pulses into signals compatible with the system, a control unit connected to said signal conditioners to receive these signals, a timing binary counter and a second timing binary counter connected to said control unit, an RPM binary counter also connected to said control unit and a multiplying counter also connected to said control unit, a second resister connected to said control unit, an arithmetic unit consisting of an adder and a register connected to said RPM and binary counters and receiving a signal from said multiplying counter, and a timing binary coded decimal counter connected to said arithmetic unit and adapted to count said pulses and store the result.

24. The device defined in Claim 23 and including a display unit to give a visual read-out of the timing angle.

25. The device defined in Claim 24, and including a selector switch connected to said control unit and adapted to select whether the timing angle will be calculated for one cylinder or over all the cylinders of said engine.

26. The device defined in Claim 24 and including a selector switch connected to said control unit and adapted to select the number of cycles the timing angle will be calculated over.

27. The device defined in claim 26 and including a mode switch connected to the control unit and adapted to perform an internal test of the system.

28. The device defined in Claim 23 and including an RPM binary coded decimal counter.

29. The device defined in Claim 28 and including a display unit to give a visual readout of the RPM of the engine being tested.

30. The device defined in Claim 29 and including a timing comparator to compare the calculated timing angle with a predetermined range of timing angles and display the results of the comparison.

31. The device defined in Claim 30 and including an RPM comparator to compare the calculated RPM with a predetermined range of RPM and blank out, the timing angle display if the RPM is not within the predetermined range.

32. The device defined in Claim 31 and including a servo-mechanism connected to said timing angle comparator and adapted to adjust the distributor to produce desired timing angle.

33. The device defined in Claim 32 and adapted to find the timing angle of a V-8 internal combustion engine equipped with a solid state ignition system.

34. The device defined in Claim 21 and adapted to find the timing angle of an internal combustion engine equipped with a solid state ignition system.

35. A method of revealing the average timing angle over a plurality of cylinders of a multi-cylinder internal com-bustion engine with reference to a single predetermined top dead center position, said engine including a distributor, a plurality of cylinders having a piston, a spark plug, and a crankshaft connected to said piston; said method including measuring the time the engine takes to rotate through a given cycle from top dead center to top dead center from said predetermined top dead center position, determining simultaneously with the measure-ment of the time taken by the engine to rotate through said given cycle the time of advance with reference to said top dead center position for said plurality of cylinders in the engine, summing these time intervals for said plurality of cylinders, dividing the values so obtained by the number of said plurality of cylinders in said engine, thereby obtaining an average time of advance, determining the time said engine takes to rotate one degree during said given cycle, and dividing the average value just obtained by the time the engine takes to rotate one degree, thereby obtaining the true average timing angle of said plurality of cylinders.