INTERNAL COMBUSTION ENGINE IGNITION TIMING INSTRUMENT

• US 3,775,672 A
• Filed: 09/25/1972
• Issued: 11/27/1973
• Est. Priority Date: 09/25/1972
• Status: Expired due to Term

• Current Assignee: Vincent H. Letosky
• Original Assignee: Vincent H. Letosky
• Inventors: Letosky, Vincent H.
• Primary Examiner(s): Lynch, Michael J.
• Application Number:
  US05/291,793
• Time in Patent Office: 428 Days
• Field of Search: 324/15,16,19,16T 73/116-119
• US Class Current: 324/392
• CPC Class Codes: F02P 17/04 dynamically
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Circuitry responsive to a TDC signal, produced when the reference cylinder of the engine is at the top dead center position, and an ignition signal, produced when an ignition spark potential is generated for the reference cylinder, produces a series of timing angle signal pulses of a width proportional to the period between the TDC and ignition signals. An averaging circuit produces a timing angle potential signal of a magnitude proportional to the width of the timing angle signal pulses and of a polarity which indicates whether the ignition spark is retarded or advanced. The timing angle potential signal is applied to a digital voltmeter which indicates directly in degrees the ignition spark retard or advance and is compared with timing angle high and low reference potentials, of respective magnitudes above and below the magnitude of the timing angle potential signal at the selected number of degrees of ignition spark advance or retard, in respective comparator circuits which produce respective output signals indicating whether the ignition spark is retarded or advanced from or occurs at a selected timing angle.

Claims

1. An internal combustion engine ignition timing instrument comprising:

means for prodUcing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude porportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

first circuit means responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

second circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, and logic circuit means responsive to a logic output signal of said selected polarity from both said first and second circuit means for producing a logic output signal of a selected polarity indicating that the ignition spark is advanced;

to a logic output signal of said other polarity from both said first and second circuit means for producing a logic output signal of a selected polarity indicating that the ignition spark is retarded and to a logic output signal of said selected polarity from said first circuit means and a logic output signal of said other polarity from said second circuit means for producing a logic output signal of a selected polarity indicating that the engine is properly timed.

2. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advAnce;

means for producing a direct current timing angle high reference potential signal nad a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

first circuit means responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

second circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, and logic circuit means responsive to a logic output signal of said selected polarity from both said first and second circuit means for producing a logic output signal of a selected polarity upon a first output terminal indicating that the ignition spark is advanced;

to a logic output signal of said other polarity from both said first and second circuit means for producing a logic output signal of a selected polarity puon a second output terminal indicating that the ignition spark is retarded and to a logic output signal of said selected polarity from said first circuit means and a logic output of said other polarity signal from said second circuit means for producing a logic output signal of a selected polarity upon a third output terminal indicating that the engine is properly timed.

3. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance, means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing potential signal at a selected number of degrees of ignition spark retard or advance;

a first comparator circuit responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

a second comparator circuit responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output sIgnal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magniutde of said timing angle low reference potential signal, and logic circuit means responsive to a logic output signal of said selected polarity from both said first and second comparator circuits for producing a logic output signal of a selected polarity upon a first output terminal indicating that the ignition spark is advanced;

to a logic output signal of said other polarity from both said first and second comparator circuits for producing a logic output signal of a selected polarity upon a second output terminal indicating that the ignition spark is retarded and to a logic output signal of said selected polarity from said first comparator circuit and a logic output signal of said other polarity from said second comparator circuit for producing a logic output signal of a selected polarity upon a third output terminal indicating that the engine is properly timed.

4. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means comprising a counter circuit and a NAND gate having an output terminal responsive to said primary signals for producing an ignition signal upon said output terminal of said NAND gate when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

first comparator circuit means responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

second comparator circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal of a selected polarity when the magnitude of said timing angle potential signal is greater than and a logic output signal of another polarity when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, and logic circuit means responsive to a logic output signal of said selected polarity from both said first and second comparator circuits for producing a logic output signal of a selected polarity upon a first output terminal indicating that the ignition spark is advanced;

to a logic output signal of said other polarity from both said first and second comparator circuits for producing a logic output signal of a selected polarity upon a second output terminal indicating that the igniTion spark is retarded and to a logic output signal of said selected polarity from said first comparator circuit and a logic output signal of said other polarity from said second comparator circuit for producing a logic output signal of a selected polarity upon a third output terminal indicating that the engine is properly timed.

5. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

a counter circuit having an input terminal and output terminals, a NAND gate having a plurality of input terminals and an output terminal, means for applying said primary signals to said input terminal of said counter circuit and to one of said input terminals of said NAND gate and means for connecting each said output terminal of said counter circuit to a respective one input terminal of said NAND gate whereby said counter circuit and said NAND gate are responsive to said primary signals for producing an ignition signal upon said output terminal of said NAND gate when an ignition spark potential is generated for the reference cylinder of said engine;

first and second J-K flip-flops each having a clock input and a Q and Q output terminals, first and second NAND gates each having two input terminals and an output terminal, a third NAND gate having an input terminal and an output terminal, means for applying said ignition signal to said clock input terminal of one of said J-K flip-flops and said TDC signals to said clock input terminal of the other one of said J-K flip-flops and means for connecting said Q output terminal of one of said J-K flip-flops and said Q output terminal of the other one of said J-K flip-flop to respective said input terminals of one of said first and second NAND gates and said Q output terminal of said other one of said J-K flip-flops and said Q output of said one of said J-K flip-flops to respective said input terminals of the other one of said first and second NAND gates and said output terminal of one of said first and second NAND gates to said input terminal of said third NAND gate whereby said J-K flip-flops and said NAND gates are responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

an averager circuit responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

first comparator circuit means responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

second comparator circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing anglE potential signal is less than the magnitude of said timing angle low reference potential signal, and logic circuit means responsive to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a first output terminal indicating that the ignition spark is advanced;

to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a second output terminal indicating that the ignition spark is retarded and to a logic output signal from said first comparator circuit and a logic output signal from said second comparator circuit for producing a logic output signal upon a third output terminal indicating that the engine is properly timed.

6. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means responsive to said primary signals for producing a direct current engine RPM potential signal of a magnitude proportional to engine speed;

circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current engine RPM high reference potential signal and a direct current engine RPM low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said enging RPM potential signal at a selected engine speed;

first circuit means responsive to said engine RPM potential signal and said engine RPM high reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said enginge RPM potential signal is less than the magnitude of said engine RPM high reference potential signal;

second circuit means responsive to said engine RPM potential signal and said engine RPM low reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM low reference potential signal;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

third circuit means responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

fourth circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal;

logic circuit means responsive to a logic output signal from both said first and second circuit means for producing a logic output signal indicating that the engine is operating at a speed greater than a selected engine speed;

to a logic output signal from both said first and second circuit means for producing a logic output signal indicating that the engine is operating at a speed less than the selected engine speed and to a logic output signal from said first circuit means and a logic output signal from said second circuit means for producing a logic output signal indicating that the engine is operating at the selected engine speed; and

logic circuit means responsive to a logic output signal from both said third and fourth circuit means for producing a logic output signal indicating that the ignition spark is advanced;

to a logic output signal from both said third and fourth circuit means for producing a logic output signal indicating that the ignition spark is retarded and to a logic output signal from said third circuit means and a logic output signal from said fourth circuit means for producing a logic output signal indicating that the engine is properly timed.

7. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

circuit means responsive to said primary signals for producing a direct current engine RPM potential signal of a magnitude proportional to engine speed;

circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between sadi TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current engine RPM high reference potential signal and a direct current engine RPM low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said engine RPM potential signal at a selected engine speed;

first circuit means responsive to said engine RPM potential signal and said engine RPM high reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM high reference potential signal;

second circuit means responsive to said engine RPM potential signal and said engine RPM low reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM low reference potential signal;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

third circuit means responSive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

fourth circuit means responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, logic circuit means responsive to a logic output signal from both said first and second circuit means for producing a logic output signal upon a first output terminal thereof indicating that the engine is operating at a speed greater than a selected engine speed;

to a logic output signal from both said first and second circuit means for producing a logic output signal upon a second output terminal thereof indicating that the engine is operating at a speed less than the selected engine speed and to a logic output signal from said first circuit means and a logic output signal from said second circuit means for producing a logic output signal upon a third output terminal thereof indicating that the engine is operating at the selected engine speed; and

logic circuit means responsive to a logic output signal from both said third and fourth circuit means for producing a logic output signal upon a first output terminal thereof indicating that the ignition spark is advanced;

to a logic output signal from both said third and fourth circuit means for producing a logic output signal upon a second output terminal thereof indicating that the ignition spark is retarded and to a logic output signal from said third circuit means and a logic output signal from said fourth circuit means for producing a logic output signal upon a third output terminal thereof indicating that the engine is properly timed.

8. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

first circuit means responsive to said primary signals for producing a direct current engine RPM potential signal of a magnitude proportional to engine speed;

second circuit means responsive to said primary signals for producing an ignition signal when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current engine RPM high reference potential signal and a direct current engine RPM low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said engine RPM potential signal at a selected engine speed;

a first comparator circuit responsive to said engine RPM potential signal and said engine RPM high reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potEntial signal is less than the magnitude of said engine rpm high reference potential signal;

a second comparator circuit responsive to said engine RPM potential signal and said engine RPM low reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM low reference potential signal;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

a third comparator circuit responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

a fourth comparator circuit responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, logic circuit means responsive to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the engine is operating at a speed greater than a selected engine speed;

to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a second output terminal thereof indicating that the engine is operating at a speed less than the selected engine speed and to a logic output signal from said first comparator circuit and a logic output signal from said first comparator circuit for producing a logic output signal upon a third output terminal thereof indicating that the engine is operating at the selected engine speed; and

logic circuit means responsive to a logic output signal from both said third and fourth comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the ignition spark is advanced;

to a logic output signal from both said third and fourth comparator circuits for producing a logic output signal upon a second output terminal thereof indicating that the ignition spark is retarded and to a logic output signal from said third comparator circuit and a logic output signal from said fourth comparator circuit for producing a logic output signal upon a third output terminal thereof indicating that the engine is properly timed.

9. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

first circuit means responsive to said primary signals for producing a direct current engine RPM potential signal of a magnitude proportional to engine speed;

circuit means comprising a counter circuit and a NAND gate having an output terminal responsive to said primary signals for producing an ignition signal upon said output terminal of said NAND gate when an ignition spark potential is generated for the reference cylinder of said engine;

circuit means responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the periOd between said ignition and TDC signal when the ignition spark is advanced;

circuit means responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current engine RPM high reference potential signal and a direct current engine RPM low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said engine RPM potential signal at a selected engine speed;

a first comparator circuit responsive to said engine RPM potential signal and said engine RPM high reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM high reference potential signal;

a second comparator circuit responsive to said engine RPM potential signal and said engine RPM low reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM low reference potential signal;

means for producing a direct current timing angle high reference potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

a third comparator circuit responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

a fourth comparator circuit responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, logic circuit means responsive to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the engine is operating at a speed greater than a selected engine speed;

to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a second output terminal thereof indicating that the engine is operating at a speed less than the selected engine speed and to a logic output signal from said first comparator circuit and a logic output signal from said second comparator circuit for producing a logic output signal upon a third output terminal thereof indicating that the engine is operating at the selected engine speed; and

lgoic circuit means responsive to a logic output signal from both said third and fourth comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the ignition spark is advanced;

to a logic output signal from both said third and fourth comparator circuits for producing a logic ootput signal upon a second output terminal thereof indicating that the ignition spark is retarded and to a logic output signal from said third comparator circuit and a logic output signal from said fourth comparator circuit for producing a logic output signal upon a third output terminal thereof Indicating that the engine is properly timed.

10. An internal combustion engine ignition timing instrument comprising:

means for producing a primary signal each time an ignition spark is generated for said engine;

means for producing a TDC signal when the reference cylinder of said engine is at the top dead center position;

an integrator circuit responsive to said primary signals for producing a direct current engine RPM potential signal of a magnitude proportional to engine speed;

a counter circuit having an input terminal and output terminals, a NAND gate having a plurality of input terminals and an output terminal, means for applying said primary signals to said input terminal of said counter circuit and to one of said input terminals of said NAND gate and means for connecting each said output terminal of said counter circuit to a respective one input terminal of said NAND gate whereby said counter circuit and said NAND gate are responsive to said primary signals for producing an ignition signal upon said output terminal of said NAND gate when an ignition spark potential is generated for the reference cylinder of said engine;

first and second J-K flip-flops each having a clock input and a Q and Q output terminals, first and second NAND gates each having two input terminals and an output terminal, and third NAND gate having an input terminal and an output terminal, means for applying said ignition signals to said clock input terminal of one of said J-K flip-flops and said TDC signals to said clock input terminal of the other one of said J-K flip-flops and means for connecting said Q output terminal of one of said J-K flip-flops and said Q output terminal of the other one of said J-K flip-flops to respective and said input terminals of one of said first and second NAND gates and said Q output terminal of said other one of said J-K flip-flops and said Q output of said one of said J-K flip-flops to respective said input terminals of the other one of said first and second NAND gates and said output terminal of one of said first and second NAND gates to said input terminal of said third NAND gate whereby said J-K flip-flops and said NAND gates are responsive to said TDC and ignition signals for producing a series of timing angle signal pulses each of a width equal to the period between said TDC and ignition signals when the ignition spark is retarded and to the period between said ignition and TDC signals when the ignition spark is advanced;

an averager circuit responsive to said timing angle signal pulses for producing a direct current timing angle potential signal of a selected one polarity when the ignition spark is retarded and of the opposite polarity when the ignition spark is advanced and of a magnitude proportional to the number of degrees of ignition spark retard or advance;

means for producing a direct current engine RPM high reference potential signal and a direct current engine RPM low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said engine RPM potential signal at a selected engine speed;

a first comparator circuit responsive to said engine RPM potential signal and said engine RPM high reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM high reference potential signal;

a second comparator circuit responsive to said engine RPM potential signal and said engine RPM low reference potential signal for producing a logic output signal when the magnitude of said engine RPM potential signal is greater than and a logic output signal when the magnitude of said engine RPM potential signal is less than the magnitude of said engine RPM low reference potential signal;

means for producing a direct current timing angle high reFerence potential signal and a direct current timing angle low reference potential signal of selected respective magnitudes greater than and less than the magnitude of said timing angle potential signal at a selected number of degrees of ignition spark retard or advance;

a third comparator circuit responsive to said timing angle potential signal and said timing angle high reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle high reference potential signal;

a fourth comparator circuit responsive to said timing angle potential signal and said timing angle low reference potential signal for producing a logic output signal when the magnitude of said timing angle potential signal is greater than and a logic output signal when the magnitude of said timing angle potential signal is less than the magnitude of said timing angle low reference potential signal, logic circuit means responsive to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the engine is operating at a speed greater than a selected engine speed;

to a logic output signal from both said first and second comparator circuits for producing a logic output signal upon a second output terminal thereof indicating that the engine is operating at a speed less than the selected engine speed and to a logic output signal from said first comparator circuit and a logic output signal from said second comparator circuit for producing a logic output signal upon a third output terminal thereof indicating that the engine is operating at the selected engine speed; and

logic circuit means responsive to a logic output signal from both said third and fourth comparator circuits for producing a logic output signal upon a first output terminal thereof indicating that the ignition spark is advanced;

to a logic output signal from both said third and fourth comparator circuits for producing a logic output signal upon a second output terminal thereof indicating that the ignition spark is retarded and to a logic output signal from said third comparator circuit and a logic output signal from said fourth comparator circuit for producing a logic output signal upon a third output terminal thereof indicating that the engine is properly timed.