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Internal Combustion Motor Modes of Operation

Internal Combustion Motor Modes of Operation. Super-Mileage Fuel Injection Team SDP05. The Combustion Process. Four Cycles -Intake -Compression -Combustion -Exhaust We know this part, but what about modes of operation?. What modes are we interested in?.

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Internal Combustion Motor Modes of Operation

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  1. Internal Combustion Motor Modes of Operation Super-Mileage Fuel Injection Team SDP05

  2. The Combustion Process • Four Cycles -Intake -Compression -Combustion -Exhaust • We know this part, but what about modes of operation?

  3. What modes are we interested in? • The two main modes of interest are the start sequence and the standalone operation of the motor. • The operating mode is a boolean function of some key control inputs to the system. • The key inputs are the ignition, accessory, and starter control.

  4. The Ignition Key Cylinderof Your Car The Control States of the Key Cylinder have a Hierarchal structure. Everything is off in the OFF State. However, each following step keeps the control inputs before it asserted.

  5. But What Do These Things Do? • ACC -> Accessory Power On -This is like a switch that applies power to the “peripherals” of your car. -Peripherals include windows, stereos, lighters, air conditioning, etc. -The most important peripheral for us is the fuel pump.

  6. START -> Starter • The Starter is an extremely powerful electric motor. • The starter motor is what begins the combustion process. • It must be capable of overcoming all of the mechanical friction forces of the system so that stable 4-cycle operation can be achieved. • The START control bit also lets the computer know that the car is starting cold and that it should adjust the fuel mixture accordingly (This often means a richer mixture).

  7. ON -> Ignition • The Ignition Control Bit powers up the ignition system and the ECU (Engine Control Unit), the computer that controls the air/fuel ratio. • The Ignition system pulses the spark plug at the appropriate time in the combustion cycle and the ECU controls the A/F mixture in the cylinder (a fraction of the ECU capabilities of a real automobile is the main part of our project).

  8. The Start Sequence • The Start Sequence is important to us because our customer finds the best fuel efficiency in running for short bursts and then shutting down the motor. • It is crucial that our start sequence be extremely efficient.

  9. Steps in the Start Sequence • Turn the key to Start: Bear in mind that ACC and ON remain in the high state. This ensures that the A/F computer and fuel pump are on. • Even in the Start state, the A/F computer performs calculations. It is essentially the same as normal motor operation without the inertia of the mechanical system to continue the cycle. • Sometimes computers are coded to alter the fuel mixture for the start sequence.

  10. Steps in the Start Sequence (II) • ON – After a combustion cycle or two of the motor, enough mechanical inertia should be developed as to negate the need for the starter motor to drive the system. • When that happens, the key is released and falls back to its ON state during which the computer continues A/F calculations OR in the case that the start mixture was hard coded, returns to its own determination of the proper mixture.

  11. Any Questions?

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