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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

Internal Combustion Motor Modes of Operation

Super-Mileage Fuel Injection Team


the combustion process
The Combustion Process
  • Four Cycles





  • We know this part, but what about modes of operation?
what modes are we interested in
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.
the ignition key cylinder of your car
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.

but what do these things do
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.

start starter
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).
on ignition
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).
the start sequence
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.
steps in the start sequence
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.
steps in the start sequence ii
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.