SFI SYSTEM

Electronic Spark Advance (ESA)

1. The optimum ignition timing is selected according to signals from the sensors and the ignition signal (IGt) is sent to the igniter.

   

2. The ignition timing can be expressed using the following equation. The ignition timing is set initially to 10° BTDC.

   Ignition Timing = A. Initial Set Ignition Timing or B. Basic Advanced Angle + C. Corrected Advanced Angle

   A. Fixed Advanced Angle Characteristics	Fixed to 5° BTDC when starting the engine. The service terminals are short-circuited, and it is fixed to 10° BTDC when the throttle is closed.
   B. Basic Advanced Angle Characteristics	Selects the optimum ignition timing, depending on each sensor signal.
   C. Correction Advanced Angle Characteristics	Selects the appropriate advanced or retarded angles according to the engine status at that time, depending on each sensor signal.
   C-1. Warm-up Advanced Angle Characteristics	Sets the ignition timing to advanced angle according to the operating status to improve drivability, when the coolant temperature is low.
   C-2. Idling Stability Advanced Angle Characteristics	Sets the ignition timing to advance to stabilize idle speed when the idle speed is low. Also, as the speed gets higher, the ignition timing is retarded.
   C-3. Knocking Correction Retarded Angle	When knocking is generated, the ignition timing is corrected according to a signal from the knock control sensor.

3. If engine knocking is detected, the ignition timing is retarded gradually in equal steps according to the size of knocking, until the engine stops knocking.

4. After knocking has stopped, the ignition timing is advanced gradually in equal steps. If the engine knocks again during this process, then the ignition timing is retarded again.

   Figure 1. Knocking Feedback Control Cycle

   

   *1	Knocking Occurs
   *2	Retard
   *3	Advance
   *4	No Knocking

Electronic Throttle Control System-intelligent (ETCS-i)

1. By controlling the engine output optimally for the accelerator pedal opening angle with centralized control using the ECM, good accelerator controllability and vehicle stability are enabled across all speed ranges.

2. Ordinary throttle valve opening angle control (non-linear control) and the idle speed control (ISC) functions have been brought together in the throttle body with motor assembly.

3. By integrated control with the powertrain, superior operability is ensured and comfort is improved.

4. To enable driving in the event of trouble, the system is duplicated to ensure reliability.

   

   ETCS-i Control

   Driving Control	Controls the opening angle of the throttle valve in order to produce engine output in response to the driving conditions and the accelerator pedal opening angle.
   TRC/VSC Cooperative Control*	Stabilizes the vehicle by communicating with the skid control ECU when the TRC and VSC are operating.
   Idle Speed Control	Controls the fast idle speed to suit the engine coolant temperature and the idle speed after the engine is warmed up. In addition, it controls the idle speed in accordance with the fuel injection volume and throttle position.

   *: Models with brake control system (ABS with EBD, Brake Assist, TRC and VSC)

Dual Variable Valve Timing-intelligent (VVT-iE and VVT-i)

1. By adopting dual Variable Valve Timing-intelligent (VVT-iE and VVT-i) which can vary the camshaft phase to affect intake and exhaust succession, thus providing high output power with improved fuel efficiency and reduced emissions.

2. Intake valve timing control is by Variable Valve Timing-intelligent by Electric motor (VVT-iE), performed via the cam timing control motor with EDU assembly and camshaft timing gear assembly. Valve timing control via VVT-iE is performed using an electrically driven cam timing control motor with EDU assembly, and so valve timing control does not rely on oil pressure and is performed from the time of engine start.

3. VVT-iE has a wide operating range, and can improve startability of a cold engine by varying intake valve timing toward the advanced side, and shift valve timing towards the retarded side in a warmed-up engine to prevent preignition. Also, when driving at low load, the timing can be set to most retarded to improve fuel efficiency according to the Atkinson cycle.

4. Exhaust valve timing is by Variable Valve Timing-intelligent (VVT-i), performed via the camshaft timing oil control valve assembly and camshaft timing exhaust gear assembly.

5. The ECM, in order to achieve the most suitable valve timing control for the current driving conditions, detects the phase shifts of each camshaft and performs feedback control via the cam position sensor (No. 1 crank position sensor).

   

6. The VVT-iE and VVT-i systems deliver excellent benefits in vehicle states such as those shown in the illustration below.

   

   

Cooling Fan Control

1. According to the cooling fan drive request signal (low or high) from the air conditioning amplifier assembly and the engine coolant temperature, the ECM regulates the cooling fan speed over 2 levels. A cooling fan drive request signal is determined by the air conditioning amplifier assembly depending on mainly the refrigerant pressure and the A/C switch status.

2. The low speed operation is accomplished by applying the current through a resistor, which reduces the speed of the cooling fan.

   

   Cooling Fan Operation

   Engine Coolant Temperature	Cooling Fan Drive Request Signal	Cooling Fan Operation
   Low	Off	Off
   	Low	Low
   	High	High
   High	Off	High
   	Low	High
   	High	High

Fuel Pump Control

1. In this vehicle, there are 2 types of fuel pump controls. The fuel pump is controlled to an optimum speed to match the engine operating conditions, and the fuel pump operation is stopped when the SRS airbags deploy.

2. The ECM transmits a fuel pump operation request signal to the fuel pump control ECU that corresponds to the engine operating conditions. The fuel pump control ECU receives this request signal and controls the speed of the fuel pump. As a result, under light engine loads, fuel pump speed is kept low to reduce electric power loss.

3. A fuel cut control is used to stop the fuel pump when the SRS airbags deploy. In this control, if an airbag deployment signal from the airbag sensor assembly is detected by the ECM, the ECM will turn off the EFI MAIN relay. As a result, the power supply to the fuel pump control ECU is stopped, causing the fuel pump to stop operating.

4. The fuel pump control ECU controls fuel pump speed by receiving a duty cycle signal (FPC terminal input) from the ECM.

   

Crankshaft Position Sensor and Camshaft Position Sensor

1. Magneto Resistive Element (MRE) type sensors are used for the crank position, intake cam position and exhaust cam position sensors (No. 1 crank position sensors).

2. The timing rotor of the crankshaft has 34 teeth, with 2 teeth missing. Based on these teeth, the crank position sensor transmits crank position signals (NE signal) consisting of 33 high or low output pulses every 10° per revolution of the crankshaft. The ECM uses the NE signal for detecting the crank position as well as for detecting the engine speed. It uses the missing teeth signal for determining the top dead center.

3. To detect the cam position, a timing rotor on the intake and a timing rotor on the exhaust camshaft are used to generate 3 (3 high output, 3 low output) pulses for every 2 revolutions of the crankshaft.

   

   *1	Crank Position Sensor	*2	Timing Sprocket
   *3	Exhaust Cam Position Sensor (No. 1 Crank Position Sensor)	*4	Intake Cam Position Sensor (No. 1 Crank Position Sensor)
   *5	Timing Rotor	-	-

   Figure 2. Sensor Output Waveforms

   

   *1	Crank Position Sensor
   *2	Intake Cam Position Sensor (No. 1 Crank Position Sensor)
   *3	Exhaust Cam Position Sensor (No. 1 Crank Position Sensor)

4. An MRE type sensor consists of an MRE, a magnet and a sensor. The direction of the magnetic field changes due to the profile (protruding and non-protruding portions) of the timing rotor, which passes by the sensor. As a result, the resistance of the MRE changes, and the output voltage to the ECM changes to either high or low. The ECM detects cam position based on this output voltage.

5. The differences between the MRE type sensor and the pick-up coil type sensor used on a conventional model are as follows.

   
   

   • An MRE type sensor outputs a constant level of Hi/Lo digital signals regardless of the engine speed. Therefore, an MRE type sensor can detect the positions of the crankshaft and camshaft at an early stage of cranking.

   
   

   • A pick-up coil type sensor outputs analog signals with levels that change with engine speed.

   

6. In order to deliver a smooth engine restart from the engine stop state, the MRE type crank position sensor provided on models with the stop and start system detects crankshaft movements swinging back and forth from the timing rotor rotation direction when the engine has been brought into a stop, helping the ECM determine a more exact crankshaft stop position.

7. The MRE type crank position sensor determines the timing rotor rotation direction from the phase difference between the 2 rectangular wave signals generated by the sensor itself, and then transmits Hi/Lo signals, a short low voltage time when the timing rotor rotates in the normal direction and a long low voltage time when in the reverse direction, to the ECM.

   Figure 3. Sensor Output Waveforms

   

   *1	Normal Rotation Direction
   *2	Ne Signal
   *3	Reverse Rotation Direction

Accelerator Pedal Sensor

1. A non-contact type accelerator pedal sensor assembly is used.

2. This sensor uses a Hall IC*1, which can retrieve the strength of the magnetic field as an electrical signal, using the Hall effect*2, in which the output voltage can be directly received in accordance with the accelerator pedal depression amount. When the accelerator pedal depression amount changes, the angle of the magnetic field towards the flow of the current in the Hall IC changes. As a result, the strength of the current and vertical magnetic field changes. Due to this, the change in the voltage generated in the vertical direction towards the forced current and direction of the magnetic field is sent to the ECM as an accelerator pedal depression amount signal. Also, in order to ensure reliability, duplicate sensors (main and sub) with differing sensor output characteristics, are used.

   Tech Tips

   *1: An electrical component which uses the electromotive force resulting from the potential difference in the magnetic field.

   *2: Phenomenon in which a potential difference occurs in the electric current and magnetic field in the vertical direction when a magnetic field in the vertical direction is applied and electric current is flowing through a rod or plated conductor or semiconductor.

   

Throttle Position Sensor

1. A non-contact type throttle position sensor is used.

2. This sensor uses a Hall IC*1, which can retrieve the strength of the magnetic field as an electrical signal using Hall effect*2, in which the output voltage can be directly received in accordance with the throttle valve opening angle. When the throttle valve opening angle changes, the angle of the magnetic field towards the flow of the current in the Hall IC changes. As a result, the strength of the current and vertical magnetic field changes. Due to this, the change in the voltage generated in the vertical direction towards the current and direction of the magnetic field is sent to the ECM as a throttle valve opening angle signal. Also, duplicate sensors (main and sub) with differing sensor output characteristics, are used, ensuring reliability.

   Tech Tips

   *1: An electrical component which uses the electromotive force resulting from the potential difference in the magnetic field.

   *2: Phenomenon in which a potential difference occurs in the electric current and magnetic field in the vertical direction when a magnetic field in the vertical direction is applied and electric current is flowing through a rod or plated conductor or semiconductor.

   Figure 4. Sensor Output Characteristics

   

   *1	Output Voltage
   *2	Fully Closed
   *3	Fully Open
   *4	Throttle Valve Opening Angle

Throttle Body

1. A single valve type electronic control throttle body with motor assembly that drives the throttle valve by a motor to ensure excellent driving stability.

2. A DC motor with good response and low power consumption is adopted for the motor for throttle valve drive.

3. Driver operations (the amount of the accelerator pedal being depressed) are transmitted to the ECM by the accelerator pedal sensor assembly provided on the accelerator pedal. The ECM determines the throttle valve opening angle that matches the driving status to drive the throttle control motor. The throttle valve opening angle is fed back to the ECM by the throttle position sensor.

4. When an error is detected, the driver is notified by a warning light in the combination meter assembly and current to the motor is cut. This causes the throttle valve to return to its predetermined angle by the throttle valve return spring. Fuel cut and ignition retard adjust the engine output according to the accelerator pedal opening angle to allow the vehicle to continue at a minimal speed.

   

   *1	Throttle Control Motor	*2	Throttle Valve
   *3	Return Spring	-	-
   *a	Throttle Position Sensor Portion	-	-

Camshaft Control Motor

1. The cam timing control motor with EDU assembly consists of a motor that operates the camshaft timing gear assembly in the advance or retard direction, an Electronic Driver Unit (EDU) that controls the rotation of the motor, and a Hall IC type rotation sensor that detects the rotation of the motor.

2. The motor is a brushless type DC motor that is installed in the timing chain cover assembly forward of the camshaft timing gear assembly. It rotates coaxially with the intake camshaft.

3. In accordance with the target valve timing, the ECM transmits the motor speed and direction of rotation instruction signals to the EDU. Based on those signals, the EDU drives the motor to advance or retard the timing of the intake camshaft.

4. The EDU always monitors the operation of the motor, and transmits the actual motor speed, direction of rotation, and the state of operation signals to the ECM. The ECM uses these signals to diagnose malfunctions.

   

   *a	Timing Chain Cover Fixed Surface	*b	Camshaft Timing Gear Assembly Fitting Portion
   *c	Motor Driver (EDU) Portion	*d	Brushless Type DC Motor Portion

   Figure 5. Circuit Diagram

   

Camshaft Timing Oil Control Valve

1. The camshaft timing oil control valve assembly controls the spool valve using duty cycle control from the ECM. This allows engine oil pressure to be applied to the camshaft timing exhaust gear assembly advance or retard side. When the engine is stopped, the camshaft timing oil control valve assembly is in the most advanced position.

   

   *a	To Camshaft Timing Exhaust Gear Assembly (Retard Side)	*b	To Camshaft Timing Exhaust Gear Assembly (Advance Side)
   *c	Drain	*d	Oil Pressure

Water Temperature Sensor

1. This sensor detects the engine coolant temperature. A thermistor whose resistance value greatly changes according to the temperature is built-in. Changes in the coolant temperature are detected by the changes in the thermistor resistance value.

   

   *1	Resistance
   *2	Thermistor
   *3	Coolant Temperature

Oxygen Sensor and Air Fuel Ratio Sensor

1. The oxygen sensor and the air fuel ratio sensor differ in output characteristics.

2. The output voltage of the oxygen sensor changes in accordance with the oxygen concentration in the exhaust gas. The ECM uses this output voltage to determine whether the present air fuel ratio is richer or leaner than the stoichiometric air fuel ratio.

3. Approximately 0.4 V is constantly applied to the air fuel ratio sensor, which outputs an amperage that varies in accordance with the oxygen concentration in the exhaust gas. The ECM converts the changes in the output amperage into voltage in order to linearly detect the present air fuel ratio.

   

4. The basic construction of the oxygen sensor and the air fuel ratio sensor is the same. However, they are divided into the cup type and the planar type, according to the different types of heater construction that are used.

5. The cup type sensor contains a sensor element that surrounds a heater.

6. The planar type sensor uses alumina, which excels in heat conductivity and insulation, to integrate a sensor element with a heater, thus improving the warm up performance of the sensor.

   

   *1	Air Fuel Ratio Sensor (Planar Type)	*2	Oxygen Sensor (Cup Type)
   *3	Diffusion Resistance Layer	*4	Atmosphere
   *5	Heater	*6	Platinum Electrode
   *7	Alumina	*8	Sensor Element (Zirconia)

Knock Control Sensor

1. In a conventional knock control sensor (resonant type), a vibration plate is built into the sensor. This plate has the same resonance point as the knocking frequency of the engine block. This sensor can only detect vibration in this frequency band.

2. A flat type knock control sensor (non-resonant type) has the ability to detect vibration in a wider frequency band (from about 5 kHz to 15 kHz). It has the following features.

3. The engine knocking frequency will vary slightly depending on the engine speed. The flat type knock control sensor can detect vibration even when the engine knocking frequency changes. Due to the use of the flat type knock control sensor, the vibration detection ability is increased compared to a conventional type knock control sensor, and more precise ignition timing control is possible.

   Figure 6. Characteristics of Knock Control Sensor

   

4. A flat type knock control sensor is installed to an engine by placing it over the stud bolt installed on the cylinder block sub-assembly. For this reason, a hole for the stud bolt exists in the center of the sensor.

5. In the sensor, a steel weight is located in the upper portion. An insulator is located between the weight and a piezoelectric element.

6. An open/short circuit detection resistor is integrated in the sensor. When the ignition is ON, the open/short circuit detection resistor in the knock control sensor and the resistor in the ECM keep the voltage at terminal KNK1 constant. An Integrated Circuit (IC) in the ECM constantly monitors the voltage of terminal KNK1. If the open/short circuit occurs between the knock control sensor and the ECM, the voltage of terminal KNK1 will change and the ECM will detect the open/short circuit and store a Diagnostic Trouble Code (DTC).

   

   *1	Steel Weight	*2	Insulator
   *3	Piezoelectric Element	*4	Open/Short Circuit Detection Resistor
   *5	Vibration Plate	-	-
   *a	Flat Type Knock Control Sensor (Non-resonant Type)	*b	Conventional Type Knock Control Sensor (Resonant Type)

   

   *1	Flat Type Knock Control Sensor
   *2	Open/Short Circuit Detection Resistor
   *3	Piezoelectric Element

7. Vibrations caused by knocking are transmitted to the steel weight. The inertia of this weight applies pressure to the piezoelectric element. This action generates electromotive force.

   

   *1	Steel Weight	*2	Piezoelectric Element
   	Inertia	-	-

Ignition Coil

1. An igniter is integrated with the ignition coils, which are provided independently in each cylinder. This improves ignition timing accuracy, reduces high-voltage loss and enhances the overall reliability of the ignition system by eliminating the distributor.

2. The spark plug caps, which provide contact to spark plugs, are integrated with a No. 1 ignition coil. Also, an igniter is enclosed to simplify the system.

   

   *1	Igniter	*2	Iron Core
   *3	Spark Plug Cap	*4	Secondary Coil
   *5	Primary Coil	-	-

Spark Plug

1. Long-reach type, narrow-diameter spark plugs with iridium central electrodes are used.

2. By using needle-needle type electrodes, ignitability is improved, and with their heat index of 16, they are effective against carbon fouling.

3. Because iridium offers an extremely high level of wear resistance, the central electrode could be made thinner, and more reliable ignition is achieved. In addition, the improved wear resistance of the center electrode offers longer operational life and so improves maintainability.

4. By narrowing the diameter of the threaded portion of the spark plug and changing to a long-reach type, the water jacket around the spark plug was optimized and the cooling ability of the cylinder head sub-assembly was improved.

   Tech Tips

   Because the plug size differs from that of normal spark plugs, be careful not to use the wrong tools during installation/removal procedures.

   

   *a	Conventional Type	*b	Long-reach Narrow-diameter Type
   *c	Long-reach	*d	Narrow-diameter Portion
   *e	Iridium Tip	*f	Platinum Tip