SFI SYSTEM DETAILS

Dual VVT-i System

1. The Dual VVT-i system is designed to control the intake and exhaust camshafts within a range of 40° and 35° respectively (of crankshaft angle) to provide valve timing that is optimally suited to the engine condition. This improves torque in all the speed ranges as well as increasing fuel economy and reducing exhaust emissions.

2. For the intake valves, the VVT-iE uses electric motors to control the valve timing. Because the VVT-iE is actuated by electric motors, it can affect optimal valve timing control even when the engine oil pressure is low, such as when the engine oil temperature or the engine speed is low. Because this system can control the valve timing from the time the engine is started, it can set the most retarded timing position to be more retarded than the starting valve timing.

3. The exhaust side is VVT-i that uses engine oil pressure to control the valve timing.

   

   Text in Illustration

   *1	Intake Mass Air Flow Meter Sub-assembly (Bank 1, Bank 2)	*2	Throttle Position Sensor
   *3	Vehicle Speed Signal	*4	Camshaft Control Motor (Bank 2)
   *5	Camshaft Timing Oil Control Valve (Bank 2)	*6	Camshaft Position Sensor
   *7	Exhaust VVT Sensor (Bank 2)	*8	Intake VVT Sensor (Bank 2)
   *9	Engine Coolant Temperature Sensor	*10	Intake VVT Sensor (Bank 1)
   *11	Exhaust VVT Sensor (Bank 1)	*12	Crankshaft Position Sensor
   *13	Camshaft Timing Oil Control Valve (Bank 1)	*14	Camshaft Control Motor (Bank 1)
   *15	ECM	-	-

   

4. The Dual VVT-i system delivers excellent benefits in the different operating condition as follows:

   
   

   • During Idling

     

     Objective	Effect
     Eliminating overlap to reduce blowback to the intake side.	Stabilized idling speed Better fuel economy

   • In Low Speed Range with Light to Medium Load

     

     Objective	Effect
     Retarding the intake valve close timing and reducing pumping loss, increasing overlap and increasing internal EGR.	Better fuel economy Improved emission control

   • In Low to Medium Speed Range with Heavy Load

     

     Objective	Effect
     Advancing the intake valve close timing, reducing intake air blowback to the intake side and improving volumetric efficiency.	Improved torque in low to medium speed range

   • In High Speed Range with Heavy Load

     

     Objective	Effect
     Retarding the intake valve close timing and improving volumetric efficiency using the inertia force of the intake air.	Improved output

   • At Low Temperatures

     

     Objective	Effect
     Eliminating overlap to reduce blow back to the intake side, adjusting valve timing at extremely low temperatures and increasing the control range as the temperature rises.	Stabilized fast idle speed Better fuel economy

   • Upon Starting

   • Stopping Engine

     

     Objective	Effect
     Controlling valve timing and adjusting it to the optimal timing for engine start.	Improved startability

Electronic Throttle Control System-intelligent (ETCS-i)

1. In the conventional throttle body, the throttle valve angle is determined invariably by the amount of the accelerator pedal effort. In contrast, ETCS-i uses the ECM to calculate the optimal throttle valve angle that is appropriate for the respective driving condition and uses a throttle control motor to control the angle.

2. In case of an abnormal condition, this system switches to the limp mode.

   

Fuel Pressure Sensor

1. The fuel pressure sensor, which is mounted on the delivery pipe, outputs a signal to the ECM that represents the fuel pressure in the delivery pipe in order to allow the constant regulation of the fuel at an optimal pressure.

   

Crankshaft Position, Camshaft Position and VVT Sensors

1. The Magnetic Resistance Element (MRE) sensors are used for the crankshaft position, camshaft position, and VVT sensors.

2. The timing rotor for the crankshaft position sensor is installed on the back end of the crankshaft. The timing rotor has 34 teeth, with 2 teeth missing, at 10° intervals. Based on these teeth, the crankshaft position sensor transmits crankshaft position signals (NE signal) consisting of 33 high and low output pulses every 10° per revolution of the crankshaft, and 1 high and low output pulse every 30°. The ECM uses the NE signal for detecting the crankshaft position as well as for detecting the engine speed. The ECM uses the missing teeth signal for determining the top dead center.

3. The camshaft position sensor uses a timing rotor that is installed on the front end of the intake camshaft sprocket of the right bank. Based on the timing rotor, the sensor outputs camshaft position signals (G2 signal) consisting of 6 (3 high output, 3 low output) pulses for every 2 revolutions of the crankshaft. The ECM compares the G2 and NE signals to detect the camshaft position and to identify the cylinder.

4. The intake and exhaust VVT sensors use timing rotors that are installed on the intake and exhaust camshafts of each bank. Based on the timing rotors, the sensors output VVT position signals consisting of 6 (3 high output, 3 low output) pulses for every 2 revolutions of the crankshaft. The ECM compares these VVT position signals to with NE signal to detect the actual valve timing.

   

   Text in Illustration

   *1	Camshaft Position Sensor	*2	Timing Rotor
   *3	Intake VVT Sensor (Bank 1)	*4	Exhaust VVT Sensor (Bank 1)
   *5	Crankshaft Position Sensor	-	-

   

5. The MRE type sensor consists of an MRE, a magnet and a sensor.

6. 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 high or low. The ECM detects the crankshaft and camshaft positions based on this output voltage.

7. The differences between the MRE type sensor and the pick-up coil type sensor used on the conventional models are as follows:

   
   

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

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

   

Accelerator Pedal Sensor Assembly

1. This non-contact type accelerator pedal position sensor uses a Hall IC which is mounted on the accelerator pedal arm.

2. A magnetic yoke is mounted at the base of the accelerator pedal arm. This yoke rotates around the Hall IC in accordance with the amount of effort that is applied to the accelerator pedal. The Hall IC converts the changes in the magnetic flux that occur into electrical signals, and outputs them in the form of accelerator pedal position signals to the ECM.

3. This accelerator pedal position sensor includes 2 Hall ICs and circuits for the main and sub signals. It converts the accelerator pedal depressed angles into electric signals with two differing characteristics and outputs them to the ECM.

   

Throttle Position Sensor

1. A non-contact type throttle position sensor is used. This sensor uses a Hall IC which is mounted on the throttle body.

2. The Hall IC is surrounded by a magnetic yoke. The Hall IC converts the changes that occur in the magnetic flux into electrical signals and outputs them as throttle valve effort to the ECM.

3. The Hall IC contains circuits for the main and sub signals. It converts the throttle valve opening angles into electric signals with two differing characteristics and outputs them to the ECM.

   

Air Fuel Ratio Sensor and Oxygen Sensor

1. A planar type air fuel ratio sensor and a cup type oxygen sensor are used. 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 in accordance with the different types of heater construction used.

2. The planar type air fuel ratio sensor uses alumina, which excels in heat conductivity and electrical insulation, to integrate the sensor element with a heater, thus improving the warmup performance of the sensor.

3. The cup type oxygen sensor contains a sensor element that surrounds the heater.

   

   Text in Illustration

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

4. As illustrated below, the conventional oxygen sensor is characterized by a sudden change in its output voltage at the threshold of the stoichiometric air fuel ratio (14.7:1). In contrast, the air fuel ratio sensor data is approximately proportionate to the existing air fuel ratio. The air fuel ratio sensor converts the oxygen density to current and sends it to the ECM. As a result, the detection precision of the air fuel ratio has been improved. The air fuel ratio sensor data can be viewed using a Global TechStream (GTS).

   

Camshaft Timing Oil Control Valve

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

   

   Text in Illustration

   *1	Sleeve	*2	Spring
   *3	Spool Valve	-	-
   *a	To VVT-i Controller (Advance Side)	*b	To VVT-i Controller (Retard Side)
   *c	Drain	*d	Oil Pressure

Camshaft Control Actuator

1. The camshaft control actuator rotates the intake camshaft to the advance side or retard side, and consists of a 2-stage cycloid reduction unit which reduces the rotation speed of the camshaft control motor.

2. The rotation of the camshaft control motor rotates the planetary gear via the cycloid reduction unit. By rotating the planetary gear, the intake camshaft fixed into the camshaft gear is rotated to the advance side or retard side.

   

   Text in Illustration

   *1	Camshaft Control Motor	*2	Boss Weight
   *3	Signal Rotor	*4	Cycloid Reduction Unit
   *5	Sprocket Gear	*6	Bearing
   *7	Eccentric Shaft	*8	Large Gear
   *9	Planetary Gear	*10	Small Gear
   *11	Camshaft Gear	*12	Housing
   *13	Sprocket	*14	Intake Camshaft

3. The cycloid reduction unit consists of a sprocket gear, an eccentric shaft, a planetary gear and a camshaft gear.

4. The eccentric shaft has a circular shape, which is eccentric in relation to the rotation axis of the camshaft, and connects with the sprocket gear.

5. The sprocket gear has 1 tooth more than the large gear of the planetary gear, and the small gear of the planetary gear has 1 tooth less than the camshaft gear.

6. Through the eccentric movement of the eccentric shaft, the planetary gear rotates while meshing with the sprocket gear and camshaft gear.

7. When the eccentric shaft rotates once, the planetary gear moves while meshing with the sprocket gear, and rotates by 1 tooth only. The rotations that are decelerated by the cycloid reduction unit cause the intake camshaft to rotate.

   

Camshaft Control Motor

1. The camshaft control motor consists of a motor that operates the camshaft control actuator in the advance or retard direction, an EDU that controls the rotational condition of the motor and a Hall IC type rotational sensor that detects the rotational condition of the motor.

2. The motor is a brushless type DC motor that is installed in the engine front cover in front of the camshaft control actuator. The motor rotates coaxially with the intake camshaft.

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

4. The EDU always monitors the motor operating condition and transmits the actual motor rotational speed signals, the actual motor rotational direction signals and the operating state signals to the ECM. The ECM uses these signals to diagnose malfunctions.

   

Ignition Coil Assembly

1. The DIS provides 8 ignition coil assemblies, one for each cylinder. The spark plug caps, which provide contact to spark plugs, are integrated with the ignition coil. Also, the ignition are enclosed to simplify the system.

   

   Text in Illustration

   *1	Igniter	*2	Iron Core
   *3	Plug Cap	*4	Secondary Coil
   *5	Primary Coil	-	-
   *a	Ignition Coil Cross Section	-	-

Spark Plug

1. Long-reach type spark plugs are used. This type of spark plug allows the area of the cylinder head which receives the spark plugs to be made thick. Thus, the water jacket can be extended near the combustion chamber, which contributes to cooling performance.

2. The triple ground electrode type iridium-tipped spark plugs are used to achieve a 193000 km (120000 miles) maintenance interval. By making the center electrode if iridium, it is possible to plugs. Furthermore, 2 ground electrodes have been added to further improve ignitability, wear resistance, and fouling resistance.

   

   Text in Illustration

   *1	Iridium Tip	*2	Platinum Tip
   *a	Long-reach	*b	Cylinder Head Cross Section
   	Water Jacket	-	-

ACIS

1. While the engine is running at low-to-medium speed under heavy load, the ECM causes the actuator to close the control valve. As a result, the effective length of the intake manifold is lengthened and the intake efficiency in the low-to-medium speed range is improved due to the dynamic effect (inertia) of the intake air, thereby increasing power output.

   

2. Under any condition except when the engine is running at low-to-medium speed under heavy load, the ECM causes the actuator to open the control valve. When the control valve is open, the effective length of the intake air chamber is shortened and peak intake efficiency is shifted to the low-to-high engine speed range, thus providing greater output at low-to-high engine speeds.

   

ETCS-i

1. The ECM drives the throttle control motor by determining the target throttle valve opening in accordance with the respective operating condition as follows:

2. Controls the throttle to an optimal throttle valve angle that is appropriate for the driving condition such as the amount of the accelerator pedal effort and the engine speed in order to realize excellent throttle control and comfort in all operating ranges.

   

3. In situations in which low-μ (low friction) road surface conditions can be anticipated, such as when driving in the snow, the rate of throttle valve opening can be controlled to help vehicle stability while driving on the slippery surface. This is accomplished by turning on SNOW mode. Pressing the SNOW side of the pattern select switch activates this mode. This mode modifies the relationship and reaction of the throttle to the accelerator pedal, and assists the driver by reducing the engine output from that of a normal level.

4. The ECM controls the throttle valve in order to constantly maintain an ideal idle speed.

5. The ECM effects cooperative control with the TCM in order to control the throttle valve at a position that is optimal for the driving conditions. Thus, it ensures a quick response to the driver's accelerator pedal effort and reduces shift shocks.

6. As part of the TRC function, the throttle valve is closed by a demand signal from the skid control ECU if an excessive amount of slippage is created at a driving wheel, thus facilitating the vehicle in ensuring excellent vehicle stability and driving force.

7. In order to bring the effectiveness of the VSC function control into full play, the throttle valve angle is controlled by effecting a coordination control with the skid control ECU.

8. An ECM with an integrated cruise control ECU directly actuates the throttle valve for operation of the cruise control.

9. The dynamic radar cruise control uses a millimeter wave radar sensor and the driving support ECU to determine the distance of the vehicle driven ahead, its direction, and relative speed. Thus, the system can effect deceleration cruising control, follow up cruising control, cruising at a fixed speed control, and acceleration cruising control. To make these controls possible, the ECM controls the throttle valve. (Models with dynamic radar cruise control system)

Fuel Pump Control

1. A fuel cut function is used to stop the fuel pump once when any of the SRS airbags have deployed. In this system, the airbag deployment signal from the airbag sensor assembly is detected by the ECM, and the ECM turns off the circuit opening relay. After the fuel cut function has been activated, turning the power source from off to on (IG) cancels the fuel cut function, and the engine can be restarted.

2. The ECM uses the fuel pump relay and the fuel pump resistor to control the fuel pump speed in accordance with driving conditions.

   

Cooling Fan Control System

1. A cooling fan control system is used. To achieve an optimal fan speed in accordance with the engine coolant temperature, engine speed, vehicle speed, and air conditioning operating conditions, the ECM calculates an appropriate fan speed and sends signals to the cooling fan ECU via the main body ECU and the front controller. Upon receiving the signals from the ECM, the cooling fan ECU actuates the fan motors.

   

2. The ECM controls the cooling fan speed in accordance with the value of the engine coolant temperature as shown in the graph below. When the engine coolant temperature is higher than a specific value, the control differs depending on whether the engine speed is above idling speed, or is at idling speed or below.

   

3. The ECM controls the cooling fan speed in accordance with the value of the air conditioning refrigerant pressure as shown in the graph below. When the air conditioning refrigerant pressure is higher than a specific value, the control differs depending on whether the engine speed is above a low speed, or is at a low speed or below.

   

Starter Control (Cranking Hold Function)

1. When the ECM detects a start signal from the main body ECU, the system monitors the engine speed (NE signal) and continues to operate the starter until it has determined that the engine has started. Furthermore, even if the ECM detects a start signal from the main body ECU, the system will not operate the starter if the ECM has determined that the engine has already started.

2. As indicated in the timing chart below, when the ECM detects as STSW signal (start signal) from the main body ECU, the ECM outputs a STAR signal (starter relay drive signal) through the starter cut relay to the starter relay and actuates the starter. The ECM also outputs an ACCR signal (ACC cut request signal) to the main body ECU. As a result, the main body ECU does not energize the ACC relay.

3. After the starter operates and the engine speed becomes higher than approximately 500 rpm, the ECM determines that the engine has started and stops the output of the STAR signal to the starter relay and the output of ACCR signal to the main body ECU. As a result, the starter operation stops and the main body ECU energizes the ACC relay.

4. If the engine has any failure and does not start, the starter operates as long as its maximum continuous operation time and stops automatically. The maximum continuous operation time is approximately 5 seconds through 25 seconds depending on the engine coolant temperature condition. When the engine coolant temperature is extremely low, the maximum continuous operation time is approximately 25 seconds and when the engine is warmed up sufficiently, it is approximately 5 seconds.

5. This system cuts off the current that powers the accessories while the engine is cranking to prevent the accessory illumination from operating intermittently due to the unstable voltage that is associated with the cranking of the engine.

6. This system has following protection features:

   
   

   • While the engine is running normally, the starter does not operate.

   • Even if the driver keeps pressing the engine switch, the ECM stops the output of the STAR and ACCR signals when the engine speed becomes higher than 1200 rpm. Thus, the starter operation stops and the main body ECU energize, the ACC relay.

   • If the driver keeps pressing the engine switch and the engine does not start, the ECM stops the output of the STAR and ACCR signals after 30 seconds have elapsed. Thus, the starter operation stops and the main body ECU energize, the ACC relay.

   • If the ECM cannot detect an engine speed signal while the starter is operating, the ECM immediately stops the output of the STAR and ACCR signals. Thus, the starter operation stops and the main body ECU energize, the ACC relay.