AIR INDUCTION SYSTEM - TURBOCHARGER
MX-6 Turbo, 323 Turbo and 626 Turbo models use liquid-cooled (coolant) turbochargers mounted directly to the exhaust manifold. Turbocharger consists of a turbine/compressor assembly, oil supply system and wastegate.
The safety valve of the system is a pressure actuated wastegate that prevents excess intake boost pressure. On MX-6 Turbo and 626 Turbo models, wastegate operation is also controlled by the Electronic Control Unit (ECU). The engine knock control unit senses engine knock and sends this signal to ECU. The ECU opens a wastegate solenoid valve and lowers boost pressure up to 2.2 psi.
ELECTRONIC FUEL INJECTION
The Mazda Electronic Gas Injection (EGI) computerized engine control system monitors various engine/vehicle functions to control engine operation and lower emissions while maintaining good fuel economy and driveability.
FEEDBACK CARBURETOR (B2200)
The Mazda Feedback Carburetor (FBC) computerized engine control system monitors various engine/vehicle functions to control engine operation and lower emissions while maintaining good fuel economy and driveability.
The Electronic Control Unit (ECU), through various input sensors, monitors battery voltage, engine RPM, intake air volume, cranking signal, crankshaft angle, intake air temperature, radiator and engine coolant temperatures, exhaust oxygen content, throttle position, atmospheric pressure, gearshift lever position, clutch engagement, braking, power steering operation, and A/C compressor operation. The ECU uses this input information in determining fuel injection and the actuation of other output devices. On turbocharged models spark timing is controlled by the ECU.
The ECU has a built-in fail-safe mechanism. If a fault occurs while driving, the ECU will substitute pre-programmed values. Driving performance will be affected, but the vehicle may still be driven.
The ECU has a self-diagnostic function which allows the unit to store a number of trouble codes in its memory. A Malfunction Indicator Lamp (MIL) informs the driver of system problems. The MIL is in the center of the instrument cluster, under the engine symbol marked "CHECK".
The Electronic Control Unit (ECU), through various input sensors, monitors battery voltage, engine RPM, amount of intake air, cranking signal, intake temperature, radiator and engine coolant temperatures, oxygen concentration in exhaust gases, EGR operation, throttle opening, atmospheric pressure, gearshift lever position, clutch engagement, and A/C compressor operation.
The ECU uses all input information to control air/fuel solenoid valve, idle-up solenoid valves, slow fuel-cut solenoid valve, coasting richer solenoid valve, vacuum solenoid valve, ACV solenoid valve, purge solenoid valve, and duty solenoid valve. ECU has a built-in fail-safe mechanism. If a fault occurs while driving, ECU will substitute pre-programmed values. Driving performance will be affected, but vehicle may still be driven.
Air Conditioning Switch
Closes when A/C or blower is in the "ON" position.
Airflow Meter (Inlet Air Temperature)
Varies voltage signal to ECU in relation to inlet air temperature.
Airflow Meter (Vc)
Corrected airflow meter voltage.
Airflow Meter (Vs)
Airflow position signal.
Airflow Sensor (2.6L Only)
The airflow sensor uses an electrically heated hot wire to determine the air mass entering the engine.
Atmospheric Pressure Sensor
Varies voltage signal according to altitude.
Brake Light Switch
Signals ECU of vehicle braking condition.
Coolant Temperature Sensor
Varies input voltage signal according to engine coolant temperature.
Coolant Temperature Switch
Switch opens and closes according to radiator temperature.
Distributor Signal
Signals cylinder TDC (No. 1 on 4-cylinder engines) for fuel injection timing. Detects crankshaft angle at 30 degree intervals.
Electrical Load Control
Signals ECU of additional electrical load.
Idle Switch
Indicates throttle open or closed position.
Ignition Coil
Signals engine speed.
Ignition Switch
Supplies battery voltage to ECU during engine cranking.
Inhibitor Switch (A/T)
Signals ECU of gear selection.
Intake Air Temperature Sensor (Dynamic Chamber 2.6L & 3.0L)
Varies voltage signal to ECU in relation to engine air temperature.
Knock Sensor (Turbo Only)
Sends signal to knock control unit which retards ignition timing when knocking occurs. On MX-6 Turbo and 626 Turbo, knock control unit reduces turbocharger boost pressure under knock condition.
Main Relay
Provides battery voltage to ECU.
Neutral/Clutch Switch (M/T)
Signals ECU of clutch operation and transaxle gear selection.
Oxygen (O2) Sensor
Generates voltage signal depending on oxygen content of exhaust.
Throttle Sensor
Referred to as PSW switch. Provides signal in response to wide open throttle position.
Closes when A/C or blower switch is in the "ON" position.
Varies voltage signal according to altitude.
Varies input voltage signal according to engine coolant temperature.
Switch opens and closes according to radiator temperature.
Clutch Switch
Siganls ECU of clutch engagement.
EGR Position Sensor
Detects EGR operation, sends signal to ECU.
Indicates throttle closed position.
Signals engine speed.
Supplies battery voltage to ECU during engine cranking.
Signals ECU of gear selection.
Intake Air Temperature Sensor
Detects intake air temperature, sends signal to ECU.
Signals ECU of clutch operation and transaxle gear selection.
Generates voltage signal proportional to oxygen content of exhaust gases.
Vacuum Sensor
Detects intake manifold vacuum, sends signal to ECU.
OUTPUT SIGNALS - ELECTRONIC FUEL INJECTION
The ECU processes information from the input sensors and sends appropriate voltage control signals to the following engine controls
- A/C Cut-Out System (2.6L Only - Idle Speed)
- Airflow Sensor Self-Cleaning (2.6L Only - Hot-Wire Input Device)
- By-Pass Air Control (BAC) Valve (Idle Speed)
- "CHECK ENGINE" Light (Self-Diagnostics)
- EGR Solenoid (Emission)
- Fuel Injectors (Fuel Supply)
- Fuel Pump Relay (Fuel Delivery)
- Idle Speed Control Valve (Idle Speed)
- Ignitor (Ignition)
- Knock Control Unit (Turbo Only - Ignition)
- Pressure Regulator Control Solenoid (Fuel Supply)
- Purge Control Solenoid (Emission)
- Voltage Reference (Pin Voltage)
OUTPUT SIGNALS - FEEDBACK CARBURETOR (B2200)
The ECU processes information from the input sensors and sends appropriate voltage control signals to the following engine controls
- Air Control Valve (Emission)
- Air/Fuel Valve (Fuel)
- "CHECK ENGINE" Light (Self-Diagnostics)
- Duty Control Valve (Fuel)
- EGR Solenoid (Emission)
- Idle-Up Valve (Idle Speed)
- Purge Control Solenoid (Emission)
Fuel Pump
Fuel under pressure from electric fuel pump flows through a fuel damper, fuel filter, injector fuel rail and fuel pressure regulator. Fuel pump is located in fuel tank. Electrical power for fuel pump operation during cranking mode is provided from starter relay via the fuel pump relay and ECU (fuel pump control unit on B2200 with automatic transmission).
Fuel Pump Relay
The ECU turns on the fuel pump relay based on inputs from the ignition switch and the ignition coil. During cranking, the ignition switch cranking circuit supplies current to energize the fuel pump relay. After engine starts and key is released to "RUN" position (engine speed more than 50 RPM), ECU provides fuel pump relay ground. This activates fuel pump.
Fuel Pressure Regulator
The pressure regulator is a sealed unit which is divided by a diaphragm into 2 chambers (fuel and spring chambers). The fuel chamber receives fuel through the inlet side from the injector fuel rail. The spring chamber is connected to intake manifold vacuum.
At idle, intake manifold vacuum is high. The diaphragm is pulled back by intake manifold vacuum. Any excessive fuel is returned to the fuel tank. As the throttle is depressed, intake manifold vacuum decreases. The regulator spring overcomes manifold vacuum increasing fuel pressure.
The Electronic Gasoline Injection (EGI) fuel injection system is an electronically controlled system operated by incoming air flow. The EGI fuel injection system also contains a feedback system which measures oxygen content of exhaust gases and maintains the air/fuel ratio at about 14.7:1.
The EGI fuel injection system consists of 3 major sub-systems. These are the air intake system, the fuel system, and the ECU.
The Mazda Feedback Carburetor (FBC) computerized engine control system monitors various engine/vehicle functions to control engine operation and lower emissions while maintaining good fuel economy and driveability.
The Electronic Control Unit (ECU), through various input sensors, monitors battery voltage, engine RPM, amount of intake air, cranking signal, intake temperature, radiator and engine coolant temperatures, oxygen concentration in exhaust gases, EGR operation, throttle opening, atmospheric pressure, gearshift lever position, clutch engagement, and A/C compressor operation.
The ECU uses all input information to control air/fuel solenoid valve, idle-up solenoid valves, slow fuel-cut solenoid valve, coasting richer solenoid valve, vacuum solenoid valve, ACV solenoid valve, purge solenoid valve, and duty solenoid valve. ECU has a built-in fail-safe mechanism. If a fault occurs while driving, ECU will substitute pre-programmed values. Driving performance will be affected, but vehicle may still be driven.
A/C Cut-Out System
During acceleration (60 percent throttle or more) and just after starting the engine, the ECU will open the A/C relay thereby cutting off the A/C compressor clutch. This is done to improve idle just after starting the engine and improve acceleration performance.
Under acceleration, the A/C will be cut off when the throttle valve is more than half open, transmission is in gear, and clutch pedal is released (man. trans. only). A/C is cut off for about 10 seconds. A/C will also be cut off for about 5 seconds after the engine is started.
By-Pass Air Control (BAC) Valve
The BAC valve contains an air valve and Idle Speed Control (ISC) valve. Engine coolant is directed around the air valve warming up the thermo wax. When engine coolant temperature is less than 122°F (50°C), the wax is contracted and the engine idles fast. When coolant temperature is more than 122°F (50°C), the wax is fully expanded, closing valve.
The Idle Speed Control (ISC) valve controls air by-pass amount during cold and warm engine operation. During cold engine operation, the ISC valve opens, raising fast idle speed to a predetermined RPM. The ISC valve also compensates for all engine loads during warm engine operation to maintain a preset idle RPM. The ISC is controlled by the ECU.
Scheme 1
Air By-Pass Solenoid Valve
The 626 and MX-6 models use a 3-way air by-pass system to supply additional air to the intake system. This additional air increases engine idle speed under certain driving conditions. These conditions are hot idle, operating A/C, when power steering is used at idle or when driving at high altitude.
Idle-Up Solenoids
The 323 models use up to 3 individual idle-up solenoids depending on equipment. These are electrical load, power steering and A/C idle-up solenoids. These solenoids increase engine idle speed as necessary by supplying additional air to the intake system.
Idle-Up System (B2200)
The idle-up systems are used on those models with engine powered accessories that decrease engine RPM. To maintain proper engine performance, the idle-up system increases the engine RPM to the required specifications.
B2200 models with A/C use an idle-up system, consisting of a idle-up solenoid valve, servo diaphragm, connecting hoses and electrical components. Models with A/C and auto. trans. use a dual servo diaphragm.
ELECTRONIC IGNITION SYSTEM
Mitsubishi breakerless electronic ignition consists of an ignitor, ignition coil, pick-up coil and distributor. The control module is mounted inside the distributor with the pick-up coil assembly.
When ignition is on, ignition coil primary circuit is energized. As distributor shaft rotates, the reluctor rotates inside the stator assembly.
As armature teeth pass the pegs of the pick-up coil, a signal is sent to the ignitor. The ignitor then breaks the primary circuit in the coil. This causes a high voltage surge in the coil secondary circuit. This high voltage is required to fire the spark plugs.
Altitude Timing Adjustment (B2600i & MPV 2.6L)
The atmospheric pressure sensor monitors atmospheric pressure for the ECU. The voltage signal it sends to the ECU will vary with altitude (about 4 volts at sea level). The ECU will advance ignition timing 6 degrees to compensate for loss of engine power at high altitudes. The high-altitude timing advance is canceled if the ECU test connector is grounded.
Ignition Timing Advance Control
MX-6 Turbo and 626 Turbo use an Electronic Spark Advance (ESA) that is ECU controlled. The ECU determines ignition timing based on signals from the various sensors and switches. All other models use centrifugal and vacuum advance units located in the distributors.
Detonation (Knock) Retard Operation
Turbocharged models use a ignition retard system consisting of a knock sensor and knock control unit. The knock sensor detects detonation in the engine and sends a signal to knock control unit. This signal is modified by the knock control unit and sent to the ECU. Timing is retarded up to 6 degrees, depending upon severity of knocking. On MX-6 Turbo and 626 Turbo models, knock control unit also controls turbocharger wastegate solenoid valve, which lowers boost pressure up to 2.2 psi during knock conditions.
DECELERATION CONTROL SYSTEM
To reduce emissions and increase fuel economy during deceleration, B2200 models are equipped with a deceleration control system. Deceleration control system on B2200 models consists of a slow fuel-cut solenoid valve, a coasting richer solenoid valve, vacuum solenoid valve dash pot and mixture control valve.
Slow fuel-cut solenoid valve closes primary slow fuel passage on command from ECU. Coasting richer solenoid valve supplies extra fuel/air mixture to add to primary slow fuel on command from ECU. Vacuum solenoid valve supplies intake manifold vacuum to distributor vacuum advance on command from ECU. Dashpot causes throttle valve to close gradually. Mixture control valve supplies air into intake during first stage of deceleration.
EXHAUST GAS RECIRCULATION (EGR) CONTROL
The Exhaust Gas Recirculation (EGR) system allows measured amounts of exhaust gas into the intake manifold to reduce oxides of nitrogen (NOx).
The EGR system on B2200 models consists of EGR control valve, EGR valve position sensor, duty solenoid valve, and connecting hoses and pipes.
The EGR system on MX-6 and 626 models consists of EGR control valve, EGR modulator valve (non-turbo), EGR solenoid valve (non-turbo), EGR position sensor (turbo), duty solenoid valve (turbo), vacuum check valve, and connecting hoses and pipes.
FUEL EVAPORATION SYSTEM
Fuel evaporation system prevents escape of raw fuel vapor to atmosphere. Components of system include a fuel tank with integral vapor separator, a check and cut valve (3-way valve on MX-6 and 626), a air vent solenoid valve (B2200), a purge control solenoid valve (B2600i), 2 purge control valves (3 on 323, MX-6 and 626), a charcoal canister, a fuel filler cap, a coolant thermovalve (except 323) and connecting lines.
Additional components include, a 3-way solenoid valve on MX-6 and 626 (2 on 323), and Emission Control Unit (ECU).
HOT IDLE COMPENSATION SYSTEM (B2200)
On B2200 models, hot idle compensation system supplies additional air to the intake manifold to maintain smooth idle and reduce emissions. B2200 models use an idle compensator valve. When intake air temperature is more than 145°F (63°C), the idle compensator valve opens and allows air directly into the intake manifold.
REED VALVE AIR INJECTION (B2200)
Air injection system draws atmospheric air into the exhaust system to reduce CO and HC emissions. Basic system components consist of a reed valve assembly, air control valve(s), catalytic converter(s) and connecting hoses and pipes.
THERMOSTATIC AIR CLEANER
The Thermostatic Air Cleaner system controls the temperature of the air entering the carburetor depending on outside air temperature. On B2200 models, thermostatic air cleaner system consists of air cleaner housing, bi-metal control valve, flexible air hose, and heat stove.
A control valve, controlled by air temperature, opens to allow warm air from heat stove to mix with fuel. This assists in engine warm up, better combustion and emission control.
CHECK ENGINE LIGHT
Lights during engine start up and monitored component malfunction. Is also referred to as MIL or Malfunction Indicator Light. MIL is also used to read trouble codes.