Fuel System Regina
DESIGN AND FUNCTION
Fuel system Regina
The Regina fuel system can be divided into five sub-systems.
- The control system regulates fuel and air quantity to ensure the optimal blend of air and correct idle speed.
- The sensor system provides information to the control system for optimal control.
- The fuel distribution system is regulated by the control system and it distributes fuel to the cylinders.
- The EVAP system takes care of those gases which evaporate in the tank; it is controlled by the negative pressure in the intake manifold.
- The diagnostic system has three diagnostic modes to simplify troubleshooting. Refer to Rex I Design and Function.
Regina sensor system
Pressure sensor
The pressure sensor is connected via a hose to the intake manifold, so as to sense the air pressure there. Pressure is converted to an electrical signal via a piezo-electrical crystal in the sensor.
The pressure sensor is sensitive to electrical interference and is therefore sheathed in a metal casing.
When the ignition is switched on and under full load, atmospheric pressure is registered so that an adjustment can be made for changes in atmospheric pressure.
Temperature sensor, intake air
Air in the intake manifold passes through a hole in the sensor and affects a probe. The probe's resistance reduces with increasing temperature (NTC=Negative Temperature Coefficient).
With the help of signals from the pressure sensor and temperature sensor for intake air, the control unit can calculate the volume of air which is inducted into the engine.
Temperature sensor, engine
The sensor is mounted in the cylinder head and is immersed in coolant. The sensor has two resistors, one for the fuel and one for the ignition system. Resistance is reduced with increasing temperature (NTC=Negative Temperature Coefficient).
Throttle switch
The throttle switch has two switches for idle and full throttle respectively.
It provides signals to the fuel system's and ignition system's control unit regarding shut or fully open throttle valve.
Lambdasond
An assessment of the ratio between air and fuel is obtained by measuring the oxygen content of the exhaust gases after the combustion process, using a lambdasond.
The signal from the lambdasond has a voltage whose level depends on the oxygen content of the exhaust gases. This signal varies from high (>0.9 V) to low (<0.1 V) at the ideal ratio of 14.7kg air/1 kg fuel. A rich mixture provides a high voltage while a lean mixture provides a low voltage. Based on this signal, the control unit regulates the injection timing continuously so that the ideal ratio is maintained.
The lambdasond only functions above a certain temperature, approx. 285°C. This is why it is electrically heated, so that it can quickly reach operational temperature. When the ignition is switched on, a PTC-resistor (PTC= Positive Temperature Coefficient) is connected, whose resistance in creases with a rise in temperature. This resistor provides a short warming-up time and it keeps the sond at the correct temperature when exhaust temperature is low.
Catalytic converter 3-way
The catalytic converter effectively reduces the levels of carbon monoxide, oxides of nitrogen and hydrocarbons in the exhaust gases
The catalyst is of the three-way type and cleans the exhaust as follows:
- Unburned hydrocarbons (HC) are oxidized to water vapor (H2O) and carbon dioxide (CO2)
- Carbon monoxide (CO) is oxidized to carbon dioxide (CO2)
- Oxides of nitrogen (NOx) are reduced to nitrogen gas (N2)
In order for the catalyst to function as intended, it is necessary for the lambdasond to provide the correct signal so that no unburned fuel mixes with the exhaust gases. Otherwise the catalytic converter can be damaged by excessive temperature.
Regina control system
Control unit
Control of injection timing
In normal driving, a basic injection timing is calculated by the control unit based on the data relating to air mass, oxygen content of the exhaust gases, engine speed and battery voltage. The control unit then adjusts this basic timing under certain conditions to provide optimal combustion and best function.
- At start a special program is used, offering two injection cycles per engine revolution.
- At very low engine temperature (below approx. -18°C) and low engine speed the cold-start valve too is operated.
- At temperatures below 60°C a richer mixture is provided.
- When the throttle switch indicates full load, the injection timing is increased.
- The injectors are shut during engine braking.
- Fuel injection is switched off on over-run.
Emergency function
The control unit has "limp-home"-functions so that the car can be driven even if a signal is missing.
The system is reversible, which means that if the signal returns with adequate values after a period of faulty readings, the control unit will utilize the measured values once again instead of continuing to use the "limp-home" facility.
- If one or both of the signals from the intake air pressure or temperature sensor fail to get through, injection timing will vary depending on the engine speed.
- If the engine temperature signal is missing, injection timing will be as for a hot engine. As a result, the lack of the engine temp. signal will be most noticeable during cold starts.
Idle speed regulation
The control unit bases regulation of idle speed on engine temperature and whether or not the throttle valve is in the idle position. The control unit also regulates the idle valve so that constant idle speed is obtained in the following cases.
- If the AC-button is switched on.
- If the AC-compressor is operating.
- It the gear selector in an automatic car is moved from Park or Neutral.
In order to avoid excessive idle speed, for example owing to an incorrectly adjusted throttle valve, the idle valve receives a signal which virtually corresponds to an opening angle of 0 %. Engine idle speed will be just over 1000 rpm.
Adaptive idle speed control
The B 230F does not have basic engine speed adjustment. Instead, the control signal to the idle valve is based on information received by the control unit over a long period of time. The signal is adjusted to compensate for ageing, dirt accumulations or minor air leakage, so that a constant idle speed is obtained even when the engine has aged.
Adaptive Lambdasond regulation
With the adaptive lambdasond regulation, the control unit can adjust injection timing to compensate for engine wear, minor air leakage, clogged injectors etc. so that the lambdasond can operate under optimum conditions. The correct fuel ratio is obtained even after engine braking and before the lambdasond has been warmed up, which would otherwise not be the case.
The adaptive lambdasond regulation system consists of two phases, additive and multiplicative compensation. Additive compensation affects injection timing swiftly and mostly at low engine speeds such as when idling. Additive control corresponds to the basic CO adjustment which is made in other systems using a potentiometer. Multiplicative control has a greater effect during longer changes.
The ability to compensate is limited and in the event of major interference, the limit will be exceeded. The control unit will then set fault code 2-3-1 or 2-3-2, depending on whether it is the multiplicative or additive compensation which has been exceeded.
Idle valve
When the idle switch is on, the valve controls the amount of air which flows past the throttle valve. The engine's idle speed is thus kept constant irrespective of load from the automatic gearbox, AC unit, power steering or alternator.
In addition, under engine braking it supplies air to the engine so that negative pressure is maintained in the intake manifold at a permitted level. In order to control this swiftly, the idle valve assumes a monitoring setting when the idle switch is not closed.
Fuel distribution system
The fuel pump draws fuel from the fuel tank and passes the fuel through a filter to the distribution pipes on the engine The distribution pipe features a pressure regulator, injectors and cold-start valve.
Pressure regulator
The pressure regulator keeps the fuel under constant pressure in relation to the negative pressure in the intake manifold.
Injectors
This is equipped with a solenoid and fuel needle which opens and shuts a nozzle.
The control unit grounds the injectors during the calculated time period so that the valves open and inject fine droplets of fuel. Injection takes place through all the injectors simultaneously, once per engine revolution during driving and twice if the engine is coId~ Fuel is injected in the intake manifold near the intake valves.
An injector which has been removed may only be tested with special fluid since fuel spray is particularly volatile and explosive.
Cold start valve
The cold start valve improves the cold starting characteristics. It has a similar design to that of the injectors.
In cold starts, a lot of fuel is condensed in droplet form on the cold surfaces. The cold start valve is thus located further away from the engine than the injectors and it supplies the fuel more in gas form than In droplet form.
The cold start valve is activated at approx. 1S~C and at engine speeds under approx. 600 rpm. When one of the limits is exceeded, the cold start valve is shut. On certain models, the cold start valve is connected to the starter motor so that it can only be activated when the engine is started.
On certain cars, voltage supply is connected to the starter motor so that injection can only take place when the engine is cranked. The engine speed and temperature limits are the same.
EVAP system
EVAP stands for Evaporative Control System and it is a vacuum-controlled system which deals with those gases which evaporate from the fuel in the fuel tank, preventing them from being released into the atmosphere.
Cannister
Fuel vapor passes through a hose system from the)top of the fuel tank's filler pipe to a container (cannister) featuring a coal filter which absorbs the fuel vapor.
EVAP valve
The EVAP valve is located on the cannister and it is connected to the intake manifold. This valve ensures that fuel vapor does not get to the engine if the engine is switched off or is operating at idling speed.
Roll-over valve
The Roll-over valve shuts off the system if the car leans more than 45 degrees, thus preventing fuel from leaking in the event of an accident.