OPERATION

2.4 JTD 10V

At coolant temperatures of > 20°C with the engine speed between 800 and 3000 rpm, the engine management control unit operates the EGR solenoid valve with a square wave signal.

The variation in this signal allows the EGR coil to move a shutter, thereby regulating the flow of exhaust gases from the exhaust manifold to the intake manifold; there are two results:

• less air is introduced
• the combustion temperature is reduced (on account of the presence of inert gases) resulting in a decrease in the formation of NOx (nitrogen oxides).

The engine management control unit is constantly informed of the quantity of gas recirculated through the information coming from the flow meter: in effect, if there is an intake of a certain quantity of air (Qam) for a given engine speed and the value sent by the flow meter (Qar) is lower, then the difference (Qgr) is the value for the quantity of gas recirculated

- Qam - Qar = Qgr

- Qam = theoretical quantity of air memorized

- Qar = quantity of actual air

- Qgr = quantity of recirculated gases

The atmospheric pressure signal is used for the operation of the EGR solenoid valve to recognize the condition of driving at altitude in order to reduce the quantity of gas recirculated and to prevent engine fumes.

EGR SOLENOID VALVE

Specifications

The Pierburg EGR solenoid valve, fitted on the intake manifold, has the task of modulating the flow of exhaust gases to the intake according to the command from the injection control unit.

This modulation takes place by means of the internal solenoid, with PWM operation by the control unit, which activates the control rod via the internal valve.

• 1 EGR valve body
• 2 inner valve
• 3 gas intake from exhaust manifold
• 4 gas outlet to intake manifold

2.0 TB

LAMBDA SENSORS

These are planar type and located upstream and downstream of the catalytic converter.

The upstream sensor determines mixture control, known as the first loop.

The control unit controls and manages injection so that the air/fuel ratio is always sufficiently close to a stoichiometric level to maximise catalytic converter efficiency. The mixture is enriched to ensure maximum performance under conditions of full power and high use.

The downstream sensor diagnoses the conversion efficiency of the converter/s.

Then:

• lambda = 1 ideal mixture.
• lambda %gt; 1 lean mixture.
• lambda %lt; 1 enriched mixture.

• a - Enriched mixture (less air).
• b - Lean mixture (excess air).

When it comes into contact with the exhaust gases, the lambda sensor generates an electrical signal with a voltage value dependent upon oxygen levels present in the gas. This voltages alters abruptly when mixture composition deviates from lambda = 1.

The injection control unit manages lambda sensor heating in proportion with exhaust gas temperature.

This prevents thermal shocks to the ceramic casing due to contact with condensed water present in the exhaust gases when the engine is cold.

The measurement chamber and heater are built into a planar (laminated) ceramic element that offers the benefit of fast chamber heating. This allows closed loop (lambda = 1) control within 10 second of engine start-up.

• 1 Connection cable.
• 2 Protective sleeve.
• 3 Planar sensor element.
• 4 Ceramic mounting pipe.
• 5 Sensor housing.
• 6 Ceramic gasket.
• 7 Protective pipe.

The lambda sensor works on the principle of an oxygen concentration chamber with solid electrolyte.

The measuring chamber surfaces are coated with microporous layers of noble metal.

• 1 exhaust gas.
• 2 Reference air passage.
• 3 Heater
• 4 Lambda sensor voltage.

Specifications:

• Power supply: 12V
• Internal resistance: 0.5 %divide; 1 kOhm.

CATALYTIC CONVERTER

The three-way catalytic converter makes it possible to keep down the levels of the three pollutant gases in the exhaust gases at the same time:

• unburnt hydrocarbons (HC);
• carbon monoxide (CO);
• nitrogen oxides (NOx).

Two types of chemical reaction take place inside the converter:

• oxidation of CO and HC to carbon dioxide (CO2) and water (H2O);
• reduction of Nox to nitrogen (N2).

The converter consists of a structure, a metal gauze support to dampen impacts and vibrations and a stainless steel outer casing that is resistant to high temperatures and atmospheric agents. The honeycomb structure is made from a ceramic material covered in an extermely thin layer of catalytically active substances, platinum or rhodium, which accelerated the chemical decomposition of the harmful substances contained in the exhaust gases which, when passing through the core cells at temperatures above 300° ÷ 350°C, activate the catalyzers setting off the oxidation/reduction reactions.

The nobile metals in the catalytic converter suffer chemical attack if lead is present, partly due to the high temperature inside the converter. For this reason, the use of leaded fuel should be be avoided, otherwise the converter will be rapidly and irreversibly put out of service. Never use leaded fuel, even for a short time in an emergency.

• 1 One-piece ceramic structure
• 2 Metal mount
• 3 Outer casing
• 4 Perforated steel cone

3.0 V6, 3.2 V6

LAMBDA SENSORS

These planar sensors are fitted: on the two catalytic preconverters and the two catalytic converters. They inform the injection control unit about combustion progress (stoichiometric ratio).

The upstream sensors monitor concentration and are known as the 1st loop (closed loop of upstream sensor).

The sensors downstream of the catalytic converter are used to for converter diagnostics and to fine-tune 1st loop control parameters.

The second loop is therefore adaptive to make up for production discrepancies and slight drift that upstream sensor responses could experience due to ageing and contamination.

This control is known as 2nd loop control (downstream sensor closed loop).

The electronic control unit identifies mixture composition (lean or rich) from the lambda sensor output voltage.

This adjusts injected fuel quantity to ensure optimum mixture composition (%lgr; = 1 to create ideal conditions for treatment of exhaust gas in the catalytic converter.

If the mixture is too rich (%lgr; %lt; 1) fuel quantity must be reduced and if the mixture is too lean (%lgr; %gt; 1), fuel quantity must be increased.

• a, Righ mixture (not enough air).
• b, Lean mixture (too much air).

The lambda sensors are in contact with exhaust gases and generate an electrical signal with voltage dependent on oxygen level in the gas.

This voltage changes abruptly when mixture concentration deviates from a value of %lgr; = 1.

The injection control unit manages lambda sensor heating in proportion with exhaust gas temperature.

This avoids thermal shocks to the ceramic case due to contact with condensed water present in exhaust gas when the engine is cold.

The measurement chamber and heater are built into a planar (laminated) ceramic element. This offers the benefit of fast chamber heating to allow closed loop control (%lgr; = 1) within 10 seconds of engine start-up.

• 1, Connection cable.
• 2, Protective sleeve.
• 3, Planar sensor element.
• 4, Ceramic mount pipe.
• 5, Sensor seat.
• 6, Ceramic gasket.
• 7, Protective pipe.

The lambda sensor works on the principle of an oxygen concentration chamber with solid electrolyte.

The measurement chamber surfaces are coated with microporous layers of noble material.

• 1, Exhaust gas.
• 2, Reference air passage.
• 3, Heater.
• 4, Lambda sensor voltage.

Specifications:

• Fuel system: 12 V
• Internal resistance: 0.5 %divide; 1 kOhm.

CATALYTIC CONVERTER

The three-way catalytic converter makes it possible to keep down the levels of the three pollutant gases in the exhaust gases at the same time:

• unburnt hydrocarbons (HC);
• carbon monoxide (CO);
• nitrogen oxides (NOx).

Two types of chemical reaction take place inside the converter:

• oxidation of CO and HC to carbon dioxide (CO2) and water (H2O);
• reduction of NQx to nitrogen (N2).

The converter consists of a structure, a metal gauze suppoart to dampen impacts and vibrations and a stainless steel outer casing that is resistant to high temperatures and atmospheric agents.

The honeycomb structure is made from a ceramic material covered in an extermely thin layer of catalytically active substances, platinum or rhodium, which accelerated the chemical decomposition of the harmful substances contained in the exhaust gases which, when passing through the core cells at temperatures above 800°C ¸ 350°C, activate the catalyzers setting off the oxidation/reduction reactions.

A perforated steel cone improves the diffusion of the exhausts gases in the ceramic core cells to ensure the optimum efficiency and lifespan of the catalyzer.

As a result of the high temperature in the catalytic converter, the noble metals are chemically attacked by any lead present. For this reason the use of petrol containing lead should be avoided as it will cause rapid and irreversible damage to the converter. Never use petrol containing lead, even very briefly or in cases of emergency.

• 1, One-piece ceramic structure.
• 2, Metal support.
• 3, Outer casing.
• 4, Perforated steel cone.

2.4 JTD 20V

At coolant temperatures of > 20°C with the engine speed between 800 and 3000 rpm, the engine management control unit operates the EGR solenoid valve with a square wave signal.

The variation in this signal allows the EGR coil to move a shutter, thereby regulating the flow of exhaust gases from the exhaust manifold to the intake manifold; there are two results:

• less air is introduced
• the combustion temperature is reduced (on account of the presence of inert gases) resulting in a decrease in the formation of NOx (nitrogen oxides).

The engine management control unit is constantly informed of the quantity of gas recirculated through the information coming from the flow meter: in effect, if there is an intake of a certain quantity of air (Qam) for a given engine speed and the value sent by the flow meter (Qar) is lower, then the difference (Qgr) is the value for the quantity of gas recirculated

- Qam - Qar = Qgr

- Qam = theoretical quantity of air memorized

- Qar = quantity of actual air

- Qgr = quantity of recirculated gases

The atmospheric pressure signal is used for the operation of the EGR solenoid valve to recognize the condition of driving at altitude in order to reduce the quantity of gas recirculated and to prevent engine fumes.

EGR SOLENOID VALVE

Specifications

The Pierburg EGR solenoid valve, fitted on the intake manifold, has the task of modulating the flow of exhaust gases to the intake according to the command from the injection control unit.

This modulation takes place by means of the internal solenoid, with PWM operation by the control unit, which activates the control rod via the internal valve.

• 1 EGR valve body
• 2 inner valve
• 3 gas intake from exhaust manifold
• 4 gas outlet to intake manifold
• 5 5V potentiometer power supply
• 6 Potentiometer negative
• 7 Solenoid negative
• 8 Potentiometer positive signal