B230FT Engine (Turbo)

Fig. 120 EXHAUST GAS RECIRCULATION SYSTEM (CALIFORNIA MARKET ONLY):

Exhaust gas recirculation (applicable to California market only) is used to reduce the content of nitrogen oxides (NOx) in the exhaust. NOx are formed at the high temperatures which occur in the combustion chambers at high engine loads.
Reintroducing a proportion of the exhaust gases into the combustion chamber reduces combustion temperature, with an attendant reduction in the nitrogen oxide content. Fig. 120.
The system is not activated when the engine is cold or idling. Under these conditions, the NOx level is already low and recirculation would impair the running of the engine.
Recirculation is controlled by the E.G.R. vacuum valve which, in turn, is controlled by the ignition system control unit via the E.G.R. vacuum booster. The vacuum booster is supplied, by the control unit, with a signal which is a function of the engine speed, load and temperature. Combined with the ambient pressure and the pressure in the intake manifold, this signal is converted into a control pressure signal which operates the E.G.R. vacuum valve via a vacuum hose.


COMPONENTS:
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Fig. 121 E.G.R. VALVE:

E.G.R. VACUUM VALVE
The E.G.R. vacuum valve controls the flow of gases from the exhaust manifold to the intake manifold. The valve is operated by the control pressure in the vacuum hose from the E.G.R. vacuum booster. Fig. 121.
The E.G.R. vacuum valve is located under the intake manifold.

Fig. 122 E.G.R. VACUUM BOOSTER:

E.G.R. VACUUM BOOSTER
The vacuum booster controls the pressure in the vacuum to the E.G.R. vacuum valve by means of the admission valve (lower section). The pressure in the intake manifold is supplied to the reducing valve (upper section). The vacuum booster processes the electrical signal from the control unit and the pressure signal from the intake manifold to maintain optimum control of the E.G.R. vacuum valve. The unit also makes allowance for the ambient air pressure. Fig. 122.
The E.G.R. vacuum booster is mounted on the left-hand suspension strut tower.

Fig. 123 E.G.R. TEMPERATURE SENDER:

TEMPERATURE SENDER
The sender measures the temperature of the exhaust gases returned to the intake manifold. By detecting temperature variations, the control unit can determine whether or not the E.G.R. system is operating. The sender is of the PTC (positive temperature coefficient) type and is designed to measure temperatures up to 500°C (932°F). PTC means that the resistance increases with temperature. Fig. 123.
Since the sender is highly sensitive to shock and impact, particular care must be taken when handling and installing it.
This sender is mounted in the E.G.R. upper pipe between the intake manifold and E.G.R. vacuum valve.

Fig. 124 EGR UPPER PIPE:

E.G.R. UPPER PIPE
The E.G.R. upper pipe transfers the gases from the E.G.R. vacuum valve to the intake manifold. The new design of pipe is provided with a 6mm tap hole for the temperature sender probe and with a dimple to ensure that the probe is not forced against the bottom of the pipe if the sender is tightened to an excessive torque. Fig. 124.