All engines
The heating process itself is divided into three phases.
«Pre-glow»: with key turn «ignition» in the first position of the ignition switch you start the preglow process, the preglow relay (47 kW motor) or a control device for automatic heating time (55 kW motor) give an order «Warm up the engine!» How long to warm up, determines the electronic control itself. The colder the coolant, the longer it takes to warm up.
The temperature information for this control system receives from the temperature sensor (arrow) in the coolant fitting on the cylinder head. With a cold engine, the relay and control unit energizes the glow plugs for about 9 seconds.
With a warm or warm engine, the pre-glow time is correspondingly shorter or there is no warm-up at all (at coolant temperature over +65°С). If the warm-up time has elapsed, the pre-glow indicator on the instrument panel will go out - the engine can be started
Ready to start: since the driver sometimes does not start the engine immediately after the indicator light goes out, then for safety net after 10 seconds. glowing is repeated, and heating is also repeated when the starter is turning - no matter how long this process continues. wire terminal «50» signals to the control electronics whether the starter is engaged.
Subsequent heating; when the engine is started, the post-glow time begins - it lasts up to 180 seconds, until the temperature of the coolant passes the value of +65°C. The purpose of the post-warm-up is to reduce the combustion noise of a still cold engine and to improve the composition of the exhaust gases in the cold phase.
Additional features for a 55 kW turbodiesel
The control device for the automatic glow time also regulates some additional functions.
Preglow control via contact switch in the door: After entering the vehicle, closing the driver's door already starts the temperature-dependent glowing process on this engine. When the driver wants to start the engine, by this time the pre-glow has basically ended (the pre-glow indicator lamp no longer lights up). The door game does not work when the engine is already running or when the door is opened and closed several times in a row.
Management of switchable, load-dependent injection timing; The load-dependent injection timing is switched on and off by the control unit for the automatic glow-in time depending on the speed (see chapter «Diesel injection system»).
Raising the idle speed: the device for increasing the idle speed, installed on vehicles with air conditioning, prevents «failures» in the operation of the engine at idle when the air conditioner compressor is turned on. At the same time, the vacuum system moves the idle speed setting lever on the injection pump in the direction «full throttle». The vacuum valve is also controlled by the automatic glow time control device.
Glow plug current control
The starter during operation puts a heavy load on the battery, consuming a lot of current. Consequence: Mains voltage drops (sometimes up to 8 V). The glow plugs are not receiving the necessary voltage to reach the correct temperature. This effect is circumvented by the use of so-called self-adjusting glow plugs. They are designed in such a way that even at low mains voltage they still reach the desired temperature of 800-1000°C. Usually, with this design and a normal voltage of 12-14 V, they would overheat and burn out. But here the effect of self-regulation of glow plugs works. On the basis of the temperature/resistance ratios, the plugs themselves regulate the flow of current and, accordingly, the glow temperature. Thus, it is guaranteed that at a voltage of 14 V the filament temperature will never exceed 1050°C.
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