Flow chart
| reference | designation | part number in the electrical diagrams |
|---|---|---|
| 1 | inlet camshaft dephaser (VVT) | |
| 2 | Induction camshaft | |
| 3 | cylinder reference sensor | 1115 |
| 4 | engine speed sensor | 1313 |
| 5 | engine ECU | 1320 |
| 6 | oil pump | |
| 7 | solenoid valve controlling the camshaft dephaser | 1268 |
| "a" | delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (A) | |
| "b" | delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (B) | |
| "c" | return of oil towards the engine sump | |
| "d" | delivery of engine oil under pressure into the variable timing electrovalve |
Motorised throttle housing (1262)
Role
Dose the quantity of air admitted in the cylinders
The request to open the air regulating flap is no longer a direct command by cable linked to the accelerator pedal
An accelerator pedal sensor informs the injection ECU of the driver's request
The injection ECU then commands the butterfly housing motor
A potentiometer incorporated in the throttle housing allows the injection computer to determine the exact position of the air regulating flap
Description
Make Magneti Marelli 50 SP1
Direct current motor
Direct current motor controlled by open cycle ratio (OCR)
Double-track contact potentiometer
Butterfly diameter: 50 mm
Electrical special features
Allocation of channels of connector
- Terminal 1: earth (2 potentiometers)
- Terminal 2: butterfly position signal for track no.1 (graph rising at the opening of the butterfly)
- Terminal 3: supply of butterfly motor (+)
- Terminal 4: supply of butterfly motor (-)
- Terminal 5: supply of the potentiometers 5 volts
- Terminal 6: butterfly position signal for track no.2 (graph descending at the opening of the butterfly)
Solenoid valve controlling the camshaft dephaser (1268)
Role
The camshaft dephaser control electrovalve (1268) hydraulically controls the inlet camshaft dephaser (VVT)
NoteThe engine ECU pilots the camshaft dephaser control electrovalve (1268) as a function of engine speed and engine load
Description
"A": representation of the camshaft dephaser control electrovalve
"B": hydraulic representation of the camshaft dephaser control electrovalve
"a": delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (A)
"b": delivery of engine oil under pressure into the camshaft dephaser control electrovalve (1268)
"c": delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (B)
"d": return of oil towards the engine sump
Typical graph for the camshaft dephaser control electrovalve
"a": delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (A)
"b": delivery of engine oil under pressure into the camshaft dephaser control electrovalve (1268)
"c": delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (B)
"d": return of oil towards the engine sump
"C": flow of engine oil
"D": control power of the camshaft dephaser control electrovalve (amps)
"E": oil delivery phase for chambers (B) and oil return phase for chambers (A)
"F": oil delivery phase for chambers (A) and oil return phase for chambers (B)
Electrical special features
Control: injection ECU (earth)
All or nothing control
Allocation of channels of connector
- Terminal 1: 12 Volts
- Terminal 2: earth
Location
(7) solenoid valve controlling the camshaft dephaser
Location: to the centre of the cylinder head close to the timing covers
Engine chart
"S": inlet and exhaust valves crossing time
"T": inlet valves opening time
"U": exhaust valves opening time
"G": before top dead centre (BTDC)
"H": after bottom dead centre (ABDC)
"J": before bottom dead centre (BBDC)
"K": after top dead centre (ATDC)
"L": intake phase = descent of piston
"P": compression phase = rising of piston
"N": combustion phase = descent of piston
"M": exhaust phase = rising of piston
"Q": inlet
"R": exhaust
NoteCrossing of the inlet and exhaust valves occurs only between the exhaust phase "M" and the inlet phase "L"
If the inlet camshaft dephaser (VVT) increases the inlet closing retard (H), the inlet opening advance (G) is proportionately reduced
Inlet camshaft dephaser (VVT)
Role
Functions of the intake camshaft dephaser
- To dephase the inlet camshaft in relation to its drive in certain phases of engine operation (offset of camshaft 20° maximum)
- To adapt the quantity of air admitted to the engine load
- To improve engine performance (especially the engine torque at low engine speeds)
Description
The inlet camshaft dephaser (VVT) is controlled by the engine oil pressure
The camshaft dephaser control electrovalve (1268) distributes the engine oil under pressure into the 5 chambers (A) or the 5 chambers (B)
The difference in oil pressure between chambers (A) and (B) offsets the inlet camshaft
"e": chamber (A) of the camshaft dephaser
"f": chamber (B) of the camshaft dephaser
"g": camshaft dephaser locking pin (engine not running)
"h": delivery and return channel for chambers (A)
"j": delivery and return channel for chambers (B)
NoteThe pin "g" locks the position of the inlet camshaft dephaser (VVT) when the oil pressure is low. the pin "g" unlocks the position of the inlet camshaft dephaser (VVT) as soon as the oil pressure in chamber A reaches around 0,5 bars
Maximum inlet closing retard (RFA) position
NoteThe inlet closing retard (RFA) is at maximum when the camshaft dephaser control electrovalve is not supplied (the inlet opening advance (AOA) is at minimum when the camshaft dephaser control electrovalve is not supplied)
The inlet closing retard (RFA) is increased in the following cases
- Engine speed high and under load: the inlet camshaft dephaser (VVT) retards the closing of the inlet valves in order to favour the filling with air
- Idling speed: the inlet camshaft dephaser (VVT) retards the closing of the inlet valves in order to reduce the inlet opening advance (AOA) and thus reduce the crossing of the inlet and exhaust valves (optimum combustion)
"a" delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (A)
"b" delivery of engine oil under pressure into the camshaft dephaser control electrovalve (1268)
"c" delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (B)
"d" return of oil towards the engine sump
The engine oil pressure supplies the chambers (A)
The chambers (B) are in communication with the engine oil return circuit
Minimum inlet closing retard (RFA) position
In minimum inlet closing retard (RFA) position, the crossing of the inlet and exhaust valves is at maximum
"a" delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (A)
"b" delivery of engine oil under pressure into the camshaft dephaser control electrovalve (1268)
"c" delivery or return of engine oil for the inlet camshaft dephaser chambers (VVT) (B)
"d" return of oil towards the engine sump
The engine oil pressure supplies the chambers (B)
The chambers (A) are in communication with the engine oil return circuit
Stabilised position
The camshaft dephaser control electrovalve (1268) stabilises the position of the inlet camshaft dephaser (VVT) by supplying alternately chambers (A) and (B)
Inlet manifold pressure and inlet air temperature sensor (1312)
NoteThe atmospheric pressure sensor is integrated in the engine ECU
Role
The sensor makes it possible to determine the air pressure in the inlet manifold and the temperature of the inlet air
The inlet manifold pressure measurement enables the ECU to define the weight of air entering the engine in order to dose the quantity of petrol
NoteThe density of the air decreases according to the altitude
Description
"k" air entry
The pressure sensor supplies a voltage proportional to the air pressure in the inlet manifold
Electrical special features
Allocation of channels of connector
- Terminal 1: signal (inlet air pressure)
- Terminal 2: 5 Volts
- Terminal 3: signal (inlet air temperature)
- Terminal 4: earth
Location
8: inlet manifold
9: inlet manifold pressure and inlet air temperature sensor (1312)
"l": vacuum oulet towards brake servo
"m": canister inlet