Ignition and Control Systems - Design and Function (Coupe): Overview Volvo C70 I

Overview

The function of the turbocharger (TC) control system is to optimize boost pressure and, as a result, engine output under the most variable conditions. As boost pressure is controlled electronically, the turbocharger (TC) delivers full output at a speed as low as 1800 RPM which means that it provides high torque at all engine speeds. Turbocharger (TC) boost pressure is controlled by the engine control module (ECM).

Scheme 1059

Scheme 1060

The turbocharger (TC) system is designed to increase engine output. This is achieved by compressing the intake air in the turbocharger (TC). The system senses that more air in entering the cylinder and so injects more fuel. The cylinder is filled with more air and fuel than it could suck in. The pressure that occurs is called turbocharger (TC) boost pressure.

Exhaust gases pass through (1) to the turbocharger (TC) driving the rotor. They then pass out through exhaust pipe (2). Fresh air is sucked in through (3) and pressed through (4) via the charge air cooler (CAC) into the intake manifold.

The engine control module (ECM) also provides other units in the car with signals and information calculated using the sensors.

The following units receive information from the engine control module (ECM)

1. transmission control module (TCM)
2. combined instrument panel.
3. trip computer
4. air conditioning (A/C) compressor via air conditioning (A/C) relay.

Scheme 1061

The transmission control module (1) receives the following information from the engine control module (ECM) (2)

1. engine air mass and speed from the mass air flow (MAF) sensor (3)
2. throttle angle from the throttle position (TP) sensor (4).

The transmission control module (TCM) uses this information to calculate gear shifting.

Scheme 1062

The trip computer obtains information about the quantity of fuel injected from the engine control module (ECM).

This information is used to display fuel consumption.

Scheme 1063

The engine control module (ECM) controls the following components and functions on the basis of these input signals

1. main relay (2/32)
2. fuel pump (FP), by activating the fuel pump (FP) relay (2/23)
3. fuel injection, by individually activating injectors (8/6-8/10)
4. ignition, by transmitting signals to the ignition discharge module (IDM) integrated with the ignition coil (4/44)
5. idling speed, by operating the idle air control (IAC) valve (8/5)
6. pressure in the inlet manifold during engine braking by regulating the idle air control (IAC) valve (8/5)
7. engine cooling fan (FC), by activating the fan control (FC) relay (2/11)
8. turbocharger (TC) boost pressure, by controlling the turbocharger (TC) control valve (8/28)
9. EVAP-system canister purge (CP) valve (8/18)
10. malfunction indicator lamp (MIL) (10/106) for emission-related faults
11. preheating of front and rear heated oxygen sensors (HO2S) (7/15 and 7/82)
12. air conditioning (A/C) compressor relay (2/22), for shutting-off compressor.
13. EVAP canister shut-off valve (8/44), certain markets only.
14. pulsed secondary air injection system (PAIR) pump valve (8/43)
15. pulsed secondary air injection system (PAIR) pump, by activating the pulsed secondary air injection system (PAIR) pump relay (2/53).

Scheme 1064

The Motronic 4.4 is an electronic engine management system which controls

1. fuel injection
2. ignition
3. idling speed
4. turbocharger (TC) boost pressure
5. engine cooling fan (FC)
6. EVAP system
7. air conditioning (A/C) system
8. pulsed secondary air injection system (PAIR).

The engine control module (ECM) incorporates a micro-processor which receives signals from the various sensors in the car. This micro-processor uses a program to compute the necessary engine management functions.

The engine control module (ECM) incorporates adaptive functions, which enable it to adjust its computations continuously to suit running conditions.

By managing the engine effectively exhaust gas emissions can be kept low. CO content and idling speed do not need to be adjusted. The need for servicing is small.

The engine control module (ECM) also has an on-board diagnostics system. Signals from sensors, and the operation of the three-way catalytic converter (TWC) and EVAP system are continuously monitored. If possible the engine control module (ECM) will adopt fixed substitute values (limp-home values) to enable the car to be driven if certain signals are faulty or missing.

Substitute values can be adopted for

1. engine coolant temperature (ECT) sensor
2. throttle position (TP) sensor
3. Heated oxygen sensors (HO2S)
4. mass air flow (MAF) sensor

Faults are recorded in the engine control module (ECM) memory. Information can be read-off using the Volvo Scan Tool (ST) connected to the data link connector (DLC) in front of the gear shift and under the coin tray on the center console.

The engine control module (ECM) is housed in a ventilated box in the engine compartment.

Scheme 1065

The engine control module (ECM) receives signals describing running conditions from the following components

1. engine speed and crankshaft position, from the engine speed (RPM) sensor at the flywheel (7/25)
2. working cycle in cylinders, from the camshaft position (CMP) sensor (7/21)
3. engine load, from the mass air flow (MAF) sensor (7/17)
4. height above sea level from the atmospheric pressure sensor (7/95)
5. outside temperature from the outside temperature sensor (7/105), certain markets only
6. engine temperature, from the engine coolant temperature (ECT) sensor (7/16)
7. throttle angle, from the throttle position (TP) sensor (7/54)
8. oxygen content of the exhaust gases upstream of the catalytic converter, from the front heated oxygen sensor (HO2S) (7/15)
9. oxygen content of the exhaust gases downstream of the catalytic converter, from the rear heated oxygen sensor (HO2S) (7/82)
10. engine knock (if present), from the two knock sensors (KS) (7/23 and 7/24)
11. vehicle speed, from the combined instrument panel (5/1)
12. imminent gear shifting, from the automatic transmission control module (TCM) (4/28) (automatics only)
13. gear selector lever in park/neutral or drive positions, from the automatic transmission control module (TCM) (4/28)
14. malfunction indicator lamp (MIL) request from the automatic transmission control module (TCM) (4/28)
15. vertical acceleration of the car from accelerometer (7/79) to determine if the car is being driven on an uneven road, misfire diagnostic
16. if air conditioning (A/C) is selected, from the air conditioning (A/C) system control panel (3/54)
17. air conditioning (A/C) compressor ON signal, from the pressure switch (Pressostat) (7/53)
18. pressure in air conditioning (A/C) system, from the air conditioning (A/C) pressure sensor (7/8)
19. pressure in fuel tank, from fuel tank pressure sensor (7/84), certain markets only

The engine control module (ECM) checks itself and all input and output signals.

See Overview

See Overview

System Overview ME 7.0

See System overview ME 7.0

See System Overview ME 7.0