Engine Management System

Question 1

What does the EMS enable?

Answer 1

Fully control of engine through varying speeds and loads

Maintain current manufacturers emission regulations

Communication between other systems

Stopped under certain safety conditions

Question 2

What is the EMS structure ?

Answer 2

Engine sensors that send ecu inputs to the ECU, which send ecu outputs to the engine actuators

Question 3

What is ROM?

Answer 3

Read only memory

Pre programmed by the manufacturer and cannot be altered unless a re map is carried out

Question 4

What is RAM

Answer 4

Random access memory

Variable information about the engine, it changes all the time and is compared to the rom in order to decide what action to take

Question 5

What are sensors ?

Answer 5

Turns mechanical movements into electrical signals for the ÉCU to read

Question 6

What are actuators ?

Answer 6

Turns electrical signals from ECU into mechanical movement

Question 7

What is the lambda sensor ?

Answer 7

Measure oxygen in exhaust gases

Measure the content before the catalytic converter and after

Question 8

Where is the closed loop signal being used?

Answer 8

Engine idling 
Cruising speed (constant speed)

Question 9

Where is open loop scenarios being used?

Answer 9

Acceleration
Deceleration (engine braking)
Cold start

Question 10

What is the throttle position sensor?

Answer 10

Informs the ECU of the position of the throttle

Can be a potentiometer or contact type switch

Question 11

What does an air flow sensor do?

Answer 11

Informs the ECU of the amount of air entering the system

Question 12

What are the 2 types of air flow sensors?

Answer 12

Mechanical type- measures the amount of air by VOLUME

Electronic type- Measures amount of air by MASS

Question 13

How does the mechanical air flow sensor work?

Answer 13

Air deflects the flap and rotates the spindle which turns a wiper on the potentiometer- change in resistance

Adjust fuel to maintain correct ratio

Question 14

What is the bypass port used for on an airflow operation ?

Answer 14

Allow air flow when idling

Question 15

How does the electrical airflow sensor work?

Answer 15

ECU applies a small current to a wire , the cooling effect of the air causes the resistance to change in the wire, this determines the air temperature

The amount of current can determine whats happening to the air

Question 16

What is a MAP sensor ?

Answer 16

Measure the amount of air entering the intake manifold in order to tell the ECU how much load is on the engine

Does this by measuring the vacuum created by acceleration - depression pulls diaphragm up causing the wiper to change the resistance

Question 17

What is the crank angle sensor ?

Answer 17

Informs the ECU of the position and rotational speed of the crankshaft

RPM

Question 18

Where can the CAS be located ?

Answer 18

Near the front pulley or on the bell housing

Question 19

How does the CAS operate?

Answer 19

When the reluctor tooth is not level , voltage is produced which is detected by the ECU, when the tooth is level no voltage is lost

The pulses are counted per minute and this calculates the rpm

Question 20

What is a knock sensor ?

Answer 20

Detect pressure changes in the cylinder block due to pre ignition and pre detonation

Question 21

How does the knocking sensor work?

Answer 21

Voltage fed to piezoelectric crystal

Detonation occurs

This bends with shock wave and changes the resistance and the voltage changes

It uses this to retard the ignition timing or injection

Question 22

What is the fuel injector valve?

Answer 22

Control the flow of fuel into the engine

Uses a solenoid, which produces a magnetic field and this attracts the nozzle causing the fuel to be injected and when the voltage is removed the nozzle returns to its seat