Electronic control systems for diesel injectionElectronic control systems for diesel injection • Mechanical control systems have proven their reliability and Mechanical control systems have proven their reliability and

precision for many yearsprecision for many years. . • The first electronic diesel control (EDC) was used in 1983 with The first electronic diesel control (EDC) was used in 1983 with

distributor pumps which used electronic controls: distributor pumps which used electronic controls: • It is possible to adjust the start of injection more accurately and It is possible to adjust the start of injection more accurately and

flexibly according to the engine requirements.flexibly according to the engine requirements.• Electronic control systems improves fuel economy and reduce the Electronic control systems improves fuel economy and reduce the

amount of pollutants in the exhaust. amount of pollutants in the exhaust. In overall the electronic control systems has provided greater In overall the electronic control systems has provided greater

degree of flexibility and accurate control in many key parameters degree of flexibility and accurate control in many key parameters like;like;

Injection quantity Injection quantity Injection durationInjection duration Injection beginning Injection beginning Idling speed and many others. Idling speed and many others.

The diesel fuel injection system consists of an injection pump, delivery pipes and fuel injector nozzles

The fuel injection process controls only four basic functions: 1. Timing and duration of injection 2. Injection rate 3. Injection quantity 4. Spray quality

o Camshaft drives a single-cylinder injection pump

o The injection nozzle has several holes through which the fuel sprays into the cylinder.

o A spring-loaded injection needle keeps the injection valve closed until the pressure in the injector volume, acting on parts of the needle surface, overcomes the spring force and opens the valve.

Types of Injection System

Diesel injection systems - two types Air injection system ( 60-70 bar) Air less injection system- solid injection for high pressure

system

Air less injection system- solid injection• Individual pump & injector or jerk pump system• Common rail system • Distributor system

Common-Rail Direct Injection (CRDI) The manner in which fuel is injected into the cylinder determines

the engine's torque, fuel consumption, emission and noise level.Critical factors which influence the Injections are; Injection pressure. Shape of injector and no of holes No. of injections Imp. components are:: High Pressure Pump- For generating high pressure fuel in the rail. Rail- Reservoir of high pressure fuel. Injectors- Inject the required amount of fuel into the combustion

chamber. Electronic Control Unit (ECU)- Acts as a control center with inputs

from a number of sensors.

Common-Rail Direct Injection (CRDI)

Common-Rail Direct Injection (CRDI)

Requirement for CRDI: • Common rail with electronic control unit eliminate the problems

associated with interconnecting pipes in traditional pump-line-injector systems.

• CRDI have scope for pilot injection and more desirable injection pressure characteristics.

Pilot injection means:: It is an additional small amount of fuel injection before the power producing main fuel pulse.

• Modern engines use a pilot injection before the power producing main fuel pulse. This smoothens the pressure spike and dramatically reduces the engine noise..

• Pilot injection also reduces peak combustion temperature which helps to reduce NOx emissions drastically.

• It means it controls the amount of fuel injected during the ignition delay period

• In the Common Rail System, the two functions, namely pressure generation and injection are performed separately.

• Firstly pressure generation and storing the fuel under high pressure in a central rail.

• Secondly, delivering the fuel to the individual cylinders through the electronically-controlled injectors on demand.

• High-pressure pump generates in an rail - a pressure of up to 1,600 bar.

• Pump runs independently of the engine speed and the quantity of fuel injected.

• Whenever the injector opens, the high-pressure fuel in the rail is injected into combustion chamber quickly.

• Here injector acts as a valve rather than a pressure generator.

Common-Rail Direct Injection (CRDI) –ECU

• The ECU controls all the injection parameters such as the pressure in the rail, the timing and duration of injection, as well as performing other engine functions.

• This ensures that incredibly high injection pressures are available at all times, even at low engine speeds.

• The electronic control unit is able to collect different data from the engine and operating conditions with sensors

Common-Rail Direct Injection (CRDI)