Ecu cI -fuel injection

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHATRONICS ENGINEERING
Session: Electronic controlled fuel
injection system for CI - Engine
11/24/2020 16MT407 - Theory of Automobile Engineering 1
MODULE 1

SESSION OBJECTIVES
 On the completion of this session, the students might
be able to understand,
 How the electronics system plays a role in CI
Engine fuel supply system

Topics
 Principle of CI – Engine fuel injection
 Types of Electronic controlled Fuel injection
system in CI – Engine
 Individual pump fuel injection system
 Common Rail Fuel injection system
 Unit Fuel injection system
 Distributor type fuel injection system.

PRINCIPLE OF CI - ENGINE
 IN SI-Engine, The air fuel mixture sends to
engine in proper ratio for combustion.
 IN CI – Engine, Pure air is drawn into
engine cylinder from atmosphere during
suction & Compression stroke.
 During compression the air attains 500oc to
600oc.
 This enough to ignite the fuel during
power stroke.

PRINCIPLE OF CI - ENGINE
Why Diesel engine are CI Engine?
 Thus, it can be said that during
compression of the air in the engine
cylinder, the temperature of air goes up, so
that when the fuel, in the form of a spray
comes in contact with hot air, it ignites and
no other external means of ignition is
required.

CLASSIFICATION IN CI – ENGINE INJECTION SYSTEM
CI – Engine Fuel Injection
Air Injection System Solid Injection system

Air Injection System :
 Fuel is forced by high
pressure compressed air
 By varying the air pressure,
the rate of fuel admission can
controlled.
 Metering & Pumping of fuel to
fuel valve is done by
camshaft driven fuel pump
 The fuel valve is opened by
mechanical linkage operated
by the camshaft, which
controls the timing of
injection

 The fuel valve is also
connected to a high pressure
air line fed by a multi stage
compressor which supplies
air at a pressure of about 60
bar to 70 bar.

Advantage
 Better atomization &
Distribution of fuel
 Heavy & Viscous fuels,
which are cheaper can also
be injected

Disadvantage
 Requires high pressure
multistage compression
 Which utilize the 10-14% of
Engine Power
 Fuel valve required separate
linkage mechanism to
control fuel injection timing.

Solid Injection System :
 In this system, only the liquid fuel under high pressure is directly injected into
the combustion chamber of the engine cylinder. ( No high pressure
compressed air is required)

Solid Injection System
1. Individual pump & Injector
2. Unit Injector System
3. Common rail System
4. Distributor System

Solid Injection System: Advantage
 Simple in Construction
 Light in Weight
 Not so Expensive
 Higher atomization is achieved.

Individual pump & Injector:
 In this system, each cylinder is
provided with one pump & one
injector.
 Also in this system a separate
metering & Compression pump
is provided for each cylinder.
 The pump may arrange close to
cylinder as shown in Fig.

Individual pump & Injector:
 Or May arrange as a cluster
form by shown in image.
 In high pressure pump, plunger
is actuated by a cam & Produces
the fuel pressure necessary to
open the injector valve at the
correct time.
 Plunger actuation determines
the amount of fuel injection.

Common Rail Fuel Injection: Components

Common Rail Fuel Injection:
 The fuel injector gets high pressure fuel from, High pressure, constant stroke,
& Constant Delivery fuel pump.
 The rail is a high pressure accumulator & Common for all cylinder.
 From the common rail the fuel is transferred through rigid pipes to each of
the fuel injector, which injects correct amount of fuel into combustion
chamber.
 Fuel injector operates by either mechanically/Electronically.
 Electronic controlled obtained a different spray pattern for more powerful
explosion & Perfect combustion.
 The excess fuel is returned to the fuel tank from the relief valve.

Modern Common Rail Fuel Injection system:

Working of Bosch Common rail Fuel injection: (Gen 2)

High pressure Fuel pump:

Transfer pump:
 Transfer Pump supplies fuel from
the fuel tank to the pumping
chamber of the high pressure
pump

Fuel metering control valve:
 Fuel metering valve regulates
the fuel intake volume to the
pumping chambers of the high
pressure pump.

Fuel metering control valve: Working

Fuel metering control valve: Diagnosis
 Solenoid circuit monitored by Engine ECM.
 If an open or short circuit is detected
 Engine stops or will not start
 DTC stored (Diagnostic trouble code) & MIL
Illuminated (Malfunction Indication Lamp)
 Mechanical failure of the metering control valves does
not necessarily prevent the engine from starting.
 Mechanical faults can cause DTC’s relating to
positive or negative rail pressure deviation.

High Pressure Accumulator: Common Rail
 Fuel is supplied to the common rail at high pressure from high pressure pump
 The rail stores the fuel and distributes it to the individual injectors.
 It also damps pressure vibration caused by the high pressure pump and
injection process
 Typical volume of fuel in common rail: 16 – 20CM3

High Pressure Accumulator: Common Rail
 Typical fuel rail pressure at Engine Idling & Running temperature condition,
varies from 300 to 400 bar
 Maximum possible fuel rail pressure 1600 to 2000 bar

Fuel rail pressure sensor:

Fuel rail pressure sensor:
 Monitors fuel pressure in common rail
 Piezo resistive type sensor.
 The resistive value of the sensor creates the change in voltage on the signal
wire relative to the fuel rail pressure.

Fuel rail pressure sensor: Working
ECM Applies 5 V to Sensor
Sensor Output for pressure variation in accumulator

Rail pressure limiter valve:

Fuel rail pressure control valve solenoid:

Fuel Injector:
 The fuel injector are controlled by either solenoid or Piezo actuator
 They are energized by sequentially by the engine ECM
 Multiple injection processes per cylinder combustion are possible

Fuel Injector: Purpose of multiple injection per cycle
 Common rail has multiple injection per work cycle.
 Pre injection (Pilot injection) for quiet engine running
 Main injection for ideal power development
 Secondary injection for reduced emission

Fuel Injector: Components

Fuel Injector: Working –Step 1

Fuel Injector: Working – Step 2

Fuel Injector: on 3rd Generation CMR

Common rail Fuel injection: Advantage
 Higher injection pressure & finer atomization of fuel is achieved.
 Multiple injection per cylinder combustion are possible
 Reduction of over all exhaust emission
 Fuel efficiency gets improved
 Higher performance

Electronically controlled Unit injector system or Pump
Duse
 Advanced than common rail fuel injection system
 VW groups vehicle normally used this system in the name
of TDI – Turbocharged Direct injection
Construction :
 Each cylinder will have an high pressure pump & Fuel
Injector
 A separate cam mechanism which operate the high
pressure pump

Electronically controlled Unit injector system or Pump
Duse
How it works?
 Solenoid/Electronic controlled ensure the precise & High
pressure fuel delivery.
Advantage :
 Better atomization of fuel
 Better combustion
 Reduced Emission
 Better Mileage

Electronically controlled Unit injector system or Pump Duse
How it works? – Sequence of Events
 Filling the high pressure chamber
 Pre-Injection cycle
 Post injection cycle or Main injection

Electronically controlled
Unit injector system or
Pump Duse
How it works? – 1. Filling
the High pressure chamber
 Rotation of injection cam
pump piston is pulled up.
 High pressure chamber
gets filled by fuel
 No solenoid actuation
during this period

Pump Duse
How it works? – 2.
Beginning of Pre Injection
Cycle:
 Solenoid is energized
 Due to the pressure
difference in the chamber,
the injector spring is lifted
and the pre – injection is
done

Pump Duse
How it works? – 3. Post
injector or main injection
cycle:
 The position of the
solenoid is changed and its
made open for a longer
time

Electronically controlled distributor type diesel fuel injection
 The rotary distributor type of pump pressurizes & distributes fuel for each
cylinder.
 The injector & Pump are controlled by ECU unit.

END

Ecu cI -fuel injection

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