Transcript Carburetor - mr. olinyk

It uses pressure from an
electric fuel pump to
spray fuel into the
engine’s intake
manifold
Unlike a carburetor
Pressure not engine
vacuum is used to feed
the engine
This makes it very
efficient
Improved atomization (fuel broken into finer
mist)
Better fuel distribution to each cylinder
Smoother idle (can use a leaner mixture)
Lower emissions (Air fuel ratio)
Increased engine power (precise metering)
Throttle Body
Has an injector
nozzles in a throttle
body assembly on top
of the engine
Fuel is sprayed into
the top center of the
intake manifold
Has fuel injectors in
the intake ports
(air/fuel runners)
Gasoline is sprayed
into each intake port,
towards each intake
valve
Controls the air fuel
mixture more
precisely than T.B.
Sprays fuel into the
engine intake
manifold
Most gasoline
injection systems are
indirect
Forces fuel into the
engine combustion
chamber
All Diesel injection
systems are the direct
type
Simultaneous Injection :
Means all of the injectors open at the same time
Sequential injection: means that the injectors
open one after another
Group Injection: has several but not all of the
injectors opening at the same time( V8 might
have 4 injectors open at one time)
Fuel Delivery:
1.
Electric fuel pump
2.
Fuel filter
3.
Pressure regulator
4.
Fuel injectors
5.
Connecting lines and
hoses
Consists of an
1.
Air filter
2.
Throttle valve
3.
Sensors
4.
Connecting duct work
Air enters the duct work
The air filter traps
particles
it’s then routed to the
throttle body
The throttle body
(multiport injection )
The air goes past the
throttle plate and flows
into the intake runners
The runners route the
air into each cylinder
head intake port
2.
What are the two gasoline fuel injection
systems ?
What are the two ways fuel is injected into the
combustion chamber (hint all diesel are this
way)?
3.
What are the injector opening times?
4.
Name the parts that make up the Fuel delivery
system?
1.
An EFI sensor system monitors engine
operating conditions and reports this
information to the engine control module
An engine sensor is an electrical device that
changes circuit resistance or voltage with a
change in a condition such as temperature,
pressure or position
INPUTS
1.
2.
3.
4.
5.
Oxygen sensor
Engine coolant temp
sensor
Throttle position sensor
M.A.P
Knock sensor
OUTPUTS
1.
2.
3.
4.
Fuel pump relay
EGR solenoid
Fuel injectors
Idle air control
(I.A.C.)motor
Power train Control
Module is the brain of
an electronic fuel
injection system it’s a
preprogrammed
microcomputer.
Input sensors feed
information to the
P.C.M. the P.C.M. uses
this data to operate the
Output sensors
It measures the
oxygen content in the
engine’s exhaust
system as a means of
checking combustion
efficiency
Vehicles that are OBD
2 uses at least two O2
sensors Pre and Post
catalytic converter
The voltage output (or
resistance) of the 02
varies with changes in
the oxygen content of
the exhaust
Lean mixture makes the
sensor output voltage
decrease e.g. .1 volt
A decrease in oxygen
from a rich mixture
causes the sensor
output to increase e.g. .9
Volt
OPEN LOOP
The P.C.M. does not use
engine exhaust gas
content as a main
indicator of the air/fuel
mixture
Instead the system
operates on information
stored in the P.C.M
CLOSED LOOP
The computer is using
information from the
oxygen sensor and
other sensors
This information forms
an imaginary loop from
the P.C.M. to the fuel
system to the exhaust
system and back to the
P.C.M.
Manifold absolute
pressure sensor it
measures the pressure
or vacuum inside the
engine intake
manifold
Manifold pressure is a
good indicator of
engine load
T.P. sensor is a
variable resistor
connected to the
throttle plate shaft
When the throttle
opens or closes, the
sensor changes
resistance and signals
the computer
Monitors the operating
temp. of the engine
Its mounted so it is
exposed to engine
coolant
The P.C.M. uses this
information to adjust
air/fuel ratio
1.
What is an engine sensor?
2.
What does P.C.M. stand for?
3.
What job does an O2 sensor perform?
4.
What is open loop?
5.
What does M.A.P sensor stand for
Used to measure the
amount of outside air
entering the engine
This helps the E.C.M
determine how much
fuel is needed
Piezoelectric sensor
that detects engine
pinging, preignition
or detonation so the
computer can retard
timing
Used to detect engine
speed
It allows the ECM to
change injector timing
and duration with
changes in engine
RPM
Higher engine RPM
more fuel
Digital signal
Are on /off signals
An example of a
sensor providing a
digital signal is the
crank shaft position
Voltage goes from
max. to min. like a
light switch
Analog Signal
Changes in strength to
let the computer
know about change in
a condition
e.g. Coolant temp
sensor it’s a variable
resistance
The injector sprays
fuel into the top of the
throttle body air horn
The fuel spray mixes
with the incoming air
The mixture is then
pulled into the engine
by intake manifold
vacuum
Typically consists of:
Throttle body housingthis is the metal
casting that holds the
subassemblies
Fuel Injector- a
solenoid operated fuel
valve
Fuel Regulator-a
spring loaded bypass
valve that maintains
constant pressure at
the injector
Throttle position sensor
a variable resistor that
reads throttle plate
position
Consists of a fuel valve,
diaphragm, and spring
When fuel pressure is low
(starting engine) The
spring holds the fuel
valve closed. This
causes pressure to build
When a preset pressure
is reached the spring is
over come
1.
What are the two electrical signals sensors
produce?
2.
How does a knock sensor work?
3.
What does a crankshaft position sensor do?
4.
What does T.B.I stand for?
Idle Air Control Valve
It’s a solenoid or a
stepper motor
controlling the air
bypass around the
throttle plates
Its computer controlled
Its used on both
multiport and TBI
injection
Uses a computer, engine
sensors and one
solenoid injector for
each cylinder
This is the most common
system used on late
model vehicles
The assemble contains
the throttle plates,
throttle position
sensor
Its main function is to
control airflow into
the engine
Is mounted in the fuel
rail after the injectors
performs the same
function as Throttle
body injection
It differs by using
engine vacuum to
control it rather then
spring tension
Reading O2 sensor
Normally O2 sensors
are designed to last
80,000km however,
it’s life can be
shortened by
contamination
Using a Noid light to
check the harness side
of the injector
They are designed to
check for normal
digital current pulses
To test the injector do
a balance test
Injector 1. FAIR - but
weak
Injector 2. BAD - split
spray pattern
Injector 3. BAD - split
spray pattern
Injector 4. BAD - jetting
on left side
Injector 5. GOOD
Injector 6. BAD feathering at top of spray
Used to communicate
and retrieve trouble
codes from the
vehicles computer
It also displays circuit
and sensor values, run
tests and give helpful
hints for finding
problems
If the onboard
computer finds any
abnormal values it
will store a trouble
code and light a
malfunction indicator
light on the
instrument panel
Some vehicles can have
6 more computers
O.B.D. 1 Early on board
diagnostic system could
only check a limited
number of items 19861995
O.B.D 2 designed to more
efficiently monitor the
condition uses greater
processing speed more
memory and more
complex tasks 1996present
C.A.N. O.B.D Controller
Area Networking all
2008 and newer vehicles
CAN-equipped vehicle is
shared over a serial data
bus. The bus is the
circuit that carries all
the electronic chatter
between modules
1.
What is Multiport injection?
2.
What controls the fuel regulator on multiport
injection?
3.
What two tools can we use to check fuel
injectors?
4.
What are the OBD systems on vehicles?
A carburetor is basically a
device that mixes air
and fuel in the correct
proportions (amounts)
for efficient combustion
When the engine is
running the intake
stroke creates suction in
the intake manifold
Air rushes through the
carb. were fuel is mixed
with it
Body-Is cast metal
housing for the
components It has
cast and drilled
passages for air and
fuel
Air Horn-also called
barrel routes outside
air into the engine
intake manifold
Throttle Valve-is a
butterfly valve located
in the air horn when its
closed it restricts air
flow into the engine
Venturi- produces suction
to pull fuel out of the
main discharge tube
The narrow air way
increases air velocity
Main Discharge tubealso called main fuel
nozzle it’s passages
in the main body
that connects the
fuel bowl to the
venturi
Fuel bowl-holds a
supply of fuel that is
not under fuel pump
pressure
Is a network of passages
and related parts that
help control the air/fuel
ratio under a specific
engine operating
condition
Each circuit supplies a
predetermined air/fuel
mixture as the
temperature, speed and
engine load change
Must be capable of
providing varying
air/fuel ratios:
8:1 cold start
16:1 idling
15:1 part throttle
13:1 full acceleration
18:1 cruising speeds
There are 7 basic carb.
circuits
Must maintain the correct
level of fuel in the
carburetor bowl
The float system prevents
the fuel pump from
forcing too much fuel in
the bowl
The bowl is also vented to
prevent psi and vacuum
buildup
Needle and seat works
with the float to control
the flow
Provides the engine’s
air/fuel mixture at
speeds below 800
RPM or 20 KM/h
The throttle is almost
closed there is no
venturi action instead
high intake vacuum
below the throttle
plates feed fuel into
the barrel
Feeds more fuel into the
air horn when the
throttle plates are
partially open.
Functions above 800
RPM
Without this circuit the
mixture would
become too lean off
idle
Provides extra fuel when
changing from the
idle circuit to high
speed circuit
The acceleration circuit
squirts a stream of
fuel into the barrel
when the accelerator
is pressed
Supplies the engine
air/fuel at cruising
speeds It begins to
function when the
throttle plates are
open enough for
venturi action
Provides the most
efficient fuel/air ratio
The jet hole size
determines how much
fuel flows through the
circuit
Enriches the high speed circuit
when needed
Power valve :
when the engine is at cruise
speed the manifold
vacuum is high the vacuum
acts on the diaphragm and
pulls the valve closed
When the throttle plates are
swung open engine
manifold vacuum drops off
the spring in the power
valve opens and fuel flows
Designed to provide an
extremely rich air/fuel
mixture to aid in cold
starts
Is a butterfly valve located
at the top of the
carburetor air horn
when its closed it blocks
normal air flow causing
high intake vacuum to
form below the choke
plate pulling fuel from
the main discharge
tube
F
I
L
M
P
A
C
float Circuit
Idle circuit
Low speed
Main metering
Power circuit
Acceleration circuit
Choke circuit
Are the components that
operate under normal
driving conditions
In a 4 barrel carburetor
the primary consists
of the 2 front throttle
plates and related
components
Consists of the
components or
circuits that function
under high engine
power output
conditions
They only function
when more power is
needed
Generally carburetor
Size is stated in CFM
(cubic feet of air per
minute)
This is the amount of
air that can flow
through the
carburetor at wide
open throttle
•
•
A slide-type, has a cylinder-shaped slide that moves in
and out of the air horn to help control fuel and airflow.
The piston sliding in and out regulates the size of the
venturi. These are commonly used on motorcycles.
A carburetor is
basically a device for
mixing air and fuel in
correct amounts
The float system must
maintain the correct
level in the bowl
Low speed circuit feeds
more fuel into the barrel
when the throttle plates
are partially open
The main metering circuit
supplies the engine’s
air/fuel mixture at
normal cruising speeds
The power circuit provides
a means of enriching
the fuel mixture for
high speed
The choke circuit is
designed to supply an
extremely rich air/fuel
ratio to aid in cold starts