fuel supply and carburetor fuel supply and carburetor fuel supply and carburetor fuel supply and carburetor fuel supply and carburetor

1. Lecture # 2
Fuel Supply and Carburetor
1

2. Components of the cylinder charge:
Fresh gas
Fuel can, on the other hand, be injected with the combustion
process and metered precisely to the individual cylinder.
Residual gas (inert gas)
This no longer contains any oxygen and therefore does not
participate in combustion during the following power cycle.
However, it does delay ignition and slows down the course of
combustion, which results in slightly lower efficiency but also in
lower peak pressures and temperatures. In this way, a specifically
used amount of residual gas can reduce the emission of nitrogen
oxides (NOX).
2

3. Gas exchange:
Volumetric efficiency and air consumption
The success of the gas-exchange process is measured in the variables
volumetric efficiency, air consumption and retention rate
Pumping losses
Work is expended in the form of pumping losses or gas-exchange
losses in order to replace the exhaust gas with fresh gas in the gas-
exchange process. (throttling losses and push-out losses)
3

4. Supercharging:
Dynamic supercharging
Supercharging can be achieved simply by taking advantage of the
dynamic effects inside the intake manifold.
Mechanical supercharging
The intake-air density can be further increased by compressors which
are driven mechanically from the engine’s crankshaft.
4

5. Supercharging:
Dynamic supercharging
Supercharging can be achieved simply by taking advantage of the
dynamic effects inside the intake manifold.
Mechanical supercharging
The intake-air density can be further increased by compressors which
are driven mechanically from the engine’s crankshaft.
Exhaust-gas turbocharging
In contrast mechanical supercharging, the compressor of the exhaust-
gas turbocharger is driven by an exhaust-gas turbine located in the
exhaust-gas flow. 5

6. Torque and power:
6

7. Torque and power:
Generation of torque
Relationship between torque and power
The physical quantity torque M is the pro - duct of force F times lever
arm s
7
The engine’s power output P climbs along with increasing torque M
and engine speed n.

8. Torque and power:
8

9. Cylinder-charge control systems
Electronic throttle control (ETC)
9

10. Cylinder-charge control systems
Function and method of operation
10
• The Motronic ECU (2) – ME-Motronic for systems with manifold
injection or DI-Motronic for gasoline direct injection – calculates
the required air mass from the torque to be set and generates the
triggering signals for the electrically actuated throttle valve.
• Using the feedback information from the throttle-valveangle sensor
(3) regarding the current position of the throttle valve, it then
becomes possible to adjust the throttle valve precisely to the
required setting.

11. Cylinder-charge control systems
Function and method of operation
11
• A cruise-control function can also be easily integrated with ETC.
The ECU adjusts the torque in such a way that the vehicle speed
preselected at the control element for cruise control is maintained.
There is no need to press the accelerator pedal.

12. Cylinder-charge control systems
Throttle device
12

13. Cylinder-charge control systems
Throttle device
13
• The use of plastic offers the following advantages over the
aluminum housing:
• Weight saving
• Optimal throttle-valve geometry
• Corrosion resistance
• Low wear
• Less sensitivity to temperature influences
• Less tendency to icing (omission of water heater)

14. Cylinder-charge control systems
Accelerator-pedal sensors
14
• In Motronic systems with Electronic Throttle Control (ETC), the
pedal-travel sensor records the travel or the angular position of the
accelerator pedal. For this purpose, potentiometers are used in
addition to proximity-type sensors.

15. Cylinder-charge control systems
Accelerator-pedal sensors : Potentiometric pedal-travel sensor
15
The engine ECU receives
the measured value picked
off at the potentiometer
wiper as a voltage. The
ECU uses a stored sensor
curve to convert this voltage
into the relative pedal travel
or the angular position of
the accelerator pedal.

16. Cylinder-charge control systems
Accelerator-pedal sensors : Potentiometric pedal-travel sensor
16
A second (redundant) sensor is incorporated for diagnosis purposes and for
use in case of malfunctions. It is a component part of the monitoring system.
One sensor version operates with a second potentiometer, which always
delivers half the voltage of the first potentiometer at all operating points.
Thus, two independent signals are available for fault-detection purposes.
Instead of the second potentiometer, another version uses a low-idle switch,
which signals the idle position to the ECU. The status of this switch and the
potentiometer voltage must be plausible.

17. Cylinder-charge control systems
Accelerator-pedal sensors : Potentiometric pedal-travel sensor
17
For vehicles with automatic transmissions, a further switch can be
incorporated for an electrical kickdown signal. Alternatively, this information
can also be derived from the rate of change of the potentiometer voltage. A
further possibility is to trigger the kickdown function by means of a defined
voltage value of the sensor curve; here, the driver receives feedback on a
jump in force in a mechanical kickdown cell. This is the most frequently used
solution.

18. Cylinder-charge control systems
Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors
18
In this type of sensors, the
magnetic flux of a roughly
semicircular, permanent-
magnetic disk is fed back
via a pole shoe, two further
conductive elements and
the similarly ferromagnetic
shaft to the magnet.

19. Cylinder-charge control systems
Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors
19
Depending upon the angular setting, the flux is led to a greater or lesser degree
through the two conductive elements, in the magnetic path of which a Hall-
effect sensor is also situated. Using this principle, it is possible to achieve a
practically linear characteristic in the measuring range of 90°.

20. Cylinder-charge control systems
Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors
20
The magnet moves around the Hall-
effect sensor in a circular arc. Only
a relatively small section of the
resulting sinusoidal characteristic
curve features good linearity. If the
Hall-effect sensor is located slightly
outside the center of the circular
arc, the characteristic curve
increasingly deviates from the
sinusoidal, and now features a short
measuring range of almost 90°, and
a longer measuring range of more
than 180° with good linearity.

21. Cylinder-charge control systems
Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors
21
A great disadvantage though is the low level of shielding against external fields, as well as
the remaining dependence on the geometric tolerances of the magnetic circuit, and the
intensity fluctuations of the magnetic flux in the permanent magnet as a function of
temperature and age.

22. Cylinder-charge control systems
Accelerator-pedal sensors : Hall-effect angle-of-rotation sensors
22
In this type of Hall-effect angle-of-rotation
sensor, it is not the field strength but rather
the direction of the magnetic field which is
used to generate the output signal. The field
lines are recorded by four radially arranged
measuring elements lying in one plane in the
x- and y-directions. The output signals are
derived in the ASIC from the raw data (cos
and sin signals) using the arctan function. The
sensor is positioned between two magnets to
generate a homogenous magnetic field. The
sensor is therefore insensitive to component
tolerances and temperature-resistant.

23. Cylinder-charge control systems
Accelerator-pedal sensors :
23