Fuel injection technology for automotive petrol engines
Jetronic
is a trade name of a
manifold injection
technology for automotive
petrol engines
, developed and marketed by
Robert Bosch GmbH
from the 1960s onwards. Bosch licensed the concept to many
automobile manufacturers
. There are several variations of the technology offering technological development and refinement.
D-Jetronic (1967?1979)
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Analogue fuel injection, 'D' is from
German
:
"Druck"
meaning pressure. Inlet
manifold vacuum
is measured using a pressure sensor located in, or connected to the
intake manifold
, in order to calculate the duration of fuel injection pulses. Originally, this system was called Jetronic, but the name D-Jetronic was later created as a
retronym
to distinguish it from subsequent Jetronic iterations.
D-Jetronic was essentially a further refinement of the
Electrojector
fuel delivery system developed by the
Bendix Corporation
in the late 1950s. Rather than choosing to eradicate the various reliability issues with the Electrojector system, Bendix instead licensed the design to Bosch. With the role of the Bendix system being largely forgotten D-Jetronic became known as the first widely successful precursor of modern electronic common rail systems; it had constant pressure fuel delivery to the injectors and pulsed injections, albeit grouped (2 groups of injectors pulsed together) rather than sequential (individual injector pulses) as on later systems.
As in the Electrojector system, D-Jetronic used
analogue
circuitry, with no
microprocessor
nor
digital logic
, the
ECU
used about 25
transistors
to perform all of the processing. Two important factors that led to the ultimate failure of the Electrojector system: the use of paper-wrapped capacitors unsuited to heat-cycling and amplitude modulation (tv/ham radio) signals to control the injectors were superseded. The still present lack of processing power and the unavailability of solid-state sensors meant that the vacuum sensor was a rather expensive precision instrument, rather like a
barometer
, with brass bellows inside to measure the manifold pressure.
Although conceptually similar to most later systems with individual electrically controlled injectors per cylinder, and
pulse-width modulated
fuel delivery, the fuel pressure was not modulated by manifold pressure, and the injectors were fired only once per 2 revolutions on the engine (with half of the injectors being fired each revolution).
The system was last used (with a
Lucas
designed timing mechanism and Lucas labels super-imposed on some components) on the Jaguar V12 engine (
XJ12
and
XJ-S
) from 1975 until 1979.
K-Jetronic (1973?1994)
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Mechanical fuel injection, 'K' stands for
German
:
"Kontinuierlich"
, meaning
continuous
. Commonly called 'Continuous Injection System (CIS) in the USA. K-Jetronic is different from pulsed injection systems in that the fuel flows continuously from all injectors, while the
fuel pump
pressurises the fuel up to approximately 5
bar
(73.5
psi
). The volume of air taken in by the engine is measured to determine the amount of fuel to inject. This system has no
lambda
loop or lambda control. K-Jetronic debuted in the 1973.5
Porsche 911
T in January 1973, and was later installed into a number of
Porsche
,
Volkswagen
,
Audi
,
BMW
,
Mercedes-Benz
,
Rolls-Royce
,
Bentley
,
Lotus
,
Ferrari
,
Peugeot
,
Nissan
,
Renault
,
Volvo
,
Saab
,
TVR
and
Ford
automobiles. The final car to use K-Jetronic was the 1994 Porsche 911 Turbo 3.6.
Fuel is pumped from the tank to a large control valve called a
fuel distributor
, which divides the single fuel supply line from the tank into smaller lines, one for each injector. The fuel distributor is mounted atop a control vane through which all intake air must pass, and the system works by varying fuel volume supplied to the injectors based on the angle of a
moving vane
in the
air flow meter
, which in turn is determined by the volume of air passing the vane, and by the control pressure. The control pressure is regulated with a mechanical device called the control pressure regulator (CPR) or the warm-up regulator (WUR). Depending on the model, the CPR may be used to compensate for altitude, full load, and/or a cold engine. The injectors are simple spring-loaded
check valves
with nozzles; once fuel system pressure becomes high enough to overcome the counterspring, the injectors begin spraying.
K-Jetronic (Lambda)
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First introduced in the Volvo 265 in 1976 and later used in the
DMC DeLorean
in 1981. A variant of
K-Jetronic
with
closed-loop
lambda
control, also named Ku-Jetronic, the letter u denominating USA. The system was developed to comply with
U.S.A.
state
of
California's
California Air Resources Board
exhaust emission regulations, and later replaced by
KE-Jetronic
.
KE-Jetronic (1985?1993)
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Electronically controlled mechanical fuel injection. The
engine control unit
(ECU) may be either analog or digital, and the system may or may not have closed-loop lambda control. The system is based on the K-Jetronic mechanical system, with the addition of an electro-hydraulic actuator, essentially a fuel injector inline with the fuel return. Instead of injecting fuel into the intake, this injector allows fuel to bypass the fuel distributor, which varies the fuel pressure supplied to the mechanical injection components based on several inputs (engine speed, air pressure, coolant temperature, throttle position, lambda etc.) via the ECU. With the electronics disconnected, this system will operate as a K-Jetronic system.
[1]
Commonly known as 'CIS-E' in the USA. The later KE3 (CIS-E III) variant features
knock
sensing capabilities.
L-Jetronic (1974?1989)
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Analog fuel injection. L-Jetronic was often called Air-Flow Controlled (AFC) injection to further separate it from the pressure-controlled D-Jetronic — with the 'L' in its name derived from
German
:
luft
, meaning 'air'. In the system, air flow into the engine is measured by a moving vane (indicating engine load) known as the
volume air flow sensor
(VAF) — referred to in German documentation as the
LuftMengenMesser
or LMM. L-Jetronic used custom-designed
integrated circuits
, resulting in a simpler and more reliable
engine control unit
(ECU) than the D-Jetronic's.
[2]
L-Jetronic was used heavily in 1980s-era
European
cars,
[3]
as well as
BMW K-Series
motorcycles. Licensing some of Bosch's L-Jetronic concepts and technologies,
Lucas
,
Hitachi Automotive Products
,
NipponDenso
, and others produced similar fuel injection systems for Asian car manufacturers. L-Jetronic manufactured under license by
Japan Electronic Control Systems
was fitted to the
1980 Kawasaki Z1000-H1
, the world's first production fuel injected motorcycle. Despite physical similarity between L-Jetronic components and those produced under license by other manufacturers, the non-Bosch systems should not be called L-Jetronic, and the parts are usually incompatible.
LE1-Jetronic, LE2-Jetronic, LE3-Jetronic (1981?1991)
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This is a simplified and more modern variant of
L-Jetronic
. The ECU was much cheaper to produce due to more modern components, and was more standardised than the L-Jetronic ECUs. As per L-Jetronic, a vane-type airflow sensor is used.
[4]
Compared with L-Jetronic, the fuel injectors used by LE-Jetronic have a higher impedance.
[5]
Three variants of LE-Jetronic exist: LE1, the initial version. LE2 (1984?), featured cold start functionality integrated in the ECU, which does not require the cold start injector and thermo time switch used by older systems. LE3 (1989?), featuring miniaturised ECU with hybrid technology, integrated into the junction box of the mass airflow meter.
LU1-Jetronic, LU2-Jetronic (1983?1991)
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The same as
LE1-Jetronic
and
LE2-Jetronic
respectively, but with closed-loop lambda control. Initially designed for the US market.
LH-Jetronic (1982?1998)
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Digital fuel injection, introduced for California bound 1982
Volvo 240
models. The 'LH' stands for
German
:
"Luftmasse-Hitzdraht"
- the
hotwire anemometer
technology used to determine the
mass
of air into the engine. This
air mass meter
is called HLM2 (
Hitzdrahtluftmassenmesser
2) by Bosch. The LH-Jetronic was mostly used by
Scandinavian
car manufacturers, and by sports and luxury cars produced in small quantities, such as
Porsche 928
. The most common variants are LH 2.2, which uses an
Intel
8049 (
MCS-48
) microcontroller, and usually a 4
kB
programme memory, and LH 2.4, which uses a
Siemens
80535 microcontroller (a variant of Intel's 8051/
MCS-51
architecture) and 32 kB programme memory based on the 27C256 chip. LH-Jetronic 2.4 has adaptive lambda control, and support for a variety of advanced features; including fuel enrichment based on
exhaust gas
temperature (ex.
Volvo B204GT/B204FT engines
). Some later (post-1995) versions contain hardware support for first generation diagnostics according to
ISO 9141
(a.k.a.
OBD-II
) and immobiliser functions.
[
citation needed
]
Mono-Jetronic (1988?1995)
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Digital fuel injection. This system features one centrally positioned fuel injection nozzle. In the US, this kind of
single-point
injection was marketed as 'throttle body injection' (TBI, by GM), or 'central fuel injection' (CFI, by Ford).
Mono-Jetronic is different from all other known single-point systems, in that it only relies on a throttle position sensor for judging the engine load. There are no sensors for air flow, or intake manifold vacuum. Mono-Jetronic always had adaptive closed-loop lambda control, and due to the simple engine load sensing, it is heavily dependent on the lambda sensor for correct functioning.
The ECU uses an
Intel 8051
microcontroller
, usually with 16 KB of programme memory and without advanced
on-board diagnostics
(OBD-II became a requirement in model-year 1996.)
See also
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References
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]
- ^
Robert Bosch GmbH (1985). Electronically Controlled Gasoline Fuel-Injected System with Lambda Closed-Loop Control - KE-Jetronic.
- ^
Baggeroer, Artgur B. L-Jetronic fuel injection. July 1985. General OneFile. Web. 23 July 2012.
- ^
Lee Thompson, John De Armond (22 June 1993).
"L-Jetronic"
(archived
usenet
message)
. Retrieved
17 November
2009
.
- ^
"LE-Jetronic"
.
www.bosch-automotive.com
. Retrieved
23 September
2017
.
- ^
"About Opel fuel injection systems"
.
www.users.telenet.be
. Retrieved
23 September
2017
.
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