Fuel injection is not new. Robert Bosch began experimenting with the concept in 1912 and his company developed a direct injection system which enhanced the performance of German military aircraft in time for World War II. Bosch had correctly surmised that a finer pressurized fuel spraywould produce a more combustible mixture of air and fuel thusly increasing power and efficiency.
In 1954, the Mercedes Benz 300 SL used Bosch direct fuel injection, and simultaneously, other companies developed alternative designs. In Britain, Lucas had a mechanical indirect system, which featured a unique shuttle valve metering and distribution unit. ie. the fuel was injected directly into the cylinders during the intake strokes (rather akin to modern diesel injection systems).
A FUEL INJECTOR
However, these systems rested their advantage solely on their better method of fuel delivery and did not combine this as yet with a pre-programmed memory of ideal fuel/air combinations to suit varying demands and conditions.
In the United States, the early Hillborn racing system
was crude but worked well. On the other hand, the 1958 Chrysler Bendix
system was the the most advanced of its time. Here the injectors were triggered
in turn by appropriately timed electrical impulses, the timing being effected
by means of a unit contained within the ignition distributor. Control of
mixture strength was achieved by modulating these impulses so as to cause
them to open the injectors for precisely the required duration. This timing
was accomplished by means of an electronic 'black box' which monitored
information fed into it in accordance with load
(manifold pressure), snap-opening and cold-starting requirements. This was a true electronic fuel injection (EFI) system.
Chrysler offered the Bendix for certain models, but the American infatuation with the traditional carburetor soon had this EFI quietly shelved. It is one of the curiosities of the industry that it reappeared ten years later as the world famous Bosch electronic system!
By 1970, a crowd of different car manufacturers were installing the Bosch K-Jetronic and L-Jetronic systems. These were simple in principle and practice. Airflow, engine temperature and throttle position were measured and quantified into electrical signals which were sent to an analogue control unit, the ECU or 'black box' and this data would then be transformed into the best "solution" and finally sent to the injectors which then opened for the best duration.
To the immediate advantage of more power was added the benefits of less moving parts and a vastly improved ability to deal with extremes in temperature and altitude. No tuning was required and with the electrical values in hand the major components could be repaired by a radio or television repairman. Yet for all this, the public was intimidated by EFI.
"Much of the mystery surrounding fuel injection has been cultivated and nurtured by manufacturers, no doubt to ensure that vehicles so equipped are always returned to franchised dealers for servicing and repairs." This was written by David Hardcastle in 1992 and was true enough then but has become sorely prophetic since.
Originally, the biggest disadvantage with electronic fuel injection systems is that they were expensive.
Electronic fuel injection first appeared on production Rover V8 engines as early as 1977, bound for the emissions-sensitive Australian and Californian markets. Subsequently, it was fitted to TR8s and Rover SD1s sold throughout the entire U.S. However, these early systems were designed specifically to satisfy emission legislation. As noted, EFI has an inherently more efficient combustion which reduces emissions and in the U.S. configuration, airflow was purposefully restricted by a small plenum chamber (the "Federal" plenum), the engine compression was lowered and emissions were constantly monitored by a lambda sensor which signals the ECU that regulatory emission limits are being exceeded. The ECU then reacts accordingly.
It was the Rover SD1 Vitesse, introduced in 1983, that boasted an EFI system designed to increase power output with no compromises. The Vitesse EFI produced 190 bhp from a 3.5 litre engine in the Vitesse Sedan and 205 bhp in its first Morgan installations with the branch heddars and twin exhaust. Though the previous carburetor version of the SD1 was otherwise largely similar, it only produced 155bhp. For the Morgan Plus 8, EFI was an option only for 1984-1986.
Three years after the debut of the Rover Vitesse EFI, Range Rover followed suit and EFI replaced the carbs in the Vogue models in October 1985 and in all V8 4-door models a year after that in November 1986.
There are two basic types of EFI systems fitted to the Rover V8s. Similar in operation, they both use solenoid injectors, one per cylinder operating directly into the inlet ports and a ninth injector into the plenum chamber to aid in cold engine starts. Both systems respond to information from sensors relating to motor temperature, throttle position, air temperature and engine speed...but neither has any control over ignition.
The first system, the
uses the Bosch air-flow
meter with a Lucas
analogue ECU. This
airflow meter has a
hinged flap that measures,
by its position, the flow of
air into the engine, thus
varying the signal sent to
the ECU. The air/fuel mixture
can be altered by turning the
CO2 screw on the air flow
meter and accurate
adjustment requires an
exhaust gas analyzer.
The second system, found in the Range Rover/Discovery only, was introduced to coincide with the "new" 3.9 litre engine in 1988 but was also fitted to some 3.5 litre engines. It incorporates an "hot" wire air metering system designed and manufactured by Hitachi and is matched with a digital Lucas ECU with its fueling information stored on a computer chip/Eprom. This system contains no moving parts and employs two sensor wires, one of which is heated, to measure the air mass as it passes over the wires and into the engine. A voltage signal is then sent to the ECU reflecting the voltage required to maintain the temperature of the heated wire as it is cooled by the air flow.
(Pictures are taken from the top)
The earlier type was also fitted to the first 3.5 EFI
(not catalytic converter equipped) Range Rovers from 1986, is similar (though
not identical) to the system fitted to the SD1 Vitesse, the main difference
being the ECU (electronic control unit). The hotwire type, fitted to the
later Range Rover 3.5, 3.9 & 4.2 vehicles, with or without cat's, despite
appearing quite similar, shares few parts with the "flapper".
Curiously, Land Rover has just recently returned to the Bosch Motronic system and many of the old "flapper" L-Jetronic parts are interchangeable with the newest Motronic.
The hotwire system is less restrictive to the flow of air to the engine and therefore one would presume that it should produce more power. However, this is not so in practice as the increasing exigencies of emission legislation have required more and more compromises to the fueling solutions. Lambda oxygen sensors, catalytic converters and a continuing series of programming prioritize emission issues rather than power. The number of variables that the ECU must deal with has risen from the original 3-4 items to as many as 40-50 in the US version of the V8.
Hardcastle scoffed at a marketing program that instilled
a fear in a customer dealing with EFI systems. EFI principles have not
changed much since then. However, one needs a digital computer to diagnose
a digital computer. Rover/Land Rover conform to the common industry
practice and has priced it's little laptop dignostic computer in the tens
of thousands of dollars. This "closes" the engine off from its owners
and the general auto repair population and forces a reliance on the Land
Rover service network indefinitely. In an environment where you expect
to recylce your vehicle very few years this is not significant. If you
wish to treasure and maintain your vehicle, it is.