Fuel injection is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s.

A fuel injection system is designed and calibrated specifically for the type(s) of fuel it will handle. Most fuel injection systems are for gasoline or diesel applications. With the advent of electronic fuel injection (EFI), the diesel and gasoline hardware has become similar. EFI's programmable firmware has permitted common hardware to be used with different fuels.

Carburetors were the predominant method used to meter fuel on gasoline engines before the widespread use of fuel injection. A variety of injection systems have existed since the earliest usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on low pressure created by intake air rushing through it to add the fuel to the airstream.

The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from a pump or a pressure container farther back in the fuel supply.

Objectives

The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system will be optimized. There are several competing objectives such as:

power output

fuel efficiency

emissions performance

ability to accommodate alternative fuels

reliability

driveability and smooth operation

initial cost

maintenance cost

diagnostic capability

range of environmental operation

Engine tuning

Certain combinations of these goals are conflicting, and it is impractical for a single engine control system to fully optimize all criteria simultaneously. In practice, automotive engineers strive to best satisfy a customer's needs competitively. The modern digital electronic fuel injection system is far more capable at optimizing these competing objectives consistently than a carburetor. Carburetors have the potential to atomize fuel better (see Pogue and Allen Caggiano patents).

Benefits

Engine operation

Operational benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions, easier and more dependable engine starting, better operation at extremely high or low ambient temperatures, increased maintenance intervals, and increased fuel efficiency. On a more basic level, fuel injection does away with the choke which on carburetor-equipped vehicles must be operated when starting the engine from cold and then adjusted as the engine warms up.

An engine's air/fuel ratio must be precisely controlled under all operating conditions to achieve the desired engine performance, emissions, driveability, and fuel economy. Modern electronic fuel-injection systems meter fuel very accurately, and use closed loop fuel-injection quantity-control based on a variety of feedback signals from an oxygen sensor, a mass airflow (MAF) or manifold absolute pressure (MAP) sensor, a throttle position (TPS), and at least one sensor on the crankshaft and/or camshaft(s) to monitor the engine's rotational position. Fuel injection systems can react rapidly to changing inputs such as sudden throttle movements, and control the amount of fuel injected to match the engine's dynamic needs across a wide range of operating conditions such as engine load, ambient air temperature, engine temperature, fuel octane level, and atmospheric pressure.

A multipoint fuel injection system generally delivers a more accurate and equal mass of fuel to each cylinder than can a carburetor, thus improving the cylinder-to-cylinder distribution. Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine, and because exhaust cleanup devices such as the catalytic converter can be optimized to operate more efficiently since the exhaust is of consistent and predictable composition.

Fuel injection generally increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution, less fuel is needed for the same power output. When cylinder-to-cylinder distribution is less than ideal, as is always the case to some degree with a carburetor or throttle body fuel injection, some cylinders receive excess fuel as a side effect of ensuring that all cylinders receive sufficient fuel. Power output is asymmetrical with respect to air/fuel ratio; burning extra fuel in the rich cylinders does not reduce power nearly as quickly as burning too little fuel in the lean cylinders. However, rich-running cylinders are undesirable from the standpoint of exhaust emissions, fuel efficiency, engine wear, and engine oil contamination. Deviations from perfect air/fuel distribution, however subtle, affect the emissions, by not letting the combustion events be at the chemically ideal (stoichiometric) air/fuel ratio. Grosser distribution problems eventually begin to reduce efficiency, and the grossest distribution issues finally affect power. Increasingly poorer air/fuel distribution affects emissions, efficiency, and power, in that order. By optimizing the homogeneity of cylinder-to-cylinder mixture distribution, all the cylinders approach their maximum power potential and the engine's overall power output improves.

A fuel-injected engine often produces more power than an equivalent carbureted engine. Fuel injection alone does not necessarily increase an engine's maximum potential output. Increased airflow is needed to burn more fuel, which in turn releases more energy and produces more power. The combustion process converts the fuel's chemical energy into heat energy, whether the fuel is supplied by fuel injectors or a carburetor. However, airflow is often improved with fuel injection, the components of which allow more design freedom to improve the air's path into the engine. In contrast, a carburetor's mounting options are limited because it is larger, it must be carefully oriented with respect to gravity, and it must be equidistant from each of the engine's cylinders to the maximum practicable degree. These design constraints generally compromise airflow into the engine. Furthermore, a carburetor relies on a restrictive venturi to create a local air pressure difference, which forces the fuel into the air stream. The flow loss caused by the venturi, however, is small compared to other flow losses in the induction system. In a well-designed carburetor induction system, the venturi is not a significant airflow restriction.

Fuel is saved while the car is coasting because the car's movement is helping to keep the engine rotating, so less fuel is used for this purpose. Control units on modern cars react to this and reduce or stop fuel flow to the engine reducing wear on the brakes.

History and development

Herbert Akroyd Stuart developed the first system laid out on modern lines (with a highly-accurate 'jerk pump' to meter out fuel oil at high pressure to an injector. This system was used on the hot bulb engine and was adapted and improved by Robert Bosch for use on diesel engines — Rudolf Diesel's original system employed a cumbersome 'air-blast' system using highly compressed air.

The first use of direct gasoline injection was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925. Hesselman engines use the ultra lean burn principle; fuel is injected toward the end of the compression stroke, then ignited with a spark plug. They are often started on gasoline and then switched to diesel or kerosene. Fuel injection was in widespread commercial use in diesel engines by the mid-1920s. Because of its greater immunity to wildly changing g-forces on the engine, the concept was adapted for use in gasoline-powered aircraft during World War II, and direct injection was employed in some notable designs like the Junkers Jumo 210, the Daimler-Benz DB 601, the BMW 801, the Shvetsov ASh-82FN (M-82FN) and later versions of the Wright R-3350 used in the B-29 Superfortress.

Alfa Romeo tested one of the very first electric injection systems (Caproni-Fuscaldo) in Alfa Romeo 6C2500 with "Ala spessa" body in 1940 Mille Miglia. The engine had six electrically operated injectors and were fed by a semi-high pressure circulating fuel pump system.

Mechanical

The term Mechanical when applied to fuel injection is used to indicate that metering functions of the fuel injection (how the correct amount of fuel for any given situation is determined and delivered) is not achieved electronically but rather through mechanical means alone.

In the 1940s, hot rodder Stuart Hilborn offered mechanical injection for racers, salt cars, and midgets.

One of the first commercial gasoline injection systems was a mechanical system developed by Bosch and introduced in 1952 on the Goliath GP700 and Gutbrod Superior 600. This was basically a high pressure diesel direct-injection pump with an intake throttle valve set up. (Diesels only change amount of fuel injected to vary output; there is no throttle.) This system used a normal gasoline fuel pump, to provide fuel to a mechanically driven injection pump, which had separate plungers per injector to deliver a very high injection pressure directly into the combustion chamber.

Another mechanical system, also by Bosch, but injecting the fuel into the port above the intake valve was later used by Porsche from 1969 until 1973 for the 911 production range and until 1975 on the Carrera 3.0 in Europe. Porsche continued using it on its racing cars into the late seventies and early eighties. Porsche racing variants such as the 911 RSR 2.7 & 3.0, 904/6, 906, 907, 908, 910, 917 (in its regular normally aspirated or 5.5 Liter/1500 HP Turbocharged form), and 935 all used Bosch or Kugelfischer built variants of injection. The Kugelfischer system was also used by the BMW 2000/2002 Tii and some versions of the Peugeot 404/504 and Lancia Flavia. Lucas also offered a mechanical system which was used by some Maserati, Aston Martin and Triumph models between ca. 1963 and 1973.

A system similar to the Bosch inline mechanical pump was built by SPICA for Alfa Romeo, used on the Alfa Romeo Montreal and on US market 1750 and 2000 models from 1969-1981. This was specifically designed to meet the US emission requirements, and allowed Alfa to meet these requirements with no loss in performance and a reduction in fuel consumption.

Chevrolet introduced a mechanical fuel injection option, made by General Motors' Rochester Products division, for its 283 V8 engine in 1956 (1957 US model year). This system directed the inducted engine air across a "spoon shaped" plunger that moved in proportion to the air volume. The plunger connected to the fuel metering system which mechanically dispensed fuel to the cylinders via distribution tubes. This system was not a "pulse" or intermittent injection, but rather a constant flow system, metering fuel to all cylinders simultaneously from a central "spider" of injection lines. The fuel meter adjusted the amount of flow according to engine speed and load, and included a fuel reservoir, which was similar to a carburetor's float chamber. With its own high-pressure fuel pump driven by a cable from the distributor to the fuel meter, the system supplied the necessary pressure for injection. This was "port" injection, however, in which the injectors are located in the intake manifold, very near the intake valve. (Direct fuel injection is a fairly recent innovation for automobile engines. As recent as 1954 in the aforementioned Mercedes-Benz 300SL or the Gutbrod in 1953.) The highest performance version of the fuel injected engine was rated at from . This made it among the early production engines in history to exceed 1 hp/in³ (45.5 kW/L), after Chrysler's Hemi engine and a number of others. General Motors' fuel injected engine — usually referred to as the "fuelie" — was optional on the Corvette for the 1957 model year.

During the 1960s, other mechanical injection systems such as Hilborn were occasionally used on modified American V8 engines in various racing applications such as drag racing, oval racing, and road racing. These racing-derived systems were not suitable for everyday street use, having no provisions for low speed metering or even starting (fuel had to be squirted into the injector tubes while cranking the engine in order to start it). However they were a favorite in the aforementioned competition trials in which essentially wide-open throttle operation was prevalent.

Electronic

The first commercial electronic fuel injection (EFI) system was Electrojector, developed by the Bendix Corporation and was to be offered by American Motors (AMC) in 1957. A special muscle car model, the Rambler Rebel, showcased AMC's new engine. The Electrojector was an option and rated at . With no Venturi effect or heated carburetor (to help vaporize the gasoline) AMC's EFI equipped engine breathed easier with denser cold air to pack more power sooner and it reached peak torque 500 rpm quicker. Initial press information about the Bendix system in December 1956 was followed in March 1957 by a price bulletin that pegged the option at US$395, but due to supplier difficulties, fuel-injected Rebels would only be available after June 15. This was to have been the first production EFI engine, but Electrojector's teething problems meant only pre-production cars were so equipped: thus, very few cars so equipped were ever sold and none were made available to the public. The EFI system in the Rambler was a far more-advanced setup than the mechanical types then appearing on the market and the engines ran fine in warm weather, but suffered hard starting in cooler temperatures

In 1982, Bosch introduced a sensor that directly measures the air mass flow into the engine, on their L-Jetronic system. Bosch called this LH-Jetronic (L for Luftmasse and H for Hitzdraht, German for "air mass" and "hot wire", respectively). The mass air sensor utilizes a heated platinum wire placed in the incoming air flow. The rate of the wire's cooling is proportional to the air mass flowing across the wire. Since the hot wire sensor directly measures air mass, the need for additional temperature and pressure sensors is eliminated. The LH-Jetronic system was also the first fully-digital EFI system, which is now the standard approach. The advent of the digital microprocessor permitted the integration of all powertrain sub-systems into a single control module.

Supersession of carburetors

When efficient combustion takes place in an internal combustion engine, the proper number of fuel molecules and oxygen molecules are sent to the engine's combustion chamber(s), where fuel combustion (i.e., fuel oxidation) takes place. When efficient combustion takes place, neither extra fuel or extra oxygen molecules remain: each fuel molecule is matched with the appropriate number of oxygen molecules. This balanced condition is called stoichiometry.

In the 1970s and 1980s in the US, the federal government imposed increasingly strict exhaust emission regulations. During that time period, the vast majority of gasoline-fueled automobile and light truck engines did not use fuel injection. To comply with the new regulations, automobile manufacturers often made extensive and complex modifications to the engine carburetor(s). While a simple carburetor system has certain advantages compared to the fuel injection systems that were available during the 1970s and 1980s (including lower manufacturing cost), the more complex carburetor systems installed on many engines beginning in the early 1970s did not usually have these advantages. So in order to more easily comply with government emissions control regulations, automobile manufacturers, beginning in the late 1970s, furnished more of their gasoline-fueled engines with fuel injection systems, and fewer with complex carburetor systems.

There are three primary types of toxic emissions from an internal combustion engine: Carbon Monoxide (CO), unburnt hydrocarbons (HC), and oxides of nitrogen (NOx). CO and HC result from incomplete combustion of fuel due to insufficient oxygen in the combustion chamber. NOx, in contrast, results from excessive oxygen in the combustion chamber. The opposite causes of these pollutants makes it difficult to control all three simultaneously. Once the permissible emission levels dropped below a certain point, catalytic treatment of these three main pollutants became necessary. This required a particularly large increase in fuel metering accuracy and precision, for simultaneous catalysis of all three pollutants requires that the fuel/air mixture be held within a very narrow range of stoichiometry. The open loop fuel injection systems had already improved cylinder-to-cylinder fuel distribution and engine operation over a wide temperature range, but did not offer sufficient fuel/air mixture control to enable effective exhaust catalysis. Closed loop fuel injection systems improved the air/fuel mixture control with an exhaust gas oxygen sensor. The O₂ sensor is mounted in the exhaust system upstream of the catalytic converter, and enables the engine management computer to determine and adjust the air/fuel ratio precisely and quickly.

Fuel injection was phased in through the latter '70s and '80s at an accelerating rate, with the US, French and German markets leading and the UK and Commonwealth markets lagging somewhat, and since the early 1990s, almost all gasoline passenger cars sold in first world markets like the United States, Canada, Europe, Japan, and Australia have come equipped with electronic fuel injection (EFI). Many motorcycles still utilize carbureted engines, though all current high-performance designs have switched to EFI.

Fuel injection systems have evolved significantly since the mid-1980s. Current systems provide an accurate, reliable and cost-effective method of metering fuel and providing maximum engine efficiency with clean exhaust emissions, which is why EFI systems have replaced carburetors in the marketplace. EFI is becoming more reliable and less expensive through widespread usage. At the same time, carburetors are becoming less available, and more expensive. Even marine applications are adopting EFI as reliability improves. Virtually all internal combustion engines, including motorcycles, off-road vehicles, and outdoor power equipment, may eventually use some form of fuel injection.

The carburetor remains in use in developing countries where vehicle emissions are unregulated and diagnostic and repair infrastructure is sparse. Fuel injection is gradually replacing carburetors in these nations too as they adopt emission regulations conceptually similar to those in force in Europe, Japan, Australia and North America.

Basic function

The process of determining the necessary amount of fuel, and its delivery into the engine, are known as fuel metering. Early injection systems used mechanical methods to meter fuel (non electronic, or mechanical fuel injection). Modern systems are nearly all electronic, and use an electronic solenoid (the injector) to inject the fuel. An electronic engine control unit calculates the mass of fuel to inject.

Modern fuel injection schemes follow much the same setup. There is a mass airflow sensor or manifold absolute pressure sensor at the intake, typically mounted either in the air tube feeding from the air filter box to the throttle body, or mounted directly to the throttle body itself. The mass airflow sensor does exactly what its name implies; it senses the mass of the air that flows past it, giving the computer an accurate idea of how much air is entering the engine. The next component in line is the Throttle Body. The throttle body has a throttle position sensor mounted onto it, typically on the butterfly valve of the throttle body. The throttle position sensor (TPS) reports to the computer the position of the throttle butterfly valve, which the ECM uses to calculate the load upon the engine. The fuel system consists of a fuel pump (typically mounted in-tank), a fuel pressure regulator, fuel lines (composed of either high strength plastic, metal, or reinforced rubber), a fuel rail that the injectors connect to, and the fuel injector(s). There is a coolant temperature sensor that reports the engine temperature to the ECM, which the engine uses to calculate the proper fuel ratio required. In sequential fuel injection systems there is a camshaft position sensor, which the ECM uses to determine which fuel injector to fire. The last component is the oxygen sensor. After the vehicle has warmed up, it uses the signal from the oxygen sensor to perform fine tuning of the fuel trim.

The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the engine's air stream. In almost all cases this requires an external pump. The pump and injector are only two of several components in a complete fuel injection system.

In contrast to an EFI system, a carburetor directs the induction air through a venturi, which generates a minute difference in air pressure. The minute air pressure differences both emulsify (premix fuel with air) the fuel, and then acts as the force to push the mixture from the carburetor nozzle into the induction air stream. As more air enters the engine, a greater pressure difference is generated, and more fuel is metered into the engine. A carburetor is a self-contained fuel metering system, and is cost competitive when compared to a complete EFI system.

An EFI system requires several peripheral components in addition to the injector(s), in order to duplicate all the functions of a carburetor. A point worth noting during times of fuel metering repair is that early EFI systems are prone to diagnostic ambiguity. A single carburetor replacement can accomplish what might require numerous repair attempts to identify which one of the several EFI system components is malfunctioning. Newer EFI systems since the advent of OBD II diagnostic systems, can be very easy to diagnose due to the increased ability to monitor the realtime data streams from the individual sensors. This gives the diagnosing technician realtime feedback as to the cause of the drivability concern, and can dramatically shorten the number of diagnostic steps required to ascertain the cause of failure, something which isn't as simple to do with a carburetor. On the other hand, EFI systems require little regular maintenance; a carburetor typically requires seasonal and/or altitude adjustments.

Detailed function

Note: These examples specifically apply to a modern EFI gasoline engine. Parallels to fuels other than gasoline can be made, but only conceptually.

Typical EFI components

Injectors

Fuel Pump

Fuel Pressure Regulator

ECM - Engine Control Module; includes a digital computer and circuitry to communicate with sensors and control outputs.

Wiring Harness

Various Sensors (Some of the sensors required are listed here.)

:*Crank/Cam Position: Hall effect sensor :*Airflow: MAF sensor, sometimes this is inferred with a MAP sensor :*Exhaust Gas Oxygen: Oxygen sensor, EGO sensor, UEGO sensor

Functional description

Central to an EFI system is a computer called the Engine Control Unit (ECU), which monitors engine operating parameters via various sensors. The ECU interprets these parameters in order to calculate the appropriate amount of fuel to be injected, among other tasks, and controls engine operation by manipulating fuel and/or air flow as well as other variables. The optimum amount of injected fuel depends on conditions such as engine and ambient temperatures, engine speed and workload, and exhaust gas composition.

The electronic fuel injector is normally closed, and opens to inject pressurized fuel as long as electricity is applied to the injector's solenoid coil. The duration of this operation, called the pulse width, is proportional to the amount of fuel desired. The electric pulse may be applied in closely-controlled sequence with the valve events on each individual cylinder (in a sequential fuel injection system), or in groups of less than the total number of injectors (in a batch fire system).

Since the nature of fuel injection dispenses fuel in discrete amounts, and since the nature of the 4-stroke engine has discrete induction (air-intake) events, the ECU calculates fuel in discrete amounts. In a sequential system, the injected fuel mass is tailored for each individual induction event. Every induction event, of every cylinder, of the entire engine, is a separate fuel mass calculation, and each injector receives a unique pulse width based on that cylinder's fuel requirements.

It is necessary to know the mass of air the engine "breathes" during each induction event. This is proportional to the intake manifold's air pressure/temperature, which is proportional to throttle position. The amount of air inducted in each intake event is known as "air-charge", and this can be determined using several methods. (See MAF sensor, and MAP sensor.)

The three elemental ingredients for combustion are fuel, air and ignition. However, complete combustion can only occur if the air and fuel is present in the exact stoichiometric ratio, which allows all the carbon and hydrogen from the fuel to combine with all the oxygen in the air, with no undesirable polluting leftovers. Oxygen sensors monitor the amount of oxygen in the exhaust, and the ECU uses this information to adjust the air-to-fuel ratio in real-time.

To achieve stoichiometry, the air mass flow into the engine is measured and multiplied by the stoichiometric air/fuel ratio 14.64:1 (by weight) for gasoline. The required fuel mass that must be injected into the engine is then translated to the required pulse width for the fuel injector. The stoichiometric ratio changes as a function of the fuel; diesel, gasoline, ethanol, methanol, propane, methane (natural gas), or hydrogen.

Deviations from stoichiometry are required during non-standard operating conditions such as heavy load, or cold operation, in which case, the mixture ratio can range from 10:1 to 18:1 (for gasoline). In early fuel injection systems this was accomplished with a thermotime switch.

Pulse width is inversely related to pressure difference across the injector inlet and outlet. For example, if the fuel line pressure increases (injector inlet), or the manifold pressure decreases (injector outlet), a smaller pulse width will admit the same fuel. Fuel injectors are available in various sizes and spray characteristics as well. Compensation for these and many other factors are programmed into the ECU's software.

Sample pulsewidth calculations

Note: These calculations are based on a 4-stroke-cycle, 5.0L, V-8, gasoline engine. The variables used are real data.

Calculate injector pulsewidth from airflow

:First the CPU determines the air mass flow rate from the sensors - $Mass\_\{air\}/Minute$. (The various methods to determine airflow are beyond the scope of this topic. See MAF sensor, or MAP sensor.)

::$\backslash frac\{Mass\_\{air\}\}\{Minute\}\; \backslash times\; \backslash frac\{Minutes\}\{Revolution\}\; \backslash times\; \backslash frac\{Revolutions\}\{Stroke\}\; =\backslash frac\{Mass\_\{air\}\}\{Stroke\}$

::::$Minutes/Revolution$ is the reciprocal of engine speed (RPM).

::::The term $Revolutions/Stroke=1/2$, whether it's a four stroke or a two-stroke engine.

::$\backslash frac\{Mass\_\{air\}\}\{Stroke\_\{intake\}\}\; \backslash times\; \backslash frac\{Mass\_\{Fuel\}\}\{Mass\_\{Air\}\}=\backslash frac\{Mass\_\{Fuel\}\}\{Stroke\_\{intake\}\}$

::::$Mass\_\{Fuel\}/Mass\_\{Air\}$ is the desired mixture ratio, usually stoichiometric, but often different depending on operating conditions.''

::$\backslash frac\{Mass\_\{Fuel\}\}\{Stroke\_\{intake\}\}\; \backslash times\; \backslash frac\{1\}\{Mass\_\{Fuel\}/Minute\}\; =\backslash frac\{Minutes\}\{Stroke\_\{intake\}\}=Pulsewidth$

::::$1/(Mass\_\{Fuel\}/Minute)$ is the flow capacity of the injector, or its size.

:Combining the above three terms . . .

$\backslash frac\{Mass\_\{air\}\}\{Minute\}\; \backslash times\; \backslash frac\{Minutes\}\{Revolution\}\; \backslash times\; \backslash frac\{Revolutions\}\{Stroke\}\; \backslash times\; \backslash frac\{Mass\_\{Fuel\}\}\{Mass\_\{Air\}\}\; \backslash times\; \backslash frac\{1\}\{Mass\_\{Fuel\}/Minute\}\; =\; Pulsewidth$

:Substituting real variables for the 5.0 L engine at idle.

:: * $0.55\; \backslash frac\{lb\}\{min\}\; \backslash times\; \backslash frac\{1\; min\}\{700\; rev\}\; \backslash times\; \backslash frac\{1\; revolution\}\{2\; strokes\}\; \backslash times\; \backslash frac\{1\}\{14.64\}\; \backslash times\; 2.5\backslash frac\{min\}\{lb\}\; =\; 6.7\; \backslash times\; 10^\{-5\}\; min\; =\; 4ms$

:Substituting real variables for the 5.0 L engine at maximum power.

:: * $28\; \backslash frac\{lb\}\{min\}\; \backslash times\; \backslash frac\{1\; min\}\{5500\; rev\}\; \backslash times\; \backslash frac\{1\; revolution\}\{2\; strokes\}\; \backslash times\; \backslash frac\{1\}\{11.00\}\; \backslash times\; 2.5\backslash frac\{min\}\{lb\}\; =\; 57.9\; \backslash times\; 10^\{-5\}\; min\; =\; 35ms$

:

Injector pulsewidth typically ranges from 4 ms/engine-cycle at idle, to 35 ms per engine-cycle at wide-open throttle. The pulsewidth accuracy is approximately 0.01 ms.

Calculate fuel-flow rate from pulsewidth

::*(Fuel flow rate) ≈ (pulsewidth) × (engine speed) × (number of fuel injectors)

::::Looking at it another way:

::*(Fuel flow rate) ≈ (throttle position) × (rpm) × (cylinders)

::::Looking at it another way:

::*(Fuel flow rate) ≈ (air-charge) × (fuel/air) × (rpm) × (cylinders)

:Substituting real variables for the 5.0 L engine at idle.

::*(Fuel flow rate) = (2.0 ms/intake-stroke) × (hour/3,600,000 ms) × (24 lb-fuel/hour) × (4-intake-stroke/rev) × (700 rev/min) × (60 min/h) = (2.24 lb/h)

:Substituting real variables for the 5.0L engine at maximum power.

::*(Fuel flow rate) = (17.3 ms/intake-stroke) × (hour/3,600,000-ms) × (24 lb-fuel/hour) × (4-intake-stroke/rev) × (5500-rev/min) × (60-min/hour) = (152 lb/h)

:

The fuel consumption rate is 68 times greater at maximum engine output than at idle. This dynamic range of fuel flow is typical of a naturally aspirated passenger car engine. The dynamic range is greater on a supercharged or turbocharged engine. It is interesting to note that 15 gallons of gasoline will be consumed in 37 minutes if maximum output is sustained. On the other hand, this engine could continuously idle for almost 42 hours on the same 15 gallons.

Various injection schemes

===Throttle body injection=== Throttle-body injection (called TBI by General Motors and Central Fuel Injection (CFI) by Ford) or single-point injection was introduced in the 1940s in large aircraft engines (then called the pressure carburetor) and in the 1980s in the automotive world. The TBI system injects fuel at the throttle body (the same location where a carburetor introduced fuel). The induction mixture passes through the intake runners like a carburetor system, and is thus labelled a "wet manifold system". Fuel pressure is usually specified to be in the area of 10-15 psi. The justification for the TBI/CFI phase was low cost. Many of the carburetor's supporting components could be reused such as the air cleaner, intake manifold, and fuel line routing. This postponed the redesign and tooling costs of these components. Most of these components were later redesigned for the next phase of fuel injection's evolution, which is individual port injection, commonly known as MPFI or "multi-point fuel injection". TBI was used extensively on American-made passenger cars and light trucks in the 1980-1995 timeframe and some transition-engined European cars throughout the early and mid-1990s.

Continuous injection

In a continuous injection system, fuel flows at all times from the fuel injectors, but at a variable rate. This is in contrast to most fuel injection systems, which provide fuel during short pulses of varying duration, with a constant rate of flow during each pulse. Continuous injection systems can be multi-point or single-point, but not direct.

The most common automotive continuous injection system is Bosch's K-Jetronic (K for kontinuierlich, German for "continuous" — a.k.a. CIS — Continuous Injection System), introduced in 1974. Gasoline is pumped from the fuel tank to a large control valve called a fuel distributor, which separates the single fuel supply pipe from the tank into smaller pipes, 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 the air vane, which in turn is determined by the volume flowrate of air past 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. On cars equipped with an oxygen sensor, the fuel mixture is adjusted by a device called the frequency valve. 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 was used for many years between 1974 and the mid 1990s by BMW, Lamborghini, Ferrari, Mercedes-Benz, Volkswagen, Ford, Porsche, Audi, Saab, DeLorean, and Volvo. There was also a variant of the system called KE-Jetronic with electronic instead of mechanical control of the control pressure. Some Toyotas and other Japanese cars from the 1970s to the early 1990s used an application of Bosch's multipoint L-Jetronic system manufactured under license by DENSO. Chrysler used a similar continuous fuel injection system on the 1981-1983 Imperial.

In piston aircraft engines, continuous-flow fuel injection is the most common type. In contrast to automotive fuel injection systems, aircraft continuous flow fuel injection is all mechanical, requiring no electricity to operate. Two common types exist: the Bendix RSA system, and the TCM system. The Bendix system is a direct descendant of the pressure carburetor. However, instead of having a discharge valve in the barrel, it uses a flow divider mounted on top of the engine, which controls the discharge rate and evenly distributes the fuel to stainless steel injection lines which go to the intake ports of each cylinder. The TCM system is even more simple. It has no venturi, no pressure chambers, no diaphragms, and no discharge valve. The control unit is fed by a constant-pressure fuel pump. The control unit simply uses a butterfly valve for the air which is linked by a mechanical linkage to a rotary valve for the fuel. Inside the control unit is another restriction which is used to control the fuel mixture. The pressure drop across the restrictions in the control unit controls the amount of fuel flowing, so that fuel flow is directly proportional to the pressure at the flow divider. In fact, most aircraft using the TCM fuel injection system feature a fuel flow gauge which is actually a pressure gauge that has been calibrated in gallons per hour or pounds per hour of fuel.

Central port injection (CPI)

General Motors implemented a system called "central port injection" (CPI) or "central port fuel injection" (CPFI). It uses tubes with poppet valves from a central injector to spray fuel at each intake port rather than the central throttle-body. Pressure specifications typically mirror that of a TBI system. The two variants were CPFI from 1992 to 1995, and CSFI from 1996 and on. CPFI is a batch-fire system, in which fuel is injected to all ports simultaneously. The 1996 and later CSFI system sprays fuel sequentially.

===Multi-point fuel injection=== Multi-point fuel injection injects fuel into the intake port just upstream of the cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; or simultaneous, in which fuel is injected at the same time to all the cylinders. The intake is only slightly wet, and typical fuel pressure runs between 40-60 psi.

Many modern EFI systems utilize sequential MPFI; however, in newer gasoline engines, direct injection systems are beginning to replace sequential ones.

Direct injection

Direct fuel injection costs more than indirect injection systems: the injectors are exposed to more heat and pressure, so more costly materials and higher-precision electronic management systems are required. However, the entire intake is dry, making this a very clean system. In a common rail system, the fuel from the fuel tank is supplied to the common header (called the accumulator). This fuel is then sent through tubing to the injectors which inject it into the combustion chamber. The header has a high pressure relief valve to maintain the pressure in the header and return the excess fuel to the fuel tank. The fuel is sprayed with the help of a nozzle which is opened and closed with a needle valve, operated with a solenoid. When the solenoid is not activated, the spring forces the needle valve into the nozzle passage and prevents the injection of fuel into the cylinder. The solenoid lifts the needle valve from the valve seat, and fuel under pressure is sent in the engine cylinder. Third-generation common rail diesels use piezoelectric injectors for increased precision, with fuel pressures up to .

Gasoline engines incorporate gasoline direct injection engine technology.

Diesel engines

Diesel engines must use fuel injection, and it must be timed (unlike on petrol engines). Throughout the early history of diesels, they were always fed by a mechanical pump with a small separate cylinder for each cylinder, feeding separate fuel lines and individual injectors. Most such pumps were in-line, though some were rotary.

Earlier systems, relying on crude injectors, often injected into a sub-chamber shaped to swirl the compressed air and improve combustion; this was known as indirect injection. However, it was less thermally efficient than the now universal direct injection in which initiation of combustion takes place in a depression (often toroidal) in the crown of the piston.

Petrol/gasoline engines

Modern petrol engines (gasoline engines) also utilise direct injection, which is referred to as gasoline direct injection. This is the next step in evolution from multi-point fuel injection, and offers another magnitude of emission control by eliminating the "wet" portion of the induction system along the inlet tract.

By virtue of better dispersion and homogeneity of the directly injected fuel, the cylinder and piston are cooled, thereby permitting higher compression ratios and more aggressive ignition timing, with resultant enhanced power output. More precise management of the fuel injection event also enables better control of emissions. Finally, the homogeneity of the fuel mixture allows for leaner air/fuel ratios, which together with more precise ignition timing can improve fuel efficiency. Along with this, the engine can operate with stratified (lean burn) mixtures, and hence avoid throttling losses at low and part engine load. Some direct-injection systems incorporate piezoelectronic fuel injectors. With their extremely fast response time, multiple injection events can occur during each cycle of each cylinder of the engine.

The first use of direct petrol injection was on the Hesselman engine, invented by Swedish engineer Jonas Hesselman in 1925.

Maintenance hazards

Fuel injection introduces potential hazards in engine maintenance due to the high fuel pressures used. Residual pressure can remain in the fuel lines long after an injection-equipped engine has been shut down. This residual pressure must be relieved, and if it is done so by external bleed-off, the fuel must be safely contained. If a high-pressure diesel fuel injector is removed from its seat and operated in open air, there is a risk to the operator of injury by hypodermic jet-injection, even with only pressure. The first known such injury occurred in 1937 during a diesel engine maintenance operation.

See also

Natural gas

Notes

External links

History of the D Jetronic system

High Quality Fuel System Repairs Guide

How Fuel Injection Systems Work

Category:Engine fuel system technology Category:Fuel injection systems Category:Engine components

Name	Isabel Pantoja
Imgsize	200px
Background	solo_singer
Birth name	María Isabel Pantoja Martín
Alias	La Pantoja
Born	August 04, 1956 Seville, Spain
Occupation	Singer
Url	http://www.isabelpantoja.es

Isabel Pantoja (born August 4, 1956) is a popular contemporary Spanish singer. She is of Romani (Gypsy) origin, born in the Triana district of Seville, Spain. She has released more than a dozen albums throughout a career spanning many decades, and is known for her distinctive Andalusian style.

Biography

She was born into a musicians family, both, her father and her grandfather, being singers.

Her husband, the bullfighter Francisco Rivera Pérez "Paquirri", died in the bullring on 26 September 1984, at the horns of the now infamous bull Avispado in Pozoblanco, Córdoba. She has a son with Paquirri named Francisco Rivera Pantoja-

Discography

1974 - Fue por tu voz

1975 - Que dile y dile

1976 - Niña Isabela

1978 - Y no estaba muerto, no, no

1979 - 22 Abriles tengo

1981 - A la limón!

1981 - Amante, amante

1982 - ¡Viva Triana!

1983 - Cambiar por ti

1985 - Marinero de luces

1987 - Tú serás mi Navidad

1988 - Desde Andalucía

1989 - Se me enamora el alma

1990 - La canción española

1992 - Corazón herido

1993 - De nadie

1996 - Amor eterno

1998 - Veneno

1999 - A tu vera

2002 - Donde el corazón me lleve

2003 - Soy como soy: Grandes éxitos

2003 - Mi Navidad flamenca

2004 - Buena suerte

2005 - By Pumpin' Dolls

2005 - Sinfonía de la Copla

2005 - Mi canción de Navidad

2006 - 10 boleros y una canción de amor

References

External links

Official site in Spanish and English

Category:1956 births Category:1970s singers Category:1980s singers Category:1990s singers Category:2000s singers Category:2010s singers Category:Living people Category:People from Seville Category:Spanish Romani people Category:Spanish singers Category:Spanish female singers Category:Spanish-language singers Category:Spanish Roman Catholics

Name	'Umar
Title	Al-Farooq
Caption	Caliph Umar's empire at its peak, 644.
Reign	23 August 634–7 November 644
Predecessor	Abu Bakr
Successor	Uthman
Date of birth	586–590
Place of birth	Mecca, Arabia
Date of death	7 November 644
Place of death	Medina, Arabia
Buried	Al-Masjid al-Nabawi, Madinah
Other titles	Al-Farooq

Umar (, c. 586–590 644) c. 2 Nov. (Dhu al-Hijjah 26, 23 Hijri), also known as Omar, was a friend of the Islamic prophet, Muhammad, and one of his companions. He became the second Muslim ruler after Muhammad's death and ruled for 10 years.

Converting to Islam in the 6th year after Muhammad's first revelation, he spent 18 years in companionship of Muhammad. He succeeded Caliph Abu Bakr on 23 August 634 as the second Caliph, and played a significant role in Islam. Under Umar the Islamic empire expanded at an unprecedented rate ruling the whole Sassanid Persian Empire and more than two thirds of the Eastern Roman Empire. His legislative abilities, his firm political and administrative control over a rapidly expanding empire and his brilliantly coordinated multi-prong attacks against the Sassanid Persian Empire that resulted in the conquest of the Persian empire in less than two years, marked his reputation as a great political and military leader. He was killed by a Persian captive.

Sunni Muslims view him as the Second Rashidun and know him as Farooq the great. On the other hand, Shia Muslims view him doing Coup d'état against Ali's right to successorship and directly being responsible for Fatima's death.

Early life

Umar was born in Mecca to the Banu Adi clan, which was responsible for arbitrations among the tribes. His father was Khattab ibn Nufayl and his mother was Hantammah daughter of Khattab, from the tribe of Banu Makhzum. He is said to have belonged to a middle class family. In his youth he used to tend to his father’s camels in the plains near Mecca. His father was famed for his intelligence among his tribe. He was a middle class merchant and is believed to be a ruthless man and emotional polytheist who often treated Umar badly. As obvious from Umar's own statement regarding his father during his later political rule, Umar said, "My father Al-Khittab was a ruthless man. He used to make me work hard; if I didn't work he used to beat me and he used to work me to exhaustion."

Despite literacy being uncommon in pre-Islamic Arabia, Umar learned to read and write in his youth. Though not a poet himself, he developed a love for poetry and literature. According to the tradition of Quraish, while still in his teenage years, Umar learned martial arts, horse riding and wrestling. He was tall and physically powerful and was soon to became a renowned wrestler. Umar was also a gifted orator, and due to his intelligence and overwhelming personality, he succeeded his father as an arbitrator of conflicts among the tribes.

In addition, Umar followed the traditional profession of Quraish. He became a merchant and had several journeys to Rome and Persia, where he is said to have met the various scholars and analyzed the Roman and Persian societies closely. However, as a merchant he is believed to have never been successful. Drinking alcohol was very common among the Quraish, and Umar was also fond of drinking in his pre-Islamic days.

During Muhammad's era

Umar's hostility to Islam

In 610 Muhammad started delivering the message of Islam. Umar, alongside others in makkah, opposed Islam and threatened to kill Muhammad. He resolved to defend the traditional, polytheistic religion of Arabia. He was most adamant and cruel in opposing Muhammad and very prominent in persecuting the Muslims. Umar was the first man who resolved that Muhammad had to be murdered in order to finish Islam. Umar firmly believed in the unity of the Quraish and saw the new faith of Islam as a cause of division and discord among the Quraish.

Converting to Islam

Umar converted to Islam in 616, one year after the Migration to Abyssinia. The story was recounted in Ibn Ishaq's Sīrah; On the way to murder Muhammad, Umar met his best friend Nu'aim ibn Abdi 'Allah who had secretly been converted to a Muslim but he did not tell Umar anything about it. When Umar told him that he was going to kill Muhammad he was afraid. He knew Umar will attempt what he said. So just to divert his attention he told him to set his own house in order first, as his sister and her husband had converted to Islam. Upon arriving at her house, Umar found his sister and brother-in-law Saeed bin Zaid (Umar's cousin), reciting the verses of the Qur'an(Surah Taha). He started quarreling with his brother-in-law . When his sister came to rescue her husband, he also started quarreling with her. Yet still they kept on saying "you may kill us but we will not give up Islam". Upon hearing these words, Umar slapped his sister so hard that she fell to the ground bleeding from her mouth. When he saw what he did to his sister now, out of guilt he calmed down and asked his sister to give him what she was reciting. She gave him the paper on which was written the verses of the chapter Ta-Ha. He was so struck by the beauty of the verses that he accepted Islam that day. He then went to Muhammad with the same sword he intended to kill him with and accepted Islam in front of him and his companions. Umar was 27 when he accepted Islam. Following his conversion, Umar went to inform the chief of Quraish, Amr ibn Hishām, about his acceptance of Islam. According to one account, Umar thereafter openly prayed at the Kaaba as the Quraish chiefs, Amr ibn Hishām and Abu Sufyan ibn Harb, reportedly watched in anger. This further helped the Muslims to gain confidence in practicing Islam openly. At this stage Umar even challenged anyone who dared to stop the Muslims from praying, although no one dared to interfere with Umar when he was openly praying.

Umar’s conversion to Islam gave power to the Muslims and the faith in Mecca. It was after this that Muslims offered prayers openly in Masjid al-Haram for the first time. Abdullah bin Masoud said:

All these things earned Umar the title of Farooq, meaning one who makes a difference.

Umar's Title of Al Farooq

Mujahid, on the authority of Ibn Abbas related that he had asked 'Umar bin Al-Khattab why he had been given the epithet of Al-Farooq (he who distinguishes truth from falsehood), he replied: After I had embraced Islam, I asked the Prophet : 'Aren't we on the right path here and Hereafter?' The Prophet answered: 'Of course you are! I swear by Allâh in Whose Hand my soul is, that you are right in this world and in the hereafter.' I, therefore, asked the Prophet 'Why we then had to conduct clandestine activism. I swear by Allâh Who has sent you with the Truth, that we will leave our concealment and proclaim our noble cause publicly.' We then went out in two groups, Hamzah leading one and I the other. We headed for the Mosque in broad daylight when the polytheists of Quraish saw us, their faces went pale and got incredibly depressed and resentful. On that very occasion, the Prophet attached to me the epithet of Al-Farooq."

Migration to Medina

In 622 due to the growing popularity of Islam in the city of Yathrib (later renamed Medīnat an-Nabī, or simply Medina) Muhammad ordered his followers to migrate to Medina. Muslims usually migrated at night due to fear of Quraish's resistance to that migration, but Umar is reported to have migrated openly during the day time saying: Any one who wants to make his wife a widow and his children orphan. should come and meet me there behind that cliff." Umar migrated to Medina accompanied by his cousin and brother-in-law Saeed ibn Zaid. Later in the year Umar was a part of campaign against the Jewish tribe of Banu Nadir. In 625 Umar’s daughter Hafsah was married to Muhammad. Later in 627 he participated in the Battle of the Trench and also in the Battle of Banu Qurayza. In 628 Umar participated in the Treaty of Hudaybiyyah and was made one of the witness over the pact. In 630 when Muslim armies rushed for the Conquest of Mecca he was part of that army. Later in 630 he was part of Battle of Hunayn and Siege of Ta'if. He was part of Muslim's army that went for the campaign of Tabuk under Muhammad's command and he was reported to have given half of his wealth for the preparation of this expedition. He also participated in a farewell Hajj of Muhammad in 631.

Death of Muhammad

Muhammad died on 8 June 632. Umar was full of grief upon hearing the news, Umar, the devoted disciple, could not accept the reality that the "Messenger of God" has died. According to the Qur'an, "Muhammad is but a messenger; messengers have passed away before", i.e. died or killed. It is said that Umar promised to strike the head of any man who would say that Muhammad died. At this point Abu Bakr is reported to have come out to the Muslim community and gave his famous speech which included:

Abū Bakr then recited these verses from the Qur'an:

Hearing this from Abu Bakr, the most senior disciple of Muhammad, Umar then fell down on his knees in great sense of sorrow and acceptance of the reality. Sunni Muslims say that this denial of Muhammad's death was occasioned by his deep love for him. Prior to Battle of Yamamah, Umar pressured Abu Bakr to call back Khalid, who had killed Malik ibn Nuwayrah, a rebel chief who was a state criminal. Umar was reportedly misguided by Malik's brother that Malik was a Muslim and Khalid killed him because he wanted to marry his wife Layla bint al-Minhal, a renowned beauty in Arabia. While Abu Bakr refused to accept Umar's opinion and Umar continue insisting for Khalid disposal even after Khalid's conquest of Iraq. This became a major issue between Abu Bakr and Umar and a spacious chapter in Islamic history. It was Umar who advised Abu Bakr to compile Quran in the form of a book, after the death of 300 memorizers of Quran in Battle of Yamamah. Abu Bakr appointed Umar as his successor prior to his death in 634. He was confirmed in the office thereafter.

Appointment as a Caliph

Due to his strict and autocratic nature, Umar was not a very popular figure among the notables of Madinah and members of Majlis al Shura, accordingly succession of Umar was initially discouraged by high ranking companions of Abu Bakr. Nevertheless, Abu Bakr decided to make Umar, his successor. Umar, still was well known for his extraordinary will power, intelligence, political astuteness, impartiality, justice and care for poor and underprivileged people. Abu Bakr is reported to have said to the high-ranking advisers:

Abu Bakr was fully aware of Umar's power and ability to succeed him. Succession of Umar was thus not as troublesome as any of the others. His was perhaps one of the smoothest transitions to power from one authority to another in the Muslim lands. Abu Bakr before his death called Uthman to write his will in which he declared Umar his successor. In his will he instructed Umar to continue the conquests on Iraq and Syrian fronts. Abu Bakr's decision would prove to be crucial in the strengthening of the nascent Islamic empire.

Reign as Caliph

On 22 August Caliph Abu Bakr died. The same day Umar assumed the office of Caliphate. After the assumption of office as the Caliph, Umar addressed the Muslims in his Inaugural address as:

Initial challenges

Umar was already not an endearing figure in Medina. Although almost all of the Muslims had given pledge of loyalty to him, nevertheless he was rather more feared than loved. The first challenge for Umar was to win out his subjects and members of Majlis al Shura. Umar was a gifted orator, and he would use his ability to get a soft corner in the hearts of people. On Friday prayers Umar addressed the people as follow:

Umar's addresses greatly moved the people. Next time he addressed the people as:

There could be no better definition of the democracy and justice, then the historic words of Umar, over which he laid foundation of his rule:

Umar's stress was on the well being of poor and underprivileged people, as this class made a bulk of any community, the people were soundly moved by Umar's speeches and his popularity grew rapidly and continuously over the period of his reign. In addition to this Umar, in order to improve his reputation and relation with Banu Hashim, the tribe of Ali, delivered to him his disputed estates in Khayber. Though he followed Abu Bakr's decision over the dispute of land of Fidak, continued its status as a state property. In Ridda wars, thousands of prisoners from rebel and apostate tribes were taken away as slaves during the expeditions. Umar ordered the general amnesty for the prisoners, and their immediate emancipation. This made Umar quite a popular among the budoiene tribes. With necessary public support with him, Umar took a bold decision of retrieving Khalid ibn Walid from supreme command on Roman front.

Political and civil administration

The government of Umar was more or less a unitary government, where the sovereign political authority was the Caliph. The empire of Umar was divided into provinces and some autonomous territories like in some regions Azerbaijan and Armenia, that had accepted the suzerainty of the Caliphate. The provinces were administered by the provincial governors or Wali. The selection of which was made personally by Umar, who was very fastidious in it. Provinces were further divided into districts, there were about 100 districts in the empire. Each district or main city was under the charge of a junior governor or Wali, usually appointed by Umar himself, but occasionally they were also appointed by the provincial governor. Other officers at the provincial level were:

#Katib, the Chief Secretary. #Katib-ud-Diwan, the Military Secretary. #Sahib-ul-Kharaj, the Revenue Collector. #Sahib-ul-Ahdath, the Police chief. #Sahib-Bait-ul-Mal, the Treasury Officer. #Qadi, the Chief Judge.

In some districts there were separate military officers, though the Governor (Wali) was in most cases the Commander-in-chief of the army quartered in the province. Every appointment was made in writing. At the time of appointment an instrument of instructions was issued with a view to regulating the conduct of Governors. On assuming office, the Governor was required to assemble the people in the main mosque, and read the instrument of instructions before them.

Umar's general instructions to his officers were:

Various other strict code of conducts were to be obeyed by the governors and state officials. The principal officers were required to come to Mecca on the occasion of the Hajj, during which people were free to present any complaint against them. In order to minimize the chances of corruption, Umar made it a point to pay high salaries to the staff. Provincial governor received as much as five to seven thousand dirham annually besides their shares of the spoils of war (if they were also the commander in chief of the army of their sector). Under Umar the empire was divided into the following provinces.

#Arabia was divided into two provinces, Mecca and Medina; #Iraq was divided into two provinces, Basra and Kufa; #In the upper reaches of the Tigris and the Euphrates, Jazira was a province; #Syria was a province; #Umar divided Palestine in two provinces Aylya and Ramlah; #Egypt was divided into two provinces, Upper Egypt and Lower Egypt; #Persia was divided into three provinces, Khorasan; Azarbaijan and Fars.

Umar was first to established a special department for the investigation of complaints against the officers of the State. This department acted as Administrative court, where the legal proceedings were personally led by Umar. The Department was under the charge of Muhammad ibn Maslamah, one of Umar's most trusted man. In important cases Muhammad ibn Maslamah was deputed by Umar to proceed to the spot, investigate the charge and take action. Sometimes an Inquiry Commission was constituted to investigate the charge. On occasions the officers against whom complaints were received were summoned to Medina, and charged in Umar's administrative court. One of Umar's most powerful department was his intelligence department of secret services. Umar's iron fist rule on his empire, is often credited to this institution . His agents were everywhere, in the army, in the bureaucracy and in the enemy land. For the officials of Umar it was said to be the most fearsome department.

Umar was a pioneer in some affairs:

# Umar was the first to introduce the public ministry system, where the records of officials and soldiers were kept. He also kept a record system that had the messages he sent to Governors and heads of states. # He was the first to appoint police forces to keep civil order. # He was the first to discipline the people when they became disordered.

Reforms

Umar is regarded as one of the greatest political geniuses in history. Umar also ordered the expulsion of the Christian and Jewish communities of Najran and Khaybar allowing them to reside in Syria or Iraq. He issued orders that these Christians and Jews should be treated well and allotted them the equivalent land in their new settlements. Umar also forbade non-Muslims to reside in the Hejaz for longer than three days. He was first to establish army as a state department. Umar was founder of Fiqh, the Islamic jurisprudence. He is regarded by Sunni Muslims to be one of the greatest Faqih. Umar as a jurist started the process of codifying Islamic Law. In 641, he established Bayt al-mal, a financial institution and started annual allowance for the Muslims. A year later he also started allowance for the poor, underprivileged and old non-Muslim citizens of the empire. As a leader, 'Umar was known for his simple, austere lifestyle. Rather than adopt the pomp and display affected by the rulers of the time, he continued to live much as he had when Muslims were poor and persecuted. In 639, his fourth year as caliph and the seventeenth year 17 since the Hijra, he decreed that the Islamic calendar should be counted from the year of the Hijra of Muhammad from Mecca to Madinah.

Military expansion

It is widely believed that Umar stressed more on consolidating his power and political influence in the conquered land, rather than pursuing conquests. Nevertheless under Umar, The Islamic empire grew at an unprecedented rate. In 638, after the conquest of Syria, Umar dismissed Khalid, his most successful general due to his every growing fame and influence. Later however Umar regretted over his decision. The military conquest were partially terminated between 638–639 during the years of great famine and plague in Arabia and Levant respectively. During his reign Levant, Egypt, Cyrenaica, Tripolitania, Fezzan, Eastern Anatolia, almost whole of Sassanid Persian Empire including Bactria, Persia, Azerbaijan, Armenia, Caucasus and Makran were annexed to Islamic Empire. Accordiong to one estimate more than 4050 cities were captured during these military conquest. Prior to his death in 644, Umar had ceased all military expeditions apparently to consolidate his rule in Egypt and newly conquered Sassanid Empire (642–644). At his death in November 644, domain of his rule extended from present day Libya in west to Indus river in east and Oxus river in north.

The great famine

In the year 638, Arabia fell into severe drought followed by a famine. Bedouin people began to die because of hunger and epidemic disease. Hundreds of thousands of people from all over Arabia gathered at Madinah where food was rationed. Soon the reserves of food at Madinah began to decline, and Umar wrote to the provincial governors of Syria, Palestine and Iraq for aid. A state of emergency was declared in Madinah and Arabia. The timely aid of Umar's governors saved the lives of thousands of people through out Arabia. The first governor to respond was Abu Ubaidah ibn al-Jarrah, the governor of Syria and supreme commander of Rashidun army. He sent a historic letter to Umar saying

Later, Abu Ubaidah paid a personal visit to Madinah and acted as an officer of Disaster management cell, which was headed personally by Umar. Once an adequate supply of rations reached Madinah, Umar dispatched his men to the routes of Iraq, Palestine and Syria to take the supply caravans to the desert settlements deeper into Arabia, which in turn saved millions from starvation. For internally displaced people, Umar hosted a dinner every night at Madinah, which according to one estimate had attendance of more than hundred thousand people. By early 639 conditions begun to improve. Arabia received precipitation and as soon as the famine ended, Umar personally supervised the rehabilitation of the displaced people. They were given adequate amounts of rations and were exempted from payment of zakat for that year and the next year.

The great plague

While famine was ending in Arabia, many districts in Syria and Palestine were devastated by plague. While Umar was on his way to visit Syria, at Elat, he was received by Abu Ubaidah ibn al-Jarrah, governor of Syria, who informed him about plague and its intensity and he was suggest to go back to Madinah. Umar tried to persuade Abu Ubaidah to come with him to Madinah but he denied to leave his troops in that critical situation. Abu Ubaidah died in 639 due to plague, which also cost the life of 25,000 Muslims in Syria. After the plague had weakened in late 639 Umar visited Syria for political and administrative re-organization, as most of the veteran commanders and governors had died of plague.

Assassination

, Medina. The first window from the right gives a view of Umar's grave.]] In 644, at zenith of his power, Umar was assassinated. His assassination was carried out by Persians, in response to the Muslim conquest of Persia. The assassination was planned several months earlier. In October 644 Umar went for Hajj in Mecca, the assassins started the hoopla of Umar's possible death that year, and the massive crowd of the congregation was used by the conspirators as a veil to hide themselves. It is related that when Umar stood at Mount Arafat he heard a voice saying:

A companion of Umar, Jabir bin Mutaam is reported to have said:

During one of rituals of Hajj, the Ramy al-Jamarat (stoning of the Devil), some one threw a stone on Umar that wounded his head, a voice was heard that Umar will not attend the Hajj ever again. Amongst the conspirators was: # Hormuzan, the alleged mastermind of the plot. He was Persian Commander in Chief and was captured and brought to Umar at Madinah where to save his life he apparently converted to Islam. # One of Umar's advisors, Ka'ab al-Ahbar, a former Jewish Rabbi, who apparently had converted to Islam, but his conversion is generally doubted by the Shi'ite scholars. # Jafinah, the Christian Arab from Iraq, who was also a foster brother of Saad ibn Abi Waqqas, former governors of Busra. # Piruzan, popularly known as Abu Lulu, he was slave of Mughira ibn Shu'ba the then governor of Busra.

It was Abu Lulu who was assigned the mission of assassinating Umar. According to the plan, before the Fajrprayers (the morning prayers before the dawn) Abu Lulu will enter Al-Masjid al-Nabawi, the main mosque of Madinah where Umar led the prayers and will attack Umar during the prayers, and will flee or will mix with the congregation at mosque. There were Persian children slaves in Madina. Seeing them, Firoz is quoted saying:

Abu Lulu brought a conjectural complaint to Umar about the high tax charged from him by his master Mughirah. Umar wrote to Mughirah and inquired about the tax, Mughirah's reply was satisfactory Umar held that the tax charged from Abu Lulu was reasonable, owning the to his daily income. Umar than is reported to have asked Abu Lulu:

On 3 November 644, Umar was attacked, while leading the morning prayers, Abu Lulu stabbed him six times in the belly and last on the navel, that proved fatal. Umar was left profusely bleeding while Abu Lulu tried to flee but people from all sides rushed to capture him, he in his efforts to escape is reported to have wounded twelve other people, six or nine of them later died. At last he was captured but committed suicide from the same dagger. Umar died of the wounds three days later on Sunday, 7 November 644. Umar is reported to have left the following testament:

As per Umar's will, he was buried next to Al-Masjid al-Nabawi alongside Muhammad and Caliph Abu Bakr by the permission of Aisha.

Aftermaths

On his death bed Umar vacillated to appoint his successor, however it has been reported that he said that if Abu Ubaidah ibn al-Jarrah, Khalid ibn Walid or Salim, the mawali and freed Persian slave, were alive he would have appointed one of them his successor. Umar finally appointed a committee of six persons comprising, #Abdur Rahman bin Awf #Saad ibn Abi Waqqas #Talha ibn Ubaidullah #Uthman ibn Affan #Ali ibn Abi Talib #Zubayr ibn al-Awwam

Their task was to chose a caliph from amongst them. Umar appointed a band of fifty armed soldiers to protect the house where the meeting was proceeding. Until the appointment of the next caliph Umar appointed a notable Sahabi, a mawali, Suhayb ar-Rumi (Suhayb the Roman) as a caretaker Caliph. While the historic meeting for selection of caliph was preceding, Abdulrehman ibn Abu Bakr and Abdur Rahman bin Awf revealed that they saw the dagger used by Abu Lulu, the assassin of Umar. A night before Umar's assassination, reported Abdur Rahman bin Awf, he saw Hormuzan, Jafina and Abu Lulu, while they were suspiciously discussing some thing, bewildered by his presence, the dagger fell, it was the same two sided dagger used in the assissination. Abudulrehman ibn Abu Bakr, son of late caliph Abu Bakr also confirmed that few days before Umar's assassination, he once saw this dagger with Hurmazan. After the mystery of assassination got uncovered by the two of the most notable governmental figures, it seemed clear that the assassination was planned by the Persians residing in Medina. Infuriate by this Umar's younger son Ubaidullah ibn Umar sought to kill all the Persians in Madinah. He killed Hormuzan, Jafinah, and daughter of Umar's assassin Abu Lulu, who is believed to be a Muslim. Ubaidullah was intercepted by the people of Madinah and withholding him from the massacre. Amr ibn al-Aas is said to have intercepted him, convinced him to handover his sword. The murder of Jafinah, enraged Saad ibn Abi Waqqas, his foster brother, and he assaulted Ubaidullah ibn Umar and again the companions intervened. It is also believed that Umar daughter Hafsa bint Umar provoked Ubaidullah to take the punitive action. When Umar was informed about the incident, he ordered that Ubaidullah should be imprisoned and the next Caliph should decide his fate. Umar died on 7 November 644; on 11 November Uthman succeeded him as the Caliph. After prolonged negotiations the tribunal decided to give blood money to the victims and released Umar's son Ubaidullah, on the ground that after the tragic incident of Umar's assassination people will be further infuriated by execution of his son the very next day.

Legacy

Umar is regarded as one of the most influential figures in Islamic history. He was in a true sense the architect of the Islamic Empire. As a leader, 'Umar was known for his simple, austere lifestyle. Rather than adopt the pomp and display affected by the rulers of the time, he continued to live much as he had when Muslims were poor and persecuted. 'Umar was vigorous, robust and a very tall man, in markets he would tower above the people. The front part of his head was bald, always A'sara Yusran (working with two hands), both his eyes are black, with yellow skin, however, ibn Sa'ad in his book The Book of the Major Classes (Tabaqat al-Kubra) stated that he never knew that 'Umar had yellow skin, except if the people took into criterion a certain part of his life where his color changed because he always ate oil at that part of his life,

Humility

In his book Encyclopaedia of Islam, Mufti Muhammad Mukarram Ahmed describes his journey to Jerusalem to take control of the city from the Byzantine Patriarch of Jerusalem Sophronius:

In The Decline and Fall of the Roman Empire, Gibbon refers to Umar in the following terms:

Political legacy

Umar is considered as a political genius, as an architect of Islamic Empire he is regarded as 52nd most influential figure in history. Umar remained politically stagnant during Prophet Mohammad's era, however after his death, it was Umar's political brilliance that Abu Bakr was elected Caliph, despite of massive initial confrontations at Saqifah, Umar successfully broke the alliance of the tribes of Madinah who claim Caliphate to be their right, paving the way for the succession of Abu Bakr. During Abu Bakr's era, he actively participated as his secretory and main adviser. After succeeding Abu Bakr as caliph, Umar win over the hearts of Baudouin tribes by emancipating all their prisoners and slaves taken during Ridda wars, his excellent oratory skills helped him to heightened his popularity graph, mostly among the poor and underprivileged people. He proved himself as a excellent manager during the year of the great Famine when his dynamic abilities saved millions from starvation. He is best known to built up an efficient administrative structure of the empire, that held together his vast realm. He organized an effective network of intelligence, partly a reason for his strong grip on his bureaucracy. His judicial reforms were fairly modern and advance in nature when compared to contemporary systems of his era. He opposed the construction of present day Suez Canal, as it posed threat to the security of Madinah. Twelve hundred years later Great Britain opposed the construction of the canal for the same reason as it then posed threat to its colonies in Indian subcontinent. One of the reason of the compactness of his political rule in the conquered lands is reputed to his policy of tolerance to their religious believes and imposition of far lower taxes on them as compared to Sassanid Persian empire and Byzantine Empire. Their local administration was kept un-touched and several of the former Byzantine and Persian official were retained on their services under Umar's governors. Umar was very painstaking in every matter. His meticulous was evident from his appointment of governors and judges that never let him lose his grip on the government. He never appointed governors for more than two years, for they might get influence in their county. He dismissed his most successful general Khalid ibn Walid, due to his immense popularity and growing influence that he saw menace to his authority. Rather than tenacious conquest he stressed more on consolidating his rule in the conquered land, a fact that saved Byzantine empire from complete disappearance. Umar is reported to have wished an official tour across his domain to personally examine the condition of his subjects. In 641, before the conquest of Persian empire, Umar is reported to have said:

At the time, Umar made this statement, Persia was not yet conquered (conquest of Persia begun in 642). He would walk the streets of Medina with a whip in his hand, and it is said that Umar's whip was feared more than the sword of another man. He is famous for covert night tour of the city to know the secret life of his domain, the tradition that later be followed by some of the Abbasid Caliphs and even Mughul rulers of Indian subcontinent.

Social justice and accountability

Saeed M Mohtsham cites from Caliph Umar's rule in his research paper Vision and Visionary Leadership – An Islamic Perspective:

Military legacy

It has been reported that Umar was a champion wrestler of his time, and though not distinguished as a swordsman, he would later attain prominence as a master strategist. Along with Khalid, he is said to be one of the key figures in the collapse of the Arabian rebellion, the greatest triumph of Abu Bakr. One of his greatest strategic marvels was his brilliant fission of Persio-Roman alliance in 636, when Emperor Heraclius and Emperor Yazdegerd III allied against their common enemy Umar. He was lucky in that the Persian Emperor Yazdegerd III couldn't synchronize with Heraclius as planned. Umar fully availed the opportunity and successfully tackled the minefield by straining the Byzantines to jump in the battle. This was contrary to the orders of Empreror Heraclius, who presumably wanted a coordinated attack along with the Persians. Umar did this by sending reinforcements to the Roman front with instructions that they should appear in the form of small bands, one after the other, giving the impression of a continuous stream of reinforcements that finally lured the Byzantines to an untimely battle. On the other hand Yazdegerd III of Persia was engaged in negotiations that further gave Umar time to transfer his troops from Syria to Iraq. These troops proved decisive in the Battle of Qadisiyyah. Both the battles thus fought proved decisive and are noted as two of the most decisive battles in history.

His strategic dimensions were the prime reason of Muslim victory at 2nd Battle of Emesa in 638. Where the pro-Byzantine Christian Arabs of Jazira, aided by Byzantine Emperor, making an unexpected flanking movement and laid siege to Emesa (Homs). Umar's brilliance was behind this Muslim victory and was achieved without firing a single shot.

Umar's orders to invade the very homeland of the Christian Arab forces besieging Emesa, the Jazirah. A three prong attack against Jazirah was launched from Iraq. To further pressurize the Christian Arab armies, Umar instructed Saad ibn Abi Waqqas, commander of Muslim forces in Iraq, to sent reinforcement to Emesa, Umar himself led a reinforcement from Madinah and marched towards Emesa. Under this unprecedented press-gang, Christian Arabs retreated from Emesa before Muslims reinforcement could reach their. This incursion from Byzantines however resulted in Muslim annex Mesopotamia and parts of Byzantine Armenia.

Nonetheless the greatest triumph of Umar remained Conquest of Persian empire. After years of non-offensive policy according to which Umar wished the Zagros Mountains to be the frontiers between Muslims and Persians, after Battle of Nahavand Umar launched a whole scale invasion of Sassanid Persian Empire. The invasion was a series of well coordinated multi-prong attacks that was based on the principle of isolating and then destroying the target. Umar launched the invasion by attacking the very heart of Persia aiming to isolate Azerbaijan and eastern Persia. It was immediately followed by simultaneous attacks on Azerbaijan and Fars. In the final secession Sistan and Kirman and captured thus isolating the stronghold of Persian, the Khurasan. The final expedition was launched against Khurasan where after Battle of Oxus river Persian empire ceased to exist, and emperor Yazdegerd III fled to Central Asia. He founded the city of Cairo, conquered 36,000 cities or castles, and built 1400 mosques.

Religious legacy

Sunni views

Sunnis remember Umar as a rigid Muslim of a sound and just disposition in matters of the religion of Allah, a man they title Farooq, meaning "leader, jurist and statesman", and the second of the rightly-guided Caliphs. He patched his clothes with skin, took buckets on his two shoulders, always riding his donkey without the saddle, rarely laughing and never joking with anyone. On his ring is written the words "Enough is Death as a reminder to you O' 'Umar". He did not seek advancement for his own family, but rather sought to advance the interests of the Muslim community, the ummah. The general Sunni sentiment for Umar is summarized by one of Muhammad's companions, Abd Allah ibn Mas'ud:

Shia views

Umar is viewed very negatively in Shi'a literature and is regarded as a traitor to Muhammad, a usurper of Ali's rights, and a murderer. According to shia, his role during Muhammad's life time is questioned as he was not assigned to any civil or military authority. Some Shi'a writers have accused him of killing Muhammad's daughter Fatimah (see Fatimah's death). According to Shia Muslims, Fatimah, wife of Ali and daughter of Muhammad, was physically abused by him. These sources report that the event caused her to miscarry her child and eventually led to her death soon after. (see Umar at Fatimah's house).

Western views

In his book Mahomet and His Successors, Washington Irving estimates the achievements of Umar in the following terms:

In his book Sir William Muir says as follows about Umar:

In The Decline and Fall of the Roman Empire, Gibbon refers to Umar in the following terms:

In his book History of the Arabs Professor Philip Khuri Hitti has assessed the achievements of Umar in the following terms:

Encyclopedia Britannica remarks about Umar:

On the other hand, David Samuel Margoliouth offers this assessment of Umar:

"Yet we have no record of any occasion on which Omar displayed remarkable courage, though many examples are at hand of his cruelty and bloodthirstiness; at the battle of Hunain he ran away, and on another occasion owed his life to the good nature of an enemy." (Mohammed and the Rise of Islam, pg 164)"

However, in contrast to Margoliouth's assertion, Shahid Ashraf in his literary work Encyclopaedia of Holy Prophet and Companions celebrates Umar as amongst the firmest companions who remained with the Prophet Muhammad at his most critical juncture during the battle of Hunain when others fled during ther disarray:

This view of Umar's courageous commitment at the Battle of Hunayn is also shared by Mufti Muhammad Mukarram Ahmed, the famed Ibn Ishaq in his Sīrat rasūl Allāh, Masudul Hasan in Hadrat Ali Murtada. In fact, the famed Ibn Sa'd's Kitab al-Tabaqat al-Kabir, one of the most reliable works of Islamic history, it is reported: "On that day (Battle of Hunayn) those (few) who remained firm were al-Abbas, Ali ibn Abi Talib, ... Abu Bakr, Umar, ..."

Family

Umar married a total of 9 women in his lifetime and had 14 children, 10 sons and 4 daughters.

The details are as follow:

::Wife: Zaynab bint Mazh'un (at the time of Jahiliyyah [Days of Ignorance]) :::Son: Abdullah ibn Umar :::Son: Abdulrahman ibn 'Umar (The Older) :::Son: Abdulrahman ibn 'Umar :::Daughter: Hafsa bint Umar ::Wife: Umm Kulthum bint Jarwila Khuzima (divorced) :::Son: Ubaidullah ibn Umar :::Son: Zayd ibn 'Umar :::Daughter: Fatima bint 'Umar ::Wife: Jamilah bint Ashim ibn Thabit ibn Abi al-Aqlah (from the tribe of Aws) :::Son: Asim ibn Umar ::Wife: Atikah bint Zayd ibn Amr ibn Nifayl (cousin of Umar and former wife of Abdullah ibn Abu Bakr married 'Umar in the year 12 AH and after 'Umar was murdered, she married az-Zubayr ibn al-Awwam) :::Son: Iyaad ibn 'Umar ::Wife: Umm Kulthum bint 'Ali (the daughter of Ali ibn Abi Talib). :::Son: Zayd ibn 'Umar, (famously known as Ibnul Khalifatayn; the son of the two Caliphs i.e Umar and Ali). :::Daughter: Ruqayyah bint 'Umar ::Wife: Luhyah (a woman from Yemen (Yaman) who's marital status with 'Umar is disputed, al-Waqidi said that she was Umm Walad, meaning a slave woman) :::Son: Abdulrahman ibn 'Umar (the youngest Abdulrehman while some say the middle Abdulrehman from Luhyah) ::Wife: Fukayhah (as Umm Walad) :::Daughter: Zaynab bint 'Umar (the smallest child of 'Umar from Fukayhah) Another son is, az-Zubayr ibn Bakkar, called Abu Shahmah, though from which wife is unknown.

See also

Ali

Abu Bakr

Uthman

Sunni view of the Sahaba

Sunni view of Umar

Ahadith on virtues of Abu Bakr

Hadiths on virtues of Umar bin Khattab

Ahadith on virtues of Uthman bin Affan

Ahadith on virtues of Ali bin Abu Talib

Dhikr

Al Haleem

Notes

References

Donner, Fred, The Early Islamic Conquests, Princeton University Press, 1981.

Guillaume, A., The Life of Muhammad, Oxford University Press, 1955.

Hourani, Albert, A History of the Arab Peoples, Faber and Faber, 1991.

Madelung, Wilferd, The Succession to Muhammad, Cambridge University Press, 1997.

"G.LeviDellaVida and M.Bonner "Umar" in Encyclopedia of Islam CD-ROM Edition v. 1.0, Koninklijke Brill NV, Leiden, The Netherlands 1999"

Previte-Orton, C. W (1971). The Shorter Cambridge Medieval History. Cambridge: Cambridge University Press.

How Many Companions Do You Know? By Ali Al-Halawani

External links

Excerpt from The History of the Khalifahs by Jalal ad-Din as-Suyuti

Sirah of Amirul Muminin Umar Bin Khattab (r.a.a.) by Shaykh Sayyed Muhammad bin Yahya Al-Husayni Al-Ninowy.

Category:588 births Category:644 deaths Category:644 crimes Category:Converts to Islam Category:Arab people Category:Rashidun Category:Sahaba Category:Assassinated caliphs Category:7th-century caliphs