Pengenalan Kepada Sistem Pancitan Bahan Api Elektronik (EFI)Suntikan bahan api atau pancitan bahan api adalah sistem kenderaan yangbertugas mengangkut bahan api ke kenderaan selain daripadapenggunaan karburetor. Dua jenis suntikan bahan api yang paling lazimadalam sistem suntikan bahan api petrol dan diesel. Suntikan bahan apimembawa bahan api bertekanan tinggi dan menyemburkannya menjadi titisanhalus ke ruang rongga masukan (bagi kes enjin petrol) ataupun secara teruske dalam kebuk pembakaran (bagi kes enjin diesel) untuk menambah luaspermukaan cecair bahan api bagi pembakaran yang lebih cekap. Sebelum ini,kebanyakan enjin petrol menggunakan karburetor tetapi sekarang bolehdikatakan hampir kesemua model kereta terkini menggunakan suntikanbahan api manakala karburetor hanya digunakan pada enjin-enjin yang kecilseperti pada motosikal.Perbezaan fungsi yang paling ketara antara karburetor dan suntikan bahan apiialah suntikan bahan api menyembur bahan api kepada titisan yang sangathalus dengan mengepam bahan api secara paksaan ke muncung halus dibawah tekanan tinggi, sementara karburetor pula bergantung kepada tekananvakum oleh udara masukan untuk menghantar bahan api.Pemancit bahan api hanya terdiri daripada sebuah muncung serta injap; bahanapi dihantar melalui pam bahan api atau bekas bertekanan  Soalan 3(a)KABURATOR I. Karburator mempunyai 2 paip terbuka dikedua-dua hujungnya, dalam paip ini udara bergerak menuju kedalam ruang pembakaran. Paip ruang pembakaran ini berbentuk venturi, iaitu lebar pada kedua-dua hujung dan berbentuk sempit di bahagian tengah.Rekabentuk ini mempercepatkan aliran udara semasa melalui venturi.II. Pada satu hujung venturi terdapat penutup udara berbentuk kupu-kupu yang berfungsimengawal aliran udara. Nilai isipadu udara dan isipadu bahan bakar menentukan jumlah tenaga yang dikeluarkan seterusnya menetukan kalajuan sesuatu motor. Pedalminyak dihubungkan melalui kabel dengan penutup udara.III. Pedal minyak juga dihubungkan dengan piston yang mengatur saiz dalam venturi.IV. Bahan bakar atau minyak dialirkan ke saluran udara melalui saluran-saluran kecil yangterdapat dalam ruang sempit dalam venturi.V. Udara yang bergerak masuk ke dalam karburator yang akan mewujudkan tekananuntuk menarik serta bahan bakar masuk kedalam ruang pembakaran

Prinsip Kerja Karburator

Karburator adalah komponen penting kendaraan, baik sepeda motor maupun mobil yang berbahan bakar bensin (mesin Otto). Berfungsi untuk mencampur bahan bakar dengan udara sebelum masuk ruang bakar pada Internal Combustion Engine. Meskipun sekarang sudah mulai tergantikan

oleh sistem Injeksi yang lebih efisien, namun karburator masih dipilih karena dinilai lebih ekonomis harganya (murah) dan lebih mudah dalam hal maintenance.

Tidak seperti sistem injeksi yang harus pergi ke bengkel resmi untuk menservisnya, karena sistem injeksi lebih banyak dikontrol oleh perangkat elektronik yang harganya juga mahal.

Namun, tahukah kita sebenarnya bagaimana karburator bisa bekerja, sehingga kendaraan kita bisa digunakan sehari-hari?

Karburator bekerja menggunakan prinsip Bernoulli. Semakin cepat aliran udara melewati karburator, tekanan statisnya akan menurun, sebaliknya tekanan dinamis akan meningkat.

Tarikan handle gas pada sepeda motor atau pedal gas pada mobil hanya berfungsi untuk mengatur bukaan throttle. Besar-kecilnya bukaan throttle inilah yang mengendalikan jumlah aliran udara yang bisa masuk ke ruang bakar melewati karburator. Aliran udara yang melewati karburator ini membuat tekanan statis menurun, sehingga bahan bakar bisa naik dari mangkuk karburator dan tercampur dengan udara hingga akhirnya masuk ke dalam ruang bakar.

Sebelum masuk ke ruang bakar, campuran udara dengan bahan bakar melewati intake manifold yang berfungsi untuk menyalurkan kabut (udara + bahan bakar) agar bisa sampai di ruang bakar. Di ruang bakar inilah akhirnya energi kimia yang terkandung dalam bahan bakar dikonvesikan menjadi energi gerak piston.

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Prinsip Kerja Karburator

Karburator adalah komponen penting kendaraan, baik sepeda motor maupun mobil yang berbahan bakar bensin (mesin Otto). Berfungsi untuk mencampur bahan bakar dengan udara sebelum masuk ruang bakar pada Internal Combustion Engine. Meskipun sekarang sudah mulai tergantikan oleh sistem Injeksi yang lebih efisien, namun karburator masih dipilih karena dinilai lebih ekonomis harganya (murah) dan lebih mudah dalam hal maintenance.

Tidak seperti sistem injeksi yang harus pergi ke bengkel resmi untuk menservisnya, karena sistem injeksi lebih banyak dikontrol oleh perangkat elektronik yang harganya juga mahal.

Namun, tahukah kita sebenarnya bagaimana karburator bisa bekerja, sehingga kendaraan kita bisa digunakan sehari-hari?

Karburator bekerja menggunakan prinsip Bernoulli. Semakin cepat aliran udara melewati karburator, tekanan statisnya akan menurun, sebaliknya tekanan dinamis akan meningkat.

Tarikan handle gas pada sepeda motor atau pedal gas pada mobil hanya berfungsi untuk mengatur bukaan throttle. Besar-kecilnya bukaan throttle inilah yang mengendalikan jumlah aliran udara yang bisa masuk ke ruang bakar melewati karburator. Aliran udara yang melewati karburator ini membuat tekanan statis menurun, sehingga bahan bakar bisa naik dari mangkuk karburator dan tercampur dengan udara hingga akhirnya masuk ke dalam ruang bakar.

Sebelum masuk ke ruang bakar, campuran udara dengan bahan bakar melewati intake manifold yang berfungsi untuk menyalurkan kabut (udara + bahan bakar) agar bisa sampai di ruang bakar. Di ruang bakar inilah akhirnya energi kimia yang terkandung dalam bahan bakar dikonvesikan menjadi energi gerak piston.

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hich offers the best performance, carburetor or fuel injection, is highly debated question among car enthusiasts. Many believe that performance is best with a carburetor while others insist that the only way to go is with fuel injection gasoline. To determine which is best for your vehicle, it's important to understand how both components work.

Engine Performance

The carburetor and fuel injection performance is mainly due to the amount of air and gasoline that can enter into the engine cylinders. The cylinders contain the pistons and combustion chambers where energy is released from the combustion of gasoline. The carburetor and fuel injection system will both feed fuel and air into the engine.

The Carburetor

The carburetor contains jets that will push the gas into the combustion chambers. The amount of fuel that can flow through these jets depends completely on the amount of air that can be pulled into the carburetor venture. The main issue with obtaining the best performance using a carburetor is that it can't monitor the air to fuel ratio for each individual cylinder. If there was a carburetor for each cylinder then this would not be an issue. So with a carburetor, the best fuel to air ratio for each cylinder is approximated for the best performance. However, carburetors do last longer than fuel injection systems and are favored in motor sports. Carburetors are also much simpler to install than fuel injection systems, because there are no electrical components or return lines to the fuel tank. The carburetor is currently much less expensive than the electronic fuel injection systems.

Fuel Injection Systems

Fuel injection systems are becoming more popular for those wanting the best performance from their engines. There are two different versions of fuel injection - port fuel injection and direct injection. Port fuel injection is the most commonly used and direct fuel injection is the latest developed fuel injection system. This system was designed specifically for four or two stoke engines. The main benefits to using direct injection is that the amount of fuel and air can be

perfectly released and then injected into the cylinder according to the engine load conditions. The electronics used in the system will calculate this information and constantly adjust. This type of controlled fuel injection results in a higher power output, greater fuel efficiency and much lower emissions. One of the main issues is that these systems are sophisticated and will cost much more than a carburetor. Installation is more complicated as it uses an electrical component and custom cylinder head configuration.

Which Is Best?

It is fairly obvious that most automobiles will be changing to fuel injection systems due to the lower emissions. However, unless the cost of these systems decreases significantly then there will still be a massive following that will stick to carburetors. When looking at pure horsepower, the fuel injection system only delivers about 10 extra horsepower at peak. It is the ability to constantly be tuning the fuel and air intake for each cylinder that benefits the performance. The fuel injection systems are the best as they will decrease vibration and help to overcome steep grades that are traditional terrain for off-roading. Again, which one is best completely depends on where and how you're driving.

echanical fuel injection is used to indicate the metering functions of the fuel injection system. Carburetor fuel injection is an advancement of the mechanical fuel injection method. The aim of all types of fuel injections systems is to achieve a delivery of the exact air/fuel mix into the combustion engine. All the types of fuel injections try to force the fuel into the combustion engine under a great pressure through injectors. Fuel injectors provide good mileage and power improvements over RPM range of the engine.

Features of Mechanical Fuel Injection

All the fuel injection systems which may be a mechanical system or an EFI system follow only mechanical operations in order to force fuel into an engine. The difference is that the EFI system performs various on and off operations electronically, which are due to a variety of electronic controls present within the EFI system. These tell how and when the fuel must be injected into the engine. This facility is not available in the mechanical fuel injection system.

The optimum ratio of air to fuel varies with the changes occurring in the atmospheric temperature, engine temperature, altitude, engine load and speed, ignition timings, and the gasoline engines. So the fuel injections must be designed in such a way that it must adjust to the engine requirements. Hence the fuel injection system must be able to sense the variations in these parameters. Microprocessors are used in order to serve this purpose. These microprocessors compute whether the correct amount of fuel is injected when it is required or not adjusting to the requirements of the engine.

Usage of Mechanical Fuel Injection

Carburetors were used until 1980 because they are inexpensive, and were consumer friendly. Being frequently used in petrol or gasoline engines. Fuel injection and precision pumps were also used at that time, but were very costly. Hence carburetors became the alternative.

Also, they were incorporated into the engines such as Mopar and GM vehicles. But these became obsolete by the emergence of electronic fuel injection systems. Many American systems were not fully understood and proved to be very unreliable. Consumers switched quickly for the added value, reliability, and merely a more culturally appropriate device enjoyed in carburetors. Then a number of European systems came into existence.

Historically, mechanical injection systems were used only for racing cars and land speed records during 1950 and 1960. Hilborn and Enderle were 2 of the early innovators. This technology was utilized because EFI systems were not culturally relevant and difficult for consumer adaptation. It involved numerous electronic interventions.

EFI and Mechanical Fuel Injection

An EFI injector has special valves which open and close for fuel to enter the engine. They are electronically controlled. EFI sprays the fuel into the open valves in the form of a mist which is very fine. The valves are opened and closed alternatively in order to push the fuel inside. The injector also checks how much fuel is injected into it by a fuel track.

The special feature of EFI fuel injection is that it operates through mechanical sensors within the system. Sensors are included to ensure that the exact amount of fuel is injected at the specific time.

This is a bizarre description which doesn't quite cover the point.

Mechanical fuel injection took off in the 1970s. Bosch's K-Jetronic system was used on such ubiquitous vehicles as the VW Rabbit-Scirocco-Golf and the Volvo 140/240, and it can hardly be considered rare or unusual, let alone a racing-only type thing.

Curiously, EFI was in common use EARLIER than mechanical injection was. Bosch's D-Jetronic system was used on many VWs and Volvos, among others, starting around 1969-1971. D-Jet was a proper multiport EFI system and performed well... when it was working. It was rather ambitious to create a pure EFI system in 1970, and the system wasn't ready for prime time... it was rather finicky and impractical for a daily driver.

K-Jet may seem like a step backward in that it was, at its heart, a pure mechanical system. The "mass air flow sensor" consisted of a metal plate which was moved upward by air passing through to the engine. The plate was on a lever arm that operated a valve-like control... As the air pushed the plate higher the valve would open and let more fuel in. Pure simplicity. Later implementations of K-Jet included some electronic add-ons to fine-tune the mixture and idle speed on the fly, even including oxygen sensors, but the mechanical heart of the system was still there. The K-Jetronic mechanical injection system was highly reliable and flexible, and a big step up from the carburetors of the 1970s. It finally fell out of fashion when the more precise, true multiport EFI systems became reliable... and the throttle-body EFI systems became cheap.

"Cultural acceptance" was not the only reason for the switch to fuel injection. The greater burn efficiency of fuel injection meant lower emissions without having to de-tune the motor. As emissions requirements grew more stringent, carbureted vehicles grew less and less powerful while fuel injected cars actually gained power and efficiency. By the late 1970s, the MGB sports car had become less powerful than the EFI Volkswagen, which was embarrassing. So, fuel injection became a "requirement" in the 1980s as it was simply impossible to get both high performance and low emissions out of a carburetor.

Mechanical fuel injection took off in the 1970s. Bosch's K-Jetronic system was used on such ubiquitous vehicles as the VW Rabbit-Scirocco-Golf and the Volvo 140/240, and it can hardly be considered rare or unusual, let alone a racing-only type thing.

Curiously, EFI was in common use EARLIER than mechanical injection was. Bosch's D-Jetronic system was used on many VWs and Volvos, among others, starting around 1969-1971. D-Jet was a proper multiport EFI system and performed well... when it was working. It was rather ambitious to create a pure EFI system in 1970, and the system wasn't ready for prime time... it was rather finicky and impractical for a daily driver.

K-Jet may seem like a step backward in that it was, at its heart, a pure mechanical system. The "mass air flow sensor" consisted of a metal plate which was moved upward by air passing through to the engine. The plate was on a lever arm that operated a valve-like control... As the air pushed the plate higher the valve would open and let more fuel in. Pure simplicity. Later

implementations of K-Jet included some electronic add-ons to fine-tune the mixture and idle speed on the fly, even including oxygen sensors, but the mechanical heart of the system was still there. The K-Jetronic mechanical injection system was highly reliable and flexible, and a big step up from the carburetors of the 1970s. It finally fell out of fashion when the more precise, true multiport EFI systems became reliable... and the throttle-body EFI systems became cheap.

"Cultural acceptance" was not the only reason for the switch to fuel injection. The greater burn efficiency of fuel injection meant lower emissions without having to de-tune the motor. As emissions requirements grew more stringent, carbureted vehicles grew less and less powerful while fuel injected cars actually gained power and efficiency. By the late 1970s, the MGB sports car had become less powerful than the EFI Volkswagen, which was embarrassing. So, fuel injection became a "requirement" in the 1980s as it was simply impossible to get both high performance and low emissions out of a carburetor

The Fall of the Carburetor

For most of the existence of the internal combustion engine, the carburetor has been the device that supplied fuel to the engine. On many other machines, such as lawnmowers and chainsaws, it still is. But as the automobile evolved, the carburetor got more and more complicated trying to handle all of the operating requirements. For instance, to handle some of these tasks, carburetors had five different circuits:

Main circuit - Provides just enough fuel for fuel-efficient cruising Idle circuit - Provides just enough fuel to keep the engine idling

Accelerator pump - Provides an extra burst of fuel when the accelerator pedal is first depressed, reducing hesitation before the engine speeds up

Power enrichment circuit - Provides extra fuel when the car is going up a hill or towing a trailer

Choke - Provides extra fuel when the engine is cold so that it will start

In order to meet stricter emissions requirements, catalytic converters were introduced. Very careful control of the air-to-fuel ratio was required for the catalytic converter to be effective. Oxygen sensors monitor the amount of oxygen in the exhaust, and the engine control unit (ECU) uses this information to adjust the air-to-fuel ratio in real-time. This is called closed loop control -- it was not feasible to achieve this control with carburetors. There was a brief period of electrically controlled carburetors before fuel injection systems took over, but these electrical carbs were even more complicated than the purely mechanical ones.

At first, carburetors were replaced with throttle body fuel injection systems (also known as single point or central fuel injection systems) that incorporated electrically controlled fuel-injector valves into the throttle body. These were almost a bolt-in replacement for the carburetor, so the automakers didn't have to make any drastic changes to their engine designs.

Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection (also known as port, multi-point or sequential fuel injection). These systems have a fuel injector for each cylinder, usually located so that they spray right at the intake valve. These systems provide more accurate fuel metering and quicker response.

Mechanical injection

In the 1940s, hot rodder Stuart Hilborn offered mechanical injection for racers, salt cars, and midgets.[5]

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 the 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.

The 1954 Mercedes-Benz W196 Formula 1 racing car engine used Bosch direct injection derived from wartime aero engines. The same engine was used in the Mercedes-Benz 300SLR famously driven by Stirling Moss to victory in the 1955 Mille Miglia.

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 that 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 a "port" injection where the injectors are located in the intake manifold, very near the intake valve.

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.[6] These racing-derived systems were not suitable for everyday street use, having no provisions for low speed metering, or often none even for starting (starting required that fuel be squirted into the injector tubes while cranking the engine). However they were a favorite in the aforementioned competition trials in which essentially wide-open throttle operation was prevalent. Constant-flow injection systems continue to be used at the highest levels of drag racing, where full-throttle, high-RPM performance is key.[7]

Another mechanical system, made by Bosch called Jetronic, but injecting the fuel into the port above the intake valve, was used by several European car makers, particularly Porsche from 1969 until 1973 in the 911 production range and until 1975 on the Carrera 3.0 in Europe. Porsche

continued using this system 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 early Bosch Jetronic systems were also used by Audi, Volvo, BMW, Volkswagen, and many others. 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 that was used by some Maserati, Aston Martin, and Triumph models between 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 U.S. market 1750 and 2000 models from 1969 to 1981. This was designed to meet the U.S. emission requirements with no loss in performance and it also reduced fuel consumption.

Electronic injection

The first commercial electronic fuel injection (EFI) system was Electrojector, developed by the Bendix Corporation and was offered by American Motors Corporation (AMC) in 1957.[8][9] The Rambler Rebel, showcased AMC's new 327   cu   in (5.4   L) engine . The Electrojector was an option and rated at 288 bhp (214.8 kW).[10] The EFI produced peak torque 500 rpm lower than the equivalent carburetored engine[6] The Rebel Owners Manual described the design and operation of the new system.[11] (due to cooler, therefore denser, intake air[citation needed]). The cost of the EFI option was US$395 and it was available on 15 June 1957.[12] Electrojector's teething problems meant only pre-production cars were so equipped: thus, very few cars so equipped were ever sold[13] and none were made available to the public.[14] The EFI system in the Rambler ran fine in warm weather, but suffered hard starting in cooler temperatures.[12]

Chrysler offered Electrojector on the 1958 Chrysler 300D, DeSoto Adventurer, Dodge D-500 and Plymouth Fury, arguably the first series-production cars equipped with an EFI system. It was jointly engineered by Chrysler and Bendix. The early electronic components were not equal to the rigors of underhood service, however, and were too slow to keep up with the demands of "on the fly" engine control. Most of the 35 vehicles originally so equipped were field-retrofitted with 4-barrel carburetors. The Electrojector patents were subsequently sold to Bosch.

Bosch developed an electronic fuel injection system, called D-Jetronic (D for Druck, German for "pressure"), which was first used on the VW 1600TL/E in 1967. This was a speed/density system, using engine speed and intake manifold air density to calculate "air mass" flow rate and thus fuel requirements. This system was adopted by VW, Mercedes-Benz, Porsche, Citroën, Saab, and Volvo. Lucas licensed the system for production with Jaguar. Bosch superseded the D-Jetronic system with the K-Jetronic and L-Jetronic systems for 1974, though some cars (such as the Volvo 164) continued using D-Jetronic for the following several years. In 1970, the Isuzu 117 Coupé was introduced with a Bosch-supplied D-Jetronic fuel injected engine sold only in Japan.

Chevrolet Cosworth Vega engine showing Bendix electronic fuel injection (in orange).

The Cadillac Seville was introduced in 1975 with an EFI system made by Bendix and modelled very closely on Bosch's D-Jetronic. L-Jetronic first appeared on the 1974 Porsche 914, and uses a mechanical airflow meter (L for Luft, German for "air") that produces a signal that is proportional to "air volume". This approach required additional sensors to measure the atmospheric pressure and temperature, to ultimately calculate "air mass". L-Jetronic was widely adopted on European cars of that period, and a few Japanese models a short time later.

In Japan, the Toyota Celica used electronic, multi-port fuel injection in the optional 18R-E engine in January 1974.[15] Nissan offered electronic, multi-port fuel injection in 1975 with the Bosch L-Jetronic system used in the Nissan L28E engine and installed in the Nissan Fairlady Z, Nissan Cedric, and the Nissan Gloria. Toyota soon followed with the same technology in 1978 on the 4M-E engine installed in the Toyota Crown, the Toyota Supra, and the Toyota Mark II. In the 1980s, the Isuzu Piazza, and the Mitsubishi Starion added fuel injection as standard equipment, developed separately with both companies history of diesel powered engines. 1981 saw Mazda offer fuel injection in the Mazda Luce with the Mazda FE engine, and in 1983, Subaru offered fuel injection in the Subaru EA81 engine installed in the Subaru Leone. Honda followed in 1984 with their own system, called PGM-FI in the Honda Accord, and the Honda Vigor using the Honda ES3 engine.

The limited production Chevrolet Cosworth Vega was introduced in March 1975 using a Bendix EFI system with pulse-time manifold injection, four injector valves, an electronic control unit (ECU), five independent sensors and two fuel pumps. The EFI system was developed to satisfy stringent emission control requirements and market demands for a technologically advanced responsive vehicle. 5000 hand-built Cosworth Vega engines were produced but only 3,508 cars were sold through 1976.[16]

The other day one guy quizzed me about the expected fuel efficiency of the KTM 200 Duke. I told him that I can’t tell for sure but it can be expected around the 30 Kmpl figure.

That guy was surprised and told me, “That low..?? But the KTM 200 Duke has Fuel Injection, so why such a low mileage figure?”.

I wouldn’t blame that guy as there are many myths surrounding “Fuel Injection” system. Till a

couple of years back, even I used to think that "Fuel Injection" was a magic pill which elevated a bike's performance dramatically.

Fuel Injection: Myths

Myth 1: Fuel Injection gives a drastic increase in mileage (fuel efficiency)Myth 2: Fuel Injection gives a bump in PowerMyth 3: Fuel Injection gives a much better throttle response than a carburetor

In theory a Fuel Injection system should improve the fuel efficiency, power delivery and throttle response. But after having ridden numerous motorcycles over the years both with carburetor and with Fuel Injection, also having owned a fuel injected motorcycle (Pulsar 220 DTS-Fi), I can tell with conviction that the above benefits of “Fi” are hardly tangible to the rider.

A well tuned carbureted motorcycle also returns equally good fuel efficiency, can deliver same power and once warmed up the engine can feel same in operation.

How a Carburetor Works: In Simple English

A carburetor is a mechanical device which mixes the fuel (petrol) from the fuel tank with air from the atmosphere and sends this mixture to the engine for combustion.

The movement of the piston inside the engine creates a low pressure and this “sucks” the air + fuel mixture inside the engine, which is then ignited for making power.

Advantages:

[+] Cheap to manufacture

[+] Easy to service

[+] Performance modification can be easily done on it

[+] Tolerant to bad quality fuel

[+] Not dependent on a battery / electrical charge

Disadvantages:

[-] Need to apply choke during cold starts and need to warm the engine for a steady idle

[-] Need to adjust the settings when the altitude changes

Fact 1: Fuel Injection is costly

Price differential between a Carbureted and Fuel Injected variant of the same model currently in India is around Rs. 15,000-20,000 (Eg: Carb and Fuel Injected variants of the Hero Glamour, Honda CBF Stunner, TVS Apache RTR 160). As I mentioned earlier, the fuel injected variants hardly give an increment in either power or fuel efficiency despite the price premium.

So why is actually Fuel Injection required?

One upon a time all petrol cars sold in India used to run on Carburetors, currently all petrol cars have shifted to Fuel Injection, so when did this shift happen and most importantly why?

The shift from Carburetor to Fuel Injection in Indian cars started in the mid 90’s and by 2000 nearly every model was running on fuel injection. So, why did this shift happen? Govt. of India was pushing for strict pollution/emission norms, therefore it became impossible for the car manufacturers to comply with the emission norms with carburetors and the only solution was to opt for Fuel injection. I still vividly remember that the cost differential for switching from Carburetor to Fuel Injection in a compact car like the Maruti-Suzuki Zen in the mid 90’s was around Rs. 30,000. The car manufacturers had no option but to swallow the bitter bill and go ahead with the costly tech.

Therefore..

Fact 2: Main benefit of Fuel Injection is conforming to strict pollution/emission norms

But the catch here is that unlike 4 wheelers/cars, 2 wheelers/motorcycles can still conform to the pollution norms set by Govt. of India with a much simpler and cheaper carburetor without the need to go for Fuel Injection and would not require very soon in the near future as well.

After spending a premium for this "costly and clean" technology, isn’t there some tangible benefits to the rider who opts for Fuel Injection on his bike?

There are two tangible benefits..

Fact 3: Fuel Injection gives a hassle free early morning/cold starts and adjusts to change in

altitude automatically

Fuel Injected vehicles (cars and bikes) don’t have a “choke” lever. It doesn’t need one. The electronics and sensors take account of the conditions (amount of oxygen, temperature etc.) and accordingly inject the correct amount of “air+fuel” mixture to the engine every time. For this reason one doesn’t need to worry for cold morning starts and there is no need to warm the engine as well. Also one doesn’t need to worry about changing the “air+fuel” mixture manually (like changing the carburetor setting) when the altitude changes.

From my own of experience of owing a car and motorcycle with Fuel Injection (Pulsar 220 DTS-Fi), I can share that all one needs to do is to switch on the ignition to start the engine with a single crank and just zoom off.. every single time.

How Fuel Injection Works: In Simple English [Photo: World Honda Site]

A Fuel Injection system consists of many components. One of them is a fuel pump which resides inside the fuel tank. This device pumps fuel to the injectors which according to the signal from the ECU "injects" the optium amount of "air + fuel" mixture to the engine.

There are many electronic sensors like oxygen sensor, temperature sensor working with the system which sends signals to the Electronic Control Unit (ECU). The ECU is programmed to work under variety of inputs and conditions. It is the heart of the Fuel Injection system which controls the inputs to the motorcycle for an efficient, clean and hassle free combustion of the "air + fuel" mixture.

It is hardly surprising why a Fuel Injection system is heavy on the pocket.

Advantages:

[+] Very effective in controlling pollution[+] Hassle free cold starts and no need to warm the engine for a steady idle[+] No need to change settings to ride at different altitudes

Disadvantages:

[-] Costly[-] Sensitive to bad quality of fuel[-] Needs specialized equipment for service[-] Always dependent on a battery (with good charge) for operation[-] For Performance modification the ECU would need to be re-programmed..!!

Fuel Injection & Indian motorcycles:

Expecting customers delighted to pay Rs. 15,000 more for fuel injection when the cost of the vehicle is Rs. 60,000 just for hassle free early morning starting would be wishful thinking.

But then there are other type of customers who are ready to buy bikes costing Rs. 1 Lakh (1,00,000) plus. Such a customer I guess would not mind paying a premium for a hassle free ride experience. Personally I would definitely want to have Fuel Injection on my motorcycle.

the carburetor. It is dead, you know; we motorcyclists are just hanging onto the remains until the official death certificate is issued.

There is no question that those traditional fuel-mixers are ancient history, beloved but outdated instruments of another era made obsolete by electronic fuel injection. After all, there hasn’t been a carbureted automobile produced in more than a decade; and with an increasing number of new bikes being equipped with EFI each model year, it won’t be long before the carburetor is discussed only in the past tense among motorcyclists, as well.

That transition, from carburetion to fuel injection, scares the hell out of some people, and not just the ones who like to tinker with their bikes on week-ends. Even a lot of experienced tuners consider fuel injection a new-age intrusion that has unnecessarily complicated what formerly was a simple procedure.

But that’s to be expected: Any time a new technology begins to replace an older one, the high priests of the old way feel threatened. Those of us who learned the tricks of carburetion don’t like to see our hard-earned knowledge become irrelevant. We balk at the

notion of software hotshots, using a whole new language we don’t understand, taking over the task of fuel delivery. Many hot-rodders also fear that once fuel injection becomes universal, engine modification will be impossible. Not true!

Although it seems that fuel injection threatens to take control of fuel mixture out of the user’s hands and put it into those of government emissions regulators, this is not the case. Yes, EFI is becoming the preferred method by which manufacturers can comply with ever-more-stringent exhaust-emissions regulations. But new developments that we’ll discuss in a few minutes are making it simpler to tune fuel injection, and those advances will soon make adjusting the mixture an easier process than it ever was with carburetors.

Actually, when you make a point-by-point comparison between carburetors and fuel injection, EFI seems a much more rational way to deliver fuel into an engine. To understand why, let’s takea quick refresher course in carburetion.

Carburetors are analog devices that deliver fuel in response to variations in intake vacuum. This vacuum arises, as noted by Bernoulli’s famous principle,

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from the fact that as air is set into motion, it trades away some of its pressure to create velocity. The resulting partial vacuum in the venturi of a carburetor is powerful enough to draw up fuel from the float bowl and spray itinto the air stream,

1200rpm as it is at 6000, it’s easy to get good mixture from a carburetor. But anything that changes or upsets this consistent signal makes carburetion more difficult.

thereby forming an air-fuel mixture. This low pressure—referred to as the “metering signal”—is the analog of the engine’s fuel needs.

The art in carburetion consists of ensuring that fuel is delivered in proper proportion, accomplished by means of fuel jets and airbleeds. As engine suc-tion draws air through the carburetor,the low pressure in the venturi, actingon the jets and airbleeds, delivers an approximately correct flow of fuel to the engine. And as rpm and throttle position change, correct fuel flow is approximately maintained.

We use the word “approximately” here because carburetors thrive on consistent intake signal. If the engine’s in-take process is much the same at

A bigger carburetor is the classic example. We put on a big carb to get more airflow to make more power on the top-end; but the bigger the carb, the slower the velocity of the air passing through it at any given rpm and throttle opening, and so the weaker its vacuum signal becomes. By giving the metering circuits weaker signals to work with, the big carburetor makes fuel delivery sluggish at lower rpm; the rule is, the bigger the carb, the bigger the tuning problems. But with electronic fuel injection, which does not depend upon intake vacuum signal, this problem simply goes away.

When an engine is modified—for example, by installing longer-duration cams and a less-restrictive exhaust system—the nature of the intake suction pulses is changed. Tuned

exhaust pipes may make intake suction stronger in certain speed ranges but weaker in others. And longer-duration cams weaken suction pulsing at lower rpm. Because the suction signal received by the carb has changed, so does the fuel mixture, thus the engine runs poorly.

Carburetion experts develop a feel for these kinds of situations. With a few running tests, a carb wizard can determine which way to go with changes to which systems. So, after installing different jets or other metering hardware, he has the engine again running nicely—although there still may be very little he can do to fully compensate for the weaker intake signal.

On a modified fuel-injected engine, however, none of this wizardry is useful. Injection systems operate on an entirely different set of principles that allow the delivery of fuel into the intake stream to be based on an engine’s actual

correct fuel quantity for the nozzle to inject at every engine rpm and throttle position. This information is determined through extensive dyno testing at the factory during the engine’s development stages. Fuel delivery is varied at many rpm points and throttle positions to find the on-time that gives maximum torque.The complete list of those variables, which relate max-torque on-time to rpm and throttle position, is what is called the “fuel map.” The map for street-legal motorcycles must also be configured to let the engine meet the prevailing emissions requirements; but on most modified or racing engines, the only criterion is maximum torque at all throttle settings and rpm points.

Because of the way in which fuel injection works, its accuracy does not depend upon the tricky correspondence between the engine’s actual fuel needs and the intake suction signal. EFI gives the engine what it needs because it

needs rather than simply on the flow of air over an orifice. By comparison, what fuel injection does makes what carburetors do seem like little more than guesswork. Here are the key basics of EFI:

Carburetors spray fuel continuously at arate that varies with airflow. Fuel injec-tion uses one electromagnetically con-trolled nozzle per cylinder to spray fuelin timed squirts—one spray per cylinderfor every two revolutions of the crank.The fuel pressure available at the nozzleis always constant, maintained at a regu-lated value in a fuel manifold by an elec-tric pump. Therefore, fuel quantity—and thus, the air-fuel mixture—is determinedonly by how long the nozzle is held open.That duration, called the “on-time,” is decided by a control computer.

The control computer—usually called an Engine Control Module (or “ECM”for short)—contains a kind of library in which is encoded the

knows what those needs are in all conditions by referring to the fuel map. Of course, if those fuel needs are changed because of modifications to the engine, the fuel map must be changed to suit.

The control computer knows the engine rpm and the throttle opening at all times because it receives signals from a tachometer and a throttle-position sensor. Before each fuel-injection spray is delivered, the computer effectively looks up the correct on-time for the current rpm and throttle position, then holds the nozzle open for that prescribed amount of time.

This is easy work for the computer because a typical ECM operates atbetween 1 and 10 million information processing steps per second—or 1 to10 Megahertz (MHz), to use popular computer terminology. This means that at, say, 5000 engine rpm, a 10 MHz computer can perform 120,000 such steps during each rotation of the crank-shaft, or 333 steps for every degree of crank rotation. The computer can operate this quickly because it is of

fingernail size, so electrical signals within it travel only tiny distances. This nearly instant response of EFI to changing conditions makes the engine much less likely to bog or hesitate when the throttle is opened suddenly.

Because fuel evaporates incompletely in a cold engine, carburetors use either a choke or an

What’s more, fuel injection is obedient. We’ve all experienced carburetion “flat-spots,” which typically occur on modified engines. A carburetor needs a venturi vacuum signal strong enough to make it spray fuel, but some combinations of exhaust pipes and cams, at certain speeds, can kill or even reverse that signal, causing a flat spot that often is impossible to eliminate. Fuel injection, however, is immune to such problems; it merely does what it is told by the fuel map and sensors.

enrichening system to richen the mixture for cold-starting. Carburetors run richer as the weather warms and leaner as it grows colder, thereby changing the power available. And carburetors also allow the mixture to be too rich as we ride to the top of Pike’s Peak, where the air is thinner, and too lean as we travel into Death Valley, where the air is more dense.

Racers get peak performance in all conditions by changing carburetor jetting to maintain a best-power mixture—not a viable technique for general street riding. In production streetbike engines, carburetion is set rich enough to safely cover anticipated running conditions while also meeting requisite emissions standards, and we tolerate any power losses these trade-offs might produce.

With the processing power of a computer, however, these compromises disappear, and all this tuning work can be done automatically. Sensors located around the motorcycle report engine temperature, atmospheric pressure and air temperature to the computer, which then uses simple arithmetic (you can do a lot of figuring in 120,000 steps) to modify the engine’s fuel delivery according to all these variables. This is why fuel-injected engines start so well when cold, why they can be immediately ridden off without stalling or hesitation, and why they don’t blubber with excess fuel at very high altitudes or starve for fuel at very low altitudes. The fuel map provides the basic data for fuel delivery, and the sensors modify this information according to current engine temperature and air density.

There are things you just can’t do with carburetors, such as vary the time at which fuel reaches a given cylinder, or change the mixture only in one particular part of the rpm band, or vary the strength of the mixture from one

Okay, you’re thinking, this is wonderful stuff if you happen to be a computer hacker or an engine developer working for a motorcycle manufacturer. But what about the rest of us? How do riders who want to modify their fuel-injected engines manage to get their fuel mixtures correctly adjusted?

Well, more easily than you might think. Every day of the year, thousands of people who aren’t computer geeks or software programmers tune fuel-injection systems. No programming is necessary. All we need is a way to tell the computer what we want. Several such ways exist.

In some ECMs, the fuel map is stored on a replaceable computer chip. Engines modified with certain cams, pipes and other parts have already been tested and mapped by some OEM or after-market manufacturers, and chips with such maps are available for users running those specific combinations. This is a plug-in replacement.

Some injection systems can be adjusted either by a special hand-held recalibration unit or by a laptop computer. The existing fuel curve—which relates mixture strength to rpm—can be downloaded and displayed on the computer’s screen. Then you can enrich or lean out the whole curve, or any section of it, by any amount. Once you’ve made the changes you want, you upload the new fuel curve back into your ECM.

The net effect is analogous to that of changing jets, but it can be much more specific. Plus, you remove no parts from your bike. No jets will roll into inaccessible places, and there won’t be a sticky place in your driveway from draining a

cylinder to another, or even from one gear to another. With fuel injection, all of these options—and many more—are not only possible but easy to accomplish.

carburetor float bowl. Mechanics at racetracks do this job every day: plug in, download, adjust, upload, road test.

For some time, companies have marketed devices for fuel-injection tuning. These devices change fuel delivery either by supplying adjusted sensor data to the ECM, or by directly changing the on-time of the pulses the ECM sends to the injector nozzles.

Now companies have even begun to offer a service, at some of their associated dynocenters, by which the fuel injection on a motorcycle with any combination of modifications can be reprogrammed quickly and automatically. While running on the dyno, and with an oxygen sensor in the exhaust to measure fuel mixture in real time, the engine is accelerated under the control of the company's tuning software, operating through the bikes ECM. As the dyno run progresses, all the many data points are automatically gathered and stored. Essentially, this system “learns” the correct fuel mixture curve as it runs, and this data is automatically stored in the system on the bike as its new fuel map.

Time consumed? Such a dyno run takes typically 20-40 seconds. No muss, no fuss, no trial-and-error involving the repeated threading of jets into and out of a hard-to-reach float bowl located on the bottom of a carburetor inconveniently tucked behind an air cleaner. An engine tuned in this fashion—whether nearly stock or highly modified—will start easier, run smoother, respond more quickly, accelerate harder.

So, electronic fuel injection is nothing to fear; it’s merely a newer, better way to fuel an engine. And don’t think of injection as the stealthy hand of Big Brother, either, because convenient tools are available by which to control it. Yes, EFI exists in the first place because it does the best, most flexible, most accurate job of controlling engine exhaust emissions, but it is also a superior high-performance fuel system in its own right.

This is why you should learn to work with fuel injection. Its principles are not that difficult to grasp; and once you do, you’ll soon find that you have more and better control over engine performance than you ever had with carburetors. Whether you like it or not.

The Fall of the Carburetor

For most of the existence of the internal combustion engine, the carburetor has been the device that supplied fuel to the engine. On many other machines, such as lawnmowers and chainsaws, it still is. But as the automobile evolved, the carburetor got more and more complicated trying to handle all of the operating requirements. For instance, to handle some of these tasks, carburetors had five different circuits:

Main circuit - Provides just enough fuel for fuel-efficient cruising Idle circuit - Provides just enough fuel to keep the engine idling

Accelerator pump - Provides an extra burst of fuel when the accelerator pedal is first depressed, reducing hesitation before the engine speeds up

Power enrichment circuit - Provides extra fuel when the car is going up a hill or towing a trailer

Choke - Provides extra fuel when the engine is cold so that it will start

In order to meet stricter emissions requirements, catalytic converters were introduced. Very careful control of the air-to-fuel ratio was required for the catalytic converter to be effective. Oxygen sensors monitor the amount of oxygen in the exhaust, and the engine control unit (ECU) uses this information to adjust the air-to-fuel ratio in real-time. This is called closed loop control -- it was not feasible to achieve this control with carburetors. There was a brief period of electrically controlled carburetors before fuel injection systems took over, but these electrical carbs were even more complicated than the purely mechanical ones.

At first, carburetors were replaced with throttle body fuel injection systems (also known as single point or central fuel injection systems) that incorporated electrically controlled fuel-injector valves into the throttle body. These were almost a bolt-in replacement for the carburetor, so the automakers didn't have to make any drastic changes to their engine designs.

Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection (also known as port, multi-point or sequential fuel injection). These systems have a fuel injector for each cylinder, usually located so that they spray right at the intake valve. These systems provide more accurate fuel metering and quicker response.

When You Step on the Gas

The gas pedal in your car is connected to the throttle valve -- this is the valve that regulates how much air enters the engine. So the gas pedal is really the air pedal.

A partially open throttle valve

When you step on the gas pedal, the throttle valve opens up more, letting in more air. The engine control unit (ECU, the computer that controls all of the electronic components on your engine) "sees" the throttle valve open and increases the fuel rate in anticipation of more air entering the engine. It is important to increase the fuel rate as soon as the throttle valve opens; otherwise, when the gas pedal is first pressed, there may be a hesitation as some air reaches the cylinders without enough fuel in it.

Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust. The ECU uses this information to fine-tune the fuel delivery so that the air-to-fuel ratio is just right.

The Injector

A fuel injector is nothing but an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump in your car, and it is capable of opening and closing many times per second.

Inside a fuel injector

When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel -- to make as fine a mist as possible so that it can burn easily.

A fuel injector firing

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.

Fuel injectors mounted in the intake manifold of the engine

The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.

In this picture, you can see three of the injectors. The fuel rail is the pipe on the left.

In order to provide the right amount of fuel, the engine control unit is equipped with a whole lot of sensors. Let's take a look at some of them.

Engine Sensors

In order to provide the correct amount of fuel for every operating condition, the engine control unit (ECU) has to monitor a huge number of input sensors. Here are just a few:

Mass airflow sensor - Tells the ECU the mass of air entering the engine Oxygen sensor(s) - Monitors the amount of oxygen in the exhaust so the ECU can determine

how rich or lean the fuel mixture is and make adjustments accordingly

Throttle position sensor - Monitors the throttle valve position (which determines how much air goes into the engine) so the ECU can respond quickly to changes, increasing or decreasing the fuel rate as necessary

Coolant temperature sensor - Allows the ECU to determine when the engine has reached its proper operating temperature

Voltage sensor - Monitors the system voltage in the car so the ECU can raise the idle speed if voltage is dropping (which would indicate a high electrical load)

Manifold absolute pressure sensor - Monitors the pressure of the air in the intake manifold

The amount of air being drawn into the engine is a good indication of how much power it is producing; and the more air that goes into the engine, the lower the manifold pressure, so this reading is used to gauge how much power is being produced.

Engine speed sensor - Monitors engine speed, which is one of the factors used to calculate the pulse width

There are two main types of control for multi-port systems: The fuel injectors can all open at the same time, or each one can open just before the intake valve for its cylinder opens (this is called sequential multi-port fuel injection).

The advantage of sequential fuel injection is that if the driver makes a sudden change, the system can respond more quickly because from the time the change is made, it only has to wait only until the next intake valve opens, instead of for the next complete revolution of the engine.