Motorcycling - Knowledge

Carburetor Vs Fuel Injection: Which One to Pick for your Motorcycle

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Not all bikers are aware of the functionality of the carburetor or the fuel injection system on their bike. Many don’t have any interest in it at all. But, why should you know about it? It is because this little thing on your bike has the capability to change your whole riding experience. But, when talking about Carburetor vs. fuel injection, which one of the two delivers a better performance? This question is highly debated since a long time. 

Some believe that carburetor is the best option while some others believe that that the fuel injection in bikes is the way to go and it is for good reason that they are taking over carburetors. To be able to decide the best vehicle for yourself, you would first need to understand the functionality of both the components. So, let’s get started. 

Table of Content

  • Carburetor vs. Fuel Injection- Engine Performance 
  • Historical Perspective: Carburetor vs. Fuel Injection 
  • Know All About Carburetors in Bikes
  • What Happens When The Vehicle Has Been Running For Several Years
  • Know All About Fuel Injection System in Bikes
  • Carburetor vs. Fuel Injection: Pros and Cons
  • Carburetor vs. Fuel Injection- Which One Is Better

Carburetor vs. Fuel Injection- Engine Performance 

The performance of both the carburetor and the fuel injection system is dependent on the amount of gasoline and air that can enter the cylinder. These cylinders contain the combustion chambers and the pistons wherein the energy gets released due to the combustion if the gasoline. The fuel injection system and the carburetor, both would feed air and fuel to the engine. 

carburetor vs fuel injection
Which is the best performer? (source)

Historical Perspective: Carburetor vs. Fuel Injection 

Talking about Carburetor vs. fuel injection, the carburetors of the early times relied on the flow of air over the liquid fuel. Only the fuel vapours were collected for the purpose of ignition. With advancement in technology, the later versions began to make use of the principle of Bernoulli so as to improve the amount of fuel reaching the cylinders. It was basically the amount of air flowing in through the venture which would deliver the fuel in exact proportion as that of the air entering the intake. 

Soon, vehicles with carburetors began to fade away and towards the early 1990’s; fuel injection became quite popular and had taken over carburetors. Fuel injection systems date back to the time when the first engines were developed.

But, if they existed at that time, why weren't they so popular?

It is because of the fact that the complexity involved with these systems prevented its usage until the 1920’s. 

It was only later from the mid-1950 that the fuel injection systems became quite popular and started being used in both gasoline and diesel engines (in both the electronic and mechanical versions).  The carburetor was replaced by the electronic fuel injection systems that used a throttle-body injector. 

With the Port fuel injection, individual fuel injectors were placed quite close to each of the intake valve. This helps in powering most of the modern automobiles. Quite similar to the diesel engines, a few gasoline engines were also fitted with the direct fuel injection. 

Know All About Carburetors

The bike carburetor is one of the essential mechanical parts of a bike and several small engine machines. All kinds of engines, no matter what size, need an appropriate mixture of fuel and air for the purpose of combustion. It is the carburetor that is responsible for controlling the ratio of air and fuel mixture that enters the engine. Okay, so this sounds pretty simple, right? Of course, it is but for an efficient output, all of the components present inside it has to function properly. There are several parts which if not set properly would prevent the vehicle from running. 

Therefore, the ideal air and fuel ratio is essential for the engine to perform correctly. 

Types of Carburetor 

Different types of carburetors are used so as to match the fuel flow to the requirements of the engine. The carburetors are:

  • Up-drought or vertical
  • Down-drought or Inverted
  • Horizontal Drought 

In a vertical or up-drought carburetor, the mixture of air/fuel flows in an upward direction. The arrangement is quite convenient for the gravity flow of the fuel with a rather low overall height. 

The inverted or down-drought carburetor allows the flow of the mixture of air/fuel in a downward direction. This kind of carburetor is the most preferred one as it is the most accessible one and one can easily attach the air-filter. Also, there is a much lesser chance of settling out of the fuel’s heavier fractions as the particles of liquid flow in the gravity’s direction. 

The horizontal carburetor can provide higher charge efficiency because of its shorter connection to the intake manifold. However, this kind of carburetor isn't favoured for the installation of an air filter.

Carburetor types are most commonly classified on the basis of barrels that are used. It could either be one-barrel, single-stage two-barrel, two-stage two-barrel and four-barrel. 

How Does the Carburetor Work? 

When comparing between Carburetors vs. fuel injection, engines with carburetors are said to produce more amount of raw horsepower as compared to the fuel injection engine.  Also, the functioning of the carburetors is rather simple which makes it rather easy to configure, adjust, rebuild or troubleshoot. The carburetor supply fuel to the engine with the help of a  phenomenon that is referred to as Vacuum Venturi Effect.  

The air gets into the carburetor through the air filter and then gradually speeds up. This happens because of the carburetor’s narrow interior walls. This air blows in a perpendicular direction to the valve that is controlled by the cable of the throttle. The throttle slide present inside the main body of the carburetor rises because of the cable which happens when the throttle is pulled open. 

As soon as this slide rises, the strong air that was entering would fuel up the main jet. Now, this happens automatically because of the fact that the fuel wants to travel to an area of low pressure (It is basically the main body of the carburetor) from an area of high pressure (the float chamber). 

Here the air and the fuel mix up and then travel towards the engine. The amount of fuel that would flow would completely be dependent on the size and the position of the needle valve, fuel’s height in the float chamber and the main jet’s size. The height of the fuel in the float chamber would be controlled by the floats. The floats in the carburetor of the bike would need to be adjusted properly for it to function efficiently. If you are looking for how to tune bike carburetor for mileage, then you can try- warm up the engine, increase the air intake, tune the idle screw and much more. 

working of a bike carburetor
How does bike carburetor works?

Components of the Float Chamber

The float chamber is basically a reservoir for the fuel and also contains the float’s working components. In most cases, the float chambers have a drain that aids in maintenance. In a few cases, it might also be used to measure the height of the fuel. Make sure the float height is accurate else mishaps can happen. 

Also, as the carburetor is an open system, it allows some amount of fuel to evaporate. When the bike is running, the air intake isn’t sealed and the fuel present in the carb slowly evaporates.  However, the amount of fuel lost is rather less as compared to the whole lifetime of the vehicle. During the cold season, getting the engine started can pose as an issue. 

What Happens When The Vehicle Has Been Running For Several Years? 

As the vehicle begins to get old, it may develop a few vacuum air leaks from the various vacuum lines that are used in the engine compartment. Due to the leaks, additional air might be drawn to the intake manifold. This would change the mixture of air and fuel from the ideal blend to a leaner blend which is basically too much of air and not enough amount of fuel. 

In case any amount of additional air is added to the intake system with the similar amount of fuel as had been done before, it would lead to a rather high temperature of the combustion chamber. The functioning of the carburetor is dependent on the air’s velocity that enters the venture so as to create an ideal air and fuel mixture to feed to the engine. This would serve to maintain fuel circuits that pump the petrol. If you compare Carburetor vs. fuel injection, you would find that most of the high-performance bikes these days have adopted fuel injection. However, there are still many that have carburetor engines fitted in them. 

Know All About Fuel Injection System in Bikes

Do you know what’s the good thing about a fuel injection system?

It’s the fact that you can simply turn your key in the ignition, get on your bike and then speed off without having to think too much. All of this might seem too easy for words but the mechanics are far more difficult. It is for this reason that it wasn’t used in the early times. 

Now, there’s a fuel pump present inside the tank along with an electronic controller of the engine and an array of sensors. The fuel that is injected into the system is usually controlled by the fuel delivery system. The ECU takes the information from several sensors and also helps in determining as to how much fuel the engine would receive based on the gathered data. All the other sensors deal with the temperature of the engine, RPM, crankshaft position and the position of the throttle. 

The fuel necessary for the load condition and RPM is situated within the ECU in the fuel map. The ECU would adjust the mixture of the fuel for engine and air intake temperature as soon as the identification of the amount of fuel is done. The electronic fuel injection systems would consist if an oxygen sensor, a computer, a fuel pressure regulator, fuel injectors along with an electric pump for fuel. As soon as the key is turned on, the ECU would run a check so as to ensure that everything is fine and is ready to go. 

fuel injection for bikes
Fuel Injection for a smooth ride (source)

Types of Fuel Injection System

The different types of fuel injection system which are extensively employed in the modern age vehicles for improved performance and enhanced fuel economy have been discussed below:

1. Single Point Injection or Throttle Body (TBI)

This is undoubtedly the simplest fuel injection system that was used in cars in place of the carburetors. This system employs one or two fuel injectors which are placed in the throttle body and can deliver an appropriate ratio of air/fuel mixture to each and every fuel intake manifold in the vehicle’s engine. 
 
The only drawback of the system is that the cylinders present very close to the fuel injectors would get the ideal mixture as compared to the ones that are away from it. However, the reason why single point injection was able to replace the carburetors was due to the fact that, it has the capability to adjust easily according to the altitude and air-density and remained independent of the vacuum manifold. 

Single Point Injection System
Simple yet reliable (source)

2. Direct Injection (DI)

The direct injection is undoubtedly one of the most advanced fuel injection systems. These can most commonly be found on the diesel engines. But, slowly this technology is making its way to the petrol engines. In this system, the fuel is directly injected into the combustion chamber which is basically the cylinder.
 
The biggest advantage of this system is that there is absolutely no wastage of carbon deposit or fuel at the intake valve. The sensors keep a check on the exact amount of fuel that would be required by the vehicle and then supply the same to the chamber. The fuel metering of this system is more accurate than any of the other systems. 

types of fuel injection system
Direct Injection System- No wastage of carbon deposit (source)

3. Multi-Point Fuel Injection or Port Injection (MPFI) 

Just as the name suggests, the port injection or the Multi-point fuel injection means just one fuel injector for each of the cylinders situated at the intake port of the manifold. So, if the engine has about let’s say six cylinders then it would have six fuel injectors. As the fuel is situated so close to the intake manifold, it would ensure that the whole of it is used for combustion. 
 
This, therefore, makes it more efficient than the TBI and therefore facilitates in an improved fuel economy as well. The multi-port fuel injectors fire the fuel all at same time wherein the fuel remains at the manifold till the time comes. With this kind of system, even fuel distribution is possible. 

Port Injection
Even fuel distribution (source)
  • Sequential fuel injection (SFI)

The Sequential fuel injection system is basically a type of MPFI. As discussed above, in a MPFI, all of the injectors are fired at the same time while in an SFI they are fired depending on the cylinder’s intake timing. This means that it happens just before the cylinder’s intake valve opens. Thus timing is matched with the camshaft and it might seem like a very small change but it sure has helped with the emissions and efficiency.  

How Does the Electronic Fuel Injection System Work? 

The fuel injection system for the bike works exactly similar to the ones present in trucks, cars and all the advanced engines. The engines with fuel injection are electronically controlled by the ECU (Engine Control Unit), a tiny computer present within the engine which measures a lot of variables like the temperature of engine and air, RPM’s, throttle and crankshaft position. All these help in determining the amount of fuel that would enter the engine through fuel injectors. This would hence create much fewer emissions and so less energy would be created. This means a more responsive acceleration and a smooth ride for the rider. 

All of the modern and advanced fuel injectors in the bikes are capable of opening and closing several times in a second. In the above discussion of Carburetor vs. fuel injection, we did say that that the EFI might seem complex but it is just its components that would make it appear so. If you actually look into it, you would realize that the EFI is a lot simpler than the carburetors.

Electronic Fuel Injection System
Efficient Working (source)

Carburetor vs. Fuel Injection: Pros and Cons

Listed below is a brief discussion on the pros and cons of Carburetor vs. fuel injection. By going through it, you would be able to understand as to which one is better.

Performance and Power

With advancement in technology, the modern electronic controls, and the fuel injections have become more accurate and therefore the fuel delivery can easily be tuned to match the demand of the driver. The carburetors too were, of course, efficient and precise but they weren't as accurate as fuel injection. They couldn’t account for the changes in the temperature of fuel or air or the atmospheric pressure. 

Fewer Emissions and Reduced Fuel Consumption

Which to pick- fuel injection vs carburetor? This will help you to pick the right one. As the fuel injection can be controlled precisely would result in a much more efficient usage of the fuel. This means fewer emissions and even lesser consumption of the fuel.  This is perhaps the biggest reasons as to why it had started to replace carburetors. 

Complexity and Affordability

This is perhaps the biggest difference between carburetor and fuel injection. If we talk about complexity and cost, carburetors are definitely the winner here. They are simple, inexpensive and most importantly, reliable.  It is perhaps the reason why still many people choose carburetors over the fuel injection systems. All you would need is a couple of hand tools, a carburetor cleaner, and a few spare parts and you would easily be able to rebuild a carburetor. However, when it comes to fuel injection systems, even with a few years of expertise and advanced gears, you might not be able to identify the issue and fix it all by yourself. It is for this reason that most of the small engines are still equipped with carburetors. 

Carburetor vs. Fuel Injection- Which One Is Better? 

Before we tell you what we feel is better, after going through the above discussion of Carburetor vs. fuel injection, which one according to you is the better one? Most people would definitely say the fuel injection system because of the efficient performance and power. Also, it does seem quite obvious that in a few years of times, most of the automobiles would be opting for the fuel injection system because of the lower emission. But, unless and until the costs of these systems reduce, there would still be a lot of people who would like to stick to the carburetors. 

carburetor vs fuel injection engine
Final Verdict- which is the best? (source)

If you take a look at the pure horsepower, you would see that the fuel injection power only has the capability to deliver approximately 10 extra horsepower when is at its peak. The fact that it can constantly tune air and fuel intake for each of the cylinders is what benefits its performance. Therefore, in our opinion, the fuel injection systems are the best as they would not only reduce the vibrations but would also offer assistance in overcoming the steep grades which are the traditional terrain when it comes to off-roading. 

Which one out of the two would be best for you would be completely dependent on your need and the kind of performance you would want your vehicle to deliver. Think about it wisely and then make your decision. 
So, after going through the whole article, what is your opinion? Do you feel that the fuel injection system taking over the carburetors is a good change? Feel free to share your views in the comment section below. 

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Team Livingit
Motorcycling - Enthusiast
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