Carburetors and fuel injectors are ubiquitous terms in motorsport, with the former being used in almost all vehicles up until the 1980s. Fuel injection has been adopted by all car manufacturers now, but they can still be found on older vehicles, and even in some NASCAR vehicles.
Fuel injection is by far the most effective and efficient method of fuel delivery, but that doesn’t mean carburetors don’t have their own advantages. Although fuel injection provides more accurate air to fuel ratios, they are far more expensive than carburetors, and harder to fix.
But there is more at stake than just prices of repairs and fuel economy. Carburetors and fuel injection systems have their own lists of advantages and disadvantages, and so we need to look at each one in more detail to find out which one really does come out on top.
A Brief Overview Of A Carburetor
The Old Way
Carburetors are mechanical components found in most older cars, and some modern race cars and small motorcycles. They were the most popular method of fuel delivery for combustion engines until the 1980s and are often simply referred to as carbs. They are made of metal and are found connected to the engine and a fuel reservoir, which is separate from the fuel tank itself.
The mechanism of a carb looks quite complex, but it is essentially a system of valves and tubes that take advantage of a physical phenomenon called the venturi effect. Essentially, there is a narrowing of the tube inside the carburetor that causes air to speed up as it passes through it. As the gas pedal is pressed, more air is allowed to pass through the carb, which speeds up even more.
Air Pressure Differences
As the air speeds up, it decreases the pressure inside the carburetor, which is connected to a fuel reservoir. The pressure at the top of this reservoir is that of the atmosphere, which is higher than that of the carburetor. This pressure difference causes the fuel to be pushed into the carburetor, and then into the engine, where it is burned as the car accelerates.
When the gas pedal is released, the air flow is reduced, which means the pressure inside the carb increases, and in turn the amount of fuel going into the engine decreases. This is a very simple explanation, but essentially the carburetor works using air pressure to send more fuel into the engine when the car needs more power under acceleration.
Electronic Fuel Injection
There are a few different types of fuel injection, with both mechanical and electronic options. However, for the sake of this article we will be referring to electronic fuel injection (EFI). EFI is an alternative method of delivering fuel into the engine, and it works using a system of electronic pumps connected to the fuel tank.
The pumps are used to send fuel towards the engine through fuel lines, which then spray fuel into the engine at various points depending on the type of system used. They do this electronically, with several sensors being used to determine the amount of fuel to be delivered to the engine at any time.
Advantages Of Carburetors
Cheap To Build & Maintain
Carburetors present one clear advantage and that is their low price. They are made from relatively few components and could be cheaply mass produced for vehicles all of the world. Their lack of electronic components means they are reliant purely on air pressure differences, which makes then fairly simple to build and maintain.
This presents another key advantage, in that they can not only be acquired easily and cheaply, but they can also be easily fixed. You only need to have some basic mechanicalknowledge and a few tools to be able to fix a carburetor, but even if you don’t feel up to the challenge you can take it to your local garage and it might only cost you afew hundred dollars.
They are separate from the engine too, which makes things much easier as dealing with the engine and having to take it apart to reach the carburetor would be excessively difficult. They can be tuned too, which means they can be made to suit different environments, elevations and even driving styles.
Disadvantages Of Carburetors
With these key advantages come several big disadvantages. Carburetors are cheap and easy to repair, but the fact that they work purely mechanically means they are affected by several different factors that other systems are not. The main one is air pressure, as the amount of fuel being sent into the engine depends on the pressure difference in the fuel reservoir.
Higher altitudes, such as if you live in the mountains, would mean your carburetor would deliver a different amount of fuel to the engine than if you lived at sea level. Although this can be tuned out, carburetors cannot adapt on the fly and so may need a lot of tuning over time. This fluctuation in air-fuel mixtures means the engine cannot always perform optimally.
Not Very Efficient
The systems are also just not veryefficient and are quite an old technology now. They often offer a bit of throttle lag too, which means there is a delayed throttle response. This is of particular interest to those with racing cars, as they need their throttle response to be as fast as possible for tight racing situations.
Advantages Of Fuel Injection
Control Over The Air-Fuel Mixture
Fuel injection works electronically, and not mechanically. This means the air-fuel mixture that is sent to the engine is not just dependent on the differences in pressure, but it can be controlled very precisely with various electronic sensors. This provides a much more efficient system, with air to fuel ratios being controlled at the granular level.
The air to fuel ratio will drastically affect the car’s performance and fuel economy, and so being able to control it, often completely automatically, makes EFI very useful in all kinds of vehicles, especially in racing. This can also allow for more complete combustion, which essentially means the fuel can be burned in a cleaner way, giving out less pollutants.
Various Options Available
There are a few different types of EFI systems available, with direct, port and indirect options. These come with their own benefits, but as the fuel is being sprayed directly into the engine with the first option, more consistent fuel delivery is offered, leading to more efficient engines. Port and indirect offer their own advantages too, and the electronic spraying of fuel also provides a cleaning effect.
The better fuel efficiency is a big bonus too, but EFI can also offer slightly more power over carbureted systems, along with a faster throttle response. Finally, fuel injection systems are usually very reliable, and require little to no maintenance. They also rarely break down, and fuel injection systems can last the car’s entire lifetime without needing replaced.
Disadvantages Of Fuel Injection
Expensive To Repair & Replace
The first main disadvantage of fuel injection is when they do break down, they are expensive. The electronic components used within them mean that they cannot just be fixed on the side of the road like a carburetor can, as specialist parts are often required. This drives the time to fix them up, along with the price, with replacements often costing thousands of dollars.
Although the EFI system of your car will be tuned to suit the car, and it won’t be affected by as many environmental factors as carburetors, there is still not a huge amount of room for adjustment. The electronic control unit (ECU) of the car can be mapped in different ways, but they are often difficult to customize without some expensive work.
So, Which Is Best?
EFI Is The Best
Electronic fuel injection is definitely the most common option in the modern world, with no motoring companies opting to produce new cars with carburetors. However, you will still often find carbs on older cars, and on some smaller motorcycles as they help to keep the costs down. Plus, NASCAR Xfinity and Truck races still allow for carburetor-fed engines to be used.
But EFI is just the more efficient option. With higher costs they may put a hole in your wallet if they need repaired, but they are designed to last a long time. Higher repair costs are outweighed by the better fuel economy and faster throttle response. And with more consistent and complete combustion of the fuel in the engine, they are a cleaner option for the environment too.
There are advantages and disadvantages to both carburetors and fuel injection systems. Where carburetors are cheaper and easier to fix, fuel injection systems are more efficient and offer more consistent combustion. Although they are more expensive, their high reliability and fuel economy makes them the most common fuel delivery system in use today.