Fuel Injection Vs. Carburetion – Which Is Better?

Once upon a time, back in the 80s, hardcore car enthusiasts argued whether fuel injection is better or not in much the same way some argue today whether electric cars are better. But today, thirty years later, it’s clear that fuel injection was the winner compared to carburetion, and for good reasons.

The fuel injection vs. carburetion differences are pretty simple. Fuel injection is computer-controlled, which equals much more control over fuel delivery. That results in more power and better fuel consumption, among other things. Carburetors are entirely mechanical with fixed fuel delivery parameters, and their only advantage is a lower cost of manufacturing.

Fuel Injection

Before we dive into fuel injection vs. carburetion, a brief history lesson. Although fuel injection has been around in various forms since the 1900s and through the 1940s, pretty much all fuel-injected vehicles during that period had diesel engines. The only exception to that is the Swedish Hesselman gasoline engine made for buses and trucks, but then again, that engine could run on several types of fuels, including diesel, so it hardly qualifies.

The first gasoline-powered fuel-injected passenger car was the 1954 Mercedes-Benz 300SL, which, like all the fuel-injected cars in the following decades, had mechanical fuel injection. Those mechanical fuel injection systems were extremely expensive to produce and were far from reliable. That’s why a lot of classic car owners convert mechanical injection to carburetors, and needless to say, that type of injection was never going to be a substitute for carburetors.

Then, enter the 1980s, the rise of computer software, microchips, and high-end electronics. That’s when fuel injection evolved into the system we all know today. And that’s a computer (ECU) controlled fuel injection with one fuel injector for each cylinder, also called port injection or MPI.

The reason computers are so important for fuel injection is that they can take into account the air pressure, air temperature, airflow, and the amount of oxygen in the exhaust to precisely determine how much fuel an engine needs at any given moment. That allows for an optimized fuel delivery regardless of outside conditions or engine load.

Also, in a fuel injection system, the fuel is under constant pressure as it enters the combustion chamber through almost microscopic holes in the fuel injectors. That atomizes the fuel immeasurably better than carburetors, which, again, results in more efficient combustion. Also, the whole system, apart from computer programming, is pretty straightforward.

There is a fuel pump in the tank that moves fuel to the engine, where it enters a fuel rail. The rail has a pressure regulator that sends excess fuel back to the tank, but before that, all injectors are plugged into the rail. Those injectors are electronically controlled, and the ECU can open them for any duration of time it deems best, giving it all the control it needs.

There are also the more modern direct fuel injection systems where the fuel injectors don’t spray fuel into the intake manifold but directly into the combustion chamber. The whole system is very similar to port injection, with the only exception being a secondary, high-pressure fuel pump.

The high-pressure fuel pump sits on the fuel rail and pressurizes the fuel before they go into the injectors to as much as 2,000 psi. That complicates the system somewhat and increases maintenance costs and the initial production cost, but it further optimizes fuel efficiency, which gives you more of all the advantages a conventional fuel injection system provides. That means even in those highly complicated systems, the disadvantages of fuel injection over carburetor are almost invisible.

 

Advantages of Fuel Injection

Disadvantages of Fuel Injection

Carburetion

Carburetors with varying designs but the same working principles have been around for as long as passenger cars have. And we mean that literally because the first carburetor was invented by Karl Benz in 1888, two years after he made the first ever passenger car, the Benz Patent Motor Car.

Given how simple the design is, with nothing more than a molded piece of aluminum and a couple of jets, carburetors stuck around until the late 1980s and even late 1990s in some cars. The reason why is pretty simple, nothing beats the carburetor when it comes to low production costs.

Now, here is how the carburetor works. Under the carburetor is a small fuel tank, also called the float bowl. Between the float bowl and the throttle body passage is a main jet that’s essentially just an appropriately sized hole. Then, as the engine is running and making a vacuum, it sucks fuel through the main jet and into the intake airflow. After that, the air, now mixed with fuel, enters the combustion chamber, and job done.

But as we mentioned earlier, the problem with carburetors is control over fuel delivery. A carburetor has a main jet that works at wide open throttle, and then a pilot jet that works at idle, and a needle jet that works between idle and full throttle. The problem is that these jets are nothing more than bolts with holes, and the size of those holes (jets) is what determines the amount of fuel entering the engine.

And while that system works well in optimal outside conditions, things quickly change when the air temperature is high or low or when you are at higher altitudes. For example, at lower temperatures, the air contains more oxygen, so the engine needs more fuel. But since the jet sizes are fixed, they can’t account for weather changes resulting in a subpar air/fuel ratio. The same goes for high air temperatures and extreme altitude changes.

And, of course, the fuel atomization isn’t that good either because the air flowing through the carburetor is the only thing atomizing the fuel. And while that works well enough for the fuel to burn, it’s far from optimal.

Then, there are forced induction engines where all those outside condition changes have a substantially greater effect on the air/fuel ratio. Not to mention that tuning a carburetor for boost is extremely difficult, even in optimal laboratory conditions. And that’s another big reason why carburetors are no longer around.

Advantages of Carburetion

Disadvantages of Carburetion

Fuel Injection Vs. Carburetion Differences

When it comes to fuel injection vs. carburetor differences, the main one is control over fuel delivery. A carburetor has a fixed and preset “fuel map” or carburetor jet sizes, while a fuel injection system can correct the fuel flow thousands of times per second.

Of course, the components of both systems are largely different as well. The only shared component between the two systems is the in-tank fuel pump, but even that isn’t always the case. A fuel injection system has multiple injectors, a fuel rail, a wiring harness, an ECU, a fuel pressure regulator, and a separate throttle body.

On the other hand, a carburated engine has the carburetor itself, and that’s pretty much it. All other components, including the throttle body and jets, are integrated into the carburetor. And with that, it’s clear just how a carburetor system is simple and consequently cheap.

Still, the fuel injection, especially today, more than makes up for the extra cost with better fuel economy, almost no regular maintenance, and much better reliability. Not to mention that a fuel injection system is better for the environment.

FAQs

Which is better, fuel injection or carburetor?

Fuel injection is far superior to a carburetor because it’s much more efficient, resulting in lower fuel consumption, more power, and lower CO2 emissions. Also, fuel injection is much more reliable and doesn’t require regular maintenance.

Does fuel injection make more power than a carburetor?

Yes, even in optimal conditions, fuel injection makes slightly more power than a carburetor. But in extremely hot or cold temperatures, under high engine loads and extreme altitudes, fuel injection makes noticeably more power than a carburetor.

Why are carburetors not used anymore?

Carburetors are not used anymore mainly because they increase fuel consumption and, more importantly, air pollution. Also, carburetors don’t go well with forced induction, and with the ever-rising popularity of turbocharged cars, they quickly became obsolete.

Is it worth changing the carburetor to fuel injection?

Whether or not it’s worth changing the carburetor to fuel injection depends on the car model. For example, changing an LS engine to fuel injection is definitely worth it because all the necessary parts are readily available and fairly cheap. However, converting an old BMW to fuel injection is extremely expensive, time-consuming, and difficult, making it not worth the hassle.

Do carburetors have any advantages over fuel injection?

Yes, carburetors do have some advantages over fuel injection, and those are a lower cost of manufacturing and DIY friendliness. However, fuel injection systems are extremely cheap nowadays, so the advantages of carburetors over fuel injection are neglectable.

Is it hard to switch from carburetor to fuel injection?

Yes, in most cases, it’s extremely difficult to switch from carburetor to fuel injection. To do that, you need a new intake manifold, throttle body, wiring, a standalone ECU, a new fuel pump, and a lot of knowledge to make it all work. However, on some engines like the Chevy small block series or the Ford Cleveland, it can be fairly easy.

Final Words

Ultimately, it’s all about control when it comes to fuel injection and carburetors. Fuel injection is electronically controlled and much more efficient because of as are all components that switch from mechanical to electronic.

Fuel injection makes more power, burns less fuel, makes less harmful exhaust gasses, is more reliable, etc. The only thing the carburetor has going for it is a low price, but even that is neglectable today.

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