Do NASCAR Engines Use Carburetors Or Fuel Injection?

If you are a car fanatic, or just have a general interest in all things automotive, you have probably heard the terms carburetor and fuel injection a lot. Carburetors were once the norm as a way of delivering fuel to the engine, but since the 1980s they have been replaced by fuel injection systems.

NASCAR used carburetors in their Cup Series cars up until the 2011 season, but they then switched to electronic fuel injection. Some cars in the Xfinity and Truck series still use carburetors as their method of fuel delivery, and it is unclear whether or not that will change any time soon.

There are many differences between the two types of fuel delivery, and we will explore each down below. Both have their advantages and disadvantages, but electronic fuel injection is the way of the modern vehicle and has been for some time, so we will consider how that affects NASCAR too.

What Is A Carburetor?

A Simple Component

A carburetor, or carb, is an important piece of mechanical engineering that has its origins in the 19th century. They were invented as a means to deliver fuel into combustions engines, and they remained in use in most vehicles until the 1980s. They can look quite complex, but they work via some very simple physical processes, with the outcome using air pressure to deliver fuel into the engine.

They are made up of a few key components, with the essentials being valves at the top and bottom, separated by a tube that narrows at the middle, before widening again. Just above this narrow part is another tube connected to a fuel reservoir, which is in turn connected to the fuel tank of the vehicle. The bottom of the carburetor is the exit to the engine, where the fuel is burned.

Basic Physics

The valve at the bottom of the carb is the throttle valve. This is closed until you press the gas pedal, which opens the valve and lets the air flow through the carburetor into the engine along with the fuel. The fuel is “sucked” into the engine due to a physical phenomenon known as the venturi effect, which in turn is governed by the Bernoulli equation.

Without getting too technical, what is happening is essentially a speeding up of the air as it passes through the narrowed gap in the middle of the carburetor. When it does this, the pressure drops, according to the Bernoulli principle. The fuel reservoir is connected to the air outside of the carburetor via a small tube, keeping the air in the reservoir along with the fuel at constant pressure.

Pressure Difference

The second tube that goes from the fuel reservoir into the carburetor is governed by the pressure inside the carburetor. When the gas pedal is pressed, the air through the narrow part of the carb speeds up, dropping the pressure in the carb. This difference in pressure means the higher atmospheric pressure pushes the fuel into the lower pressure carb and then into the engine.

When the gas pedal is released, the valve at the bottom closes which then stops both air and fuel getting into the engine, preventing it from producing any more power until the gas pedal is pressed again. The valve at the top is called the choke valve, and some carburetors feature a manual choke valve or lever, while others operate automatically using a temperature sensor.

Choke Valve

These essentially restrict the air flow into the carb, so that when the gas pedal is pressed a higher amount of fuel is sucked into the engine in proportion to the air, which is useful in cold temperatures due to the way that fuel evaporates and is ignited in the engine. These were very common on motorcycles, but they are not the most important component for this article.

What Is Electronic Fuel Injection?

The Modern Way

Electronic fuel injection (EFI) arrived in the 1980s andhas been used in all modern cars since the mid-1990s. It is a more complex system than the carburetors of the past, but the function is the same. They are what delivers the fuel to the engine, but they do it in a very different way. They use electronics and a high-pressure pump to spray fuel into the engine.

Where exactly the fuel is sprayed depends on the type of EFI system in the car. There are several types of EFI system. Port injection sprays the fuel onto the intake valve that lets the fuel into the engine, while direct injection sprays fuel directly onto the cylinders in the engine. Both have their advantages and disadvantages.

Electronically Controlled

The process is still governed by the gas pedal, but instead of mechanically opening valves and spraying fuel into the engine via pressure differentials, the EFI system takes care of everything using various electrical components. This has its own advantages and disadvantages too, so let’s compare carburetors and electronic fuel injection systems, and find out which is used in NASCAR.

Which One Is Better?

Air : Fuel

Carburetors and fuel injection systems serve the same purpose,but in two very different ways. So, which is better? Let’s start off with carburetors, with the main disadvantage being control over the air to fuel ratio. Fuel burns in air, and so some is needed for proper combustion within the engine. But there is an ideal ratio of air to fuel, which sits at around 14.7:1.

This means that in order to get the best performance and fuel efficiency, this is the mixture that the fuel delivery system should deliver to the engine. Carburetors are made to provide as close to this ratio as possible, as much of the time as possible. But there are lots of things that can affect whether or not this is the case, such as altitude, which in turn alters the pressure within the carb.

Optimization Of This Ratio

Temperatures can also have an effect, and so there is no way for the air to fuel ratio to be controlled with a carburetor, unless it is physically tuned for specific conditions. With EFI systems however, the air to fuel ratio is optimized through its design, with the fuel being injected into the cylinder itself or via the intake valve as described in the previous section.

When it is injected into the intake valve, it has a cooling effect and a cleaning effect. This can benefit the longevity of the engine, but for superior control over the air to fuel ratio a direct injection system is used. There are different types of direct injection system, but as they are injecting the fuel into the cylinder where it will be burned, the ratio of air to fuel can be much more precise and consistent.

Different Types Of Injection

Direct injection also has a cooling effect, but this time within the cylinders themselves. This can help prevent knock, which is unwanted combustion of air that can damage engines. But both types of fuel injection will provide a more precise air to fuel ratio, and they can be made to automatically adjust the amount of fuel injected depending on the pressure and temperature of the air.

These systems can also be installed on each individual piston, which means there is a far more even and consistent distribution of fuel than you would get with the carburetor. But these advantages don’t come alone, as there are some downsides to EFI systems. The main one is the cost, due to the fact that there are far more complex components involved than in a carburetor.

Cost Of Repair

Carburetors work mechanically, and so although they can cause problems and need repairs, they can usually be carried out by the driver if they know what they are doing, but if not, they can be fixed easily and cheaply at a garage too. EFI systems need extensive and careful work to be repaired, and this means they can also cost substantially more than carburetors.

A faulty carburetor might cost a few hundred dollars to repair if you don’t do it manually, with the bulk of this only being necessary if you need a new one. EFI systems on the other hand can easily run into the thousands of dollars, depending on the situation, as well as the make and model of the car. But overall, EFI systems are more efficient, and thus better for performance and the environment.

Does NASCAR Use Carburetors Or Fuel Injection?

Late To The Game

You would think that with the higher efficiency and consistent air to fuel ratios, one of the world’s biggest motorsports would be happy to switch, right? Well, it took until 2012 for the first fuel injection systems to be used in NASCAR, and that was just in the Cup Series. To this day, the Xfinity and Truck Series both still allow carburetors, 25 years after the last new road cars featured them.

Fuel injection systems were outlawed in the entirety of NASCAR until 2012, which is why it took so long for them to be implemented.This was mainly due to tradition, and the fact that the 1957 Chevrolet was very dominant, which used fuel injection, and so it made everything else seem uncompetitive. That is not a situation that any sport wants.

Very High Costs

While this sounds like a sport being (very) slow to catch on to modern innovations, there are plenty of reasons for NASCAR sticking with carburetors for so long. The main one is the high cost of the switch. McLaren were the ones behind the EFI systems to be featured in NASCAR, and it was going to cost teams $26,000 to make the switch from carburetors.

This obviously raises the costs of racing significantly, which makes it more difficult for smaller teams to move forward with the teams with more money. This is the main reason that carburetors have not been outlawed in the other two series. One area where advantage meets disadvantage is in the control of the air to fuel ratios, which makes EFI much more favorable on the road.

Plenty Of Adjustments

In NASCAR, the carburetors allowed for various changes to be made by the mechanics to suit the cars, drivers and the tracks. The total number of adjustments was 24 for carburetors, and forEFI systemsthis multiple more than 6 times over to 150. This gives the crew chiefs a lot of room to change things around, in order to get the maximum performance out of every race car.

But this has a downside. This extra mapping that can be done means that the team needs to be trained well enough to use all of these different adjustments. This training costs money, and it can require the hiring of a new employee to take care of everything to do with the system. Smaller teams don’t always have the budgets to make the most of new technology like EFI, even if it is now fairly old.

EFI Is Better

The advantages do outweigh the disadvantages on the larger scale however, and that is why the transition to EFI was made in 2012. There has yet to be a retirement directly due to an EFI system, and it has even been observed that there have been fewer retirements due to engine failures in the last few years too, hinting at the EFI’s supremacy over carburetor-fed engines.

Final Thoughts

Overall, it could be argued that the transition from carburetors to fuel injection in NASCAR took too long. But with motorsports usually doing their best to keep costs down, it made some sense for NASCAR to keep carburetors until 2012 in the Cup Series, and they are still used in the Xfinity and Truck Series. But fuel injection is clearly the better option, with few teams still using carburetors.