Driven by a constant need to promote healthier air and better fuel economy, the automotive industry has universally decided that fuel injection is the only option available. The last carbureted production cars were produced in 1990, and nothing we’ve heard from the industry indicates that they’ll ever come back.​

But most fans of high-performance supercharged cars and trucks couldn’t care less about gas mileage. We appreciate cars not because they get us to work on Monday, but because they go fast. So when you decide to build a fast car, you might be faced with the decision to choose between fuel injection and carburetion. But which one is better for supercharging, and why?

Carburetors are generally simpler in theory and operation than EFI systems, but they depend a great deal on atmospheric conditions. One example of this dependence is in the float bowl, where atmospheric pressure must be maintained for proper fuel flow. As the level of fuel changes, the atmospheric pressure in the bowl is maintained by special vent tubes, usually extending into the throat of the carburetor. Because the fuel in the bowl is at atmospheric pressure, it cannot flow into an area of higher pressure. So mounting a supercharger upstream of the carburetor defeats the entire system by eliminating vacuum. For this reason, mounting a supercharger on top of your existing carburetor would require encasing the entire carburetor in an airtight box, where boosted air pressure can replace atmospheric pressure.

Of course, this is why many carbureted systems have the carb mounted before the supercharger, in what is called a draw-through system. While this solves the problems associated with atmospheric pressure, it still comes with at least 2 disadvantages. First, the lack of vacuum in a pressurized intake interferes with the proper operation of the carburetor power valve. Typical carbs, designed for use in N/A systems, can be modified to correct this by manifold referencing the power valves or plugging them entirely. Another option is to purchase a racing carb that has been specifically designed for use with forced induction engines, as these will come with manifold-referenced power valve(s).

The other big problem with mounting a carb upstream of the supercharger is that the air/fuel mixture coming from the carb can be—and often is-- ignited by the heat of the supercharger.

On the other hand, EFI systems don’t depend on atmospheric pressure to operate. The fuel is forced into the engine under pressure in a closed system independent of the atmosphere. This not only increases the stability of the fuel flow, it allows for electronic control over the air/fuel ratio under varying atmospheric conditions. With an EFI system, all of the engine’s operating parameters can be recorded, analyzed and improved upon even years after the readings were taken. EFI systems are also capable of compensating for varying conditions while the vehicle is operating. This is in direct contrast to a carburetor, which will require you to pull over for most adjustments, even minor ones.

Nearly two decades after the mainstream automotive industry had moved past the carburetor, even NASCAR finally embraced fuel injection in 2012. A good portion of the pressure to make the change came from the automotive industry, who relies on racing experience for innovation, and who believes that consumers prefer seeing cars more like their own on the track. But even NASCAR admits that the change to EFI has resulted in fewer engine failures during a race, and racing teams have made the adjustment without any major problems. Master engine builder Doug Yates of Rousch-Yates embraced the change as well, calling the older carbureted systems “antiquated.”

EFI offers a number of advantages over carburetion in a racing environment, including the ability to better adapt to changing track conditions.

In a hard left turn, for example, when the centrifugal force tends to direct more of the fuel toward the right-hand side of the engine, the cylinders on the left-hand side of the engine receive less fuel. This means an increased chance of developing a dangerously lean condition. As a result, the fuel must be metered a bit on the rich side to avoid detonation. Furthermore, this rich mixture is used throughout the race and robs precious fuel economy.

On the flip side, a multi-point fuel injection system delivers a separate fuel charge to each cylinder, and is thus immune to the effects of centrifugal force. The more precise delivery of fuel results in the ability to run a leaner mixture without fear of detonation and make fewer pit stops for fuel. If that isn’t enough, remember that the middle cylinders—numbers 3, 4, 5, and 6 in an 8-cylinder engine—don’t cool as well because they’re sandwiched in between the corner cylinders. Hotter cylinders require more fuel than cool ones, and fuel injection can compensate for the extra demand because each cylinder gets its own fuel supply. The single large injector in a TBI system does not have these advantages, however.

Speaking of fuel supply, most carburetors will need to be modified to run anything higher than 5% ethanol. The current ethanol standard of 10% is already set to change as the ethanol industry—and the EPA-- is pushing for E15 and E20 gasoline, which contains enough alcohol to quickly turn a carburetor float into silly putty.

There is still a very healthy interest in old-school hot rodding, where die-hard enthusiasts focus on a back-to-basics approach to the beloved pursuit of high-end performance. Cars built during the “golden age” of hot rodding benefit from ladder bars, Mickey Thompson 50’s and Holley Double-pumpers. In these cars, old-school carburetors are the only way to go. For the old school backyard hot rodder, there is something sickening and alien about hooking your ’49 Mercury Coupe to a laptop computer, and rightfully so: Being able to tune your engine to deliver mind-blowing performance using only your experience and feel for the motor is a fine art that suffers from technology rather than benefiting from it. This is the nature of art, and for many, hot rodding is an art.

But for sheer performance and precision, you just can’t beat fuel injection. Old school carburetor enthusiasts who have spent a lifetime becoming an expert at carb tuning will probably want to argue the point, but the fact remains that technology is threatening to relegate all of that wonderful knowledge and skill to the realm of automotive trivia. Like solid rubber tires and hand-crank engines, the carburetor has been replaced with a system that simply works better and is more reliable on any car, supercharged or not.

By Vanessa Wilson