Carburetors vs. Fuel Injectors and NASCAR

Unless you’re buying a vintage 1970s model, chances are that weighing the pros and cons of carburetor vs. fuel injection system isn’t part of the car-buying equation. While fuel injection technology has become standard for consumers for the better part of the last three decades, electronic fuel injection (EFI) is a new technology to the NASCAR circuit. As the first EFI-powered season draws to a close, it seems the change has been an overall well-received one.

Out with the Old…

Cars powered by a combustion engine, no matter what year they were built it in, need two things to go: fuel and air…in the right proportions. Carburetors are yester-year’s technology to manage the intake of fuel and air into the engine to improve performance.

Carburetors rely on Bernoulli’s Principle of fluid velocity and pressure for performance. Air intake through a venturi-shaped pipe creates a vacuum that draws fuel into the chamber, and the air-fuel mixture is then introduced to then engine for actual combustion.

For optimal performance, engines require a certain air:fuel ratio. Too much air and not enough fuel = sputtering. Too much fuel and not enough air = flooding. Various valves and mechanisms within the carburetor serve to control the amount of air or fuel allowed into the intake manifold to achieve the optimal air:fuel ratio, and thus, optimal engine performance.

However, the fuel-air mixture exiting the carburetor feeds all engine pistons. The valves and chokes used to adjust the intake can only control the total air or total fuel allowed into the engine chamber, not the air:fuel ratio feeding individual pistons.

Because carburetors have no electronic components, adjusting the carburetor—the timing of valves and opening of chokes—had to be done by ear…hence the term tune-up.

For over 60 years, NASCAR has relied on carburetors and engine builders with a fine tuning ear to maximize their performance…until now.

…In with the New

Electronic fuel injection systems do essentially the same thing that carburetors do, they just do it for each individual piston and with an electronic monitoring system to ensure a consistent air:fuel ratio to deliver maximum engine performance.

There are several different types of EFI systems, the variation primarily being where and how much fuel is injected into the engine chamber. All EFI systems, however, collect data about engine conditions in order to automatically adjust air:fuel ratios, injection flow rates, etc.

It is precisely the access to measurable data that has the majority of NASCAR crews stoked about the switch to EFI in the 2012 season.

Better Than Mixed Reviews

With the 2012 racing season nearly complete, most NASCAR teams, particularly the engine builders and crew chiefs, have positive feedback regarding the carburetor to EFI transition. Some, including engine builder Doug Yates, CEO of Roush Yates Engines, have looked forward to the challenge from the get go: “It’s very exciting from an engine builder and an engineer’s perspective, having new technology in NASCAR. And it’s our job to hopefully make it seamless.”

While there have been some hiccups in the early races (remember Phoenix and Las Vegas?), teams have worked hard to make adjustments…and just which adjustments need making have been both surprising and easier to pinpoint with the EFI data and on-track observations.

As Jeff Andrews, Hendrick Motorsports director of engine operations, points out: “The conditions inside of the car and under the hood—and all of the things that go on during the weekend, whether it be restarts or pit stops, temperatures and brief overheating periods—these are all things now the engine management system reacts to. Once you start throwing seven [engines] out there every weekend, your sample rate goes up dramatically. And so does the likelihood of what we like to refer around here as ‘new challenges.'”

But analyzing the data available via EFI also allows teams to “diagnose the failure rather than presume something,” as noted by Ron Sperry, components design engineer for GM Racing Group. And, with real information about engine conditions, Andrews believes “you can make a better engine down the road because you understand better what the operating conditions are. The information will make us better.”2

In addition to improving racecar performance, NASCAR’s transition to EFI may also provide an opportunity for auto makers to once again use the race track as a new testing ground for new technologies.