It was on a sparkling, sub-zero Ohio morning last winter that I really learned to appreciate electronic fuel injection. It was so cold that I could hardly turn the key in the frozen door lock of the new subcompact. Once inside, my breath instantly frosted the windshield. But when I slipped the key into the ignition and twisted, the engine cranked for only an instant before revving smoothly, if a bit stiffly, to a fast idle.
I hadn’t pushed the accelerator pedal to set the choke, much less pumped it furiously to prime the engine, as I would have done or some cars. I just turned the key, and it started. A few seconds later I eased out the clutch, gave the engine a little gas, and the car pulled smoothly onto the street, snow squeaking under the tires. It didn’t buck, hesitate, or stall once. The reason? Electronic fuel injection. Like most drivers, I used to think of performance cars when I thought of fuel injection: Ferraris, Corvettes, and Porsches. True, Volkswagens and some lower-priced imported sedans have been equipped with fuel injection since the late 1960s. But suddenly it seemed as if every U.S. maker was adding it to its everyday economy cars–cars like the Chevrolet Citation, Dodge 600, and Renault Alliance.
Why the sudden switch? I had certainly discovered at least one benefit of electronic fuel injection: better cold starting and smoother warm-up. But what else does this technology offer? What will the changeover mean for the average driver and for the U.S. auto industry?
One place I looked for answers was the Rochester Products Division of General Motors. For decades the name Rochester has been almost synonymous with carburetors. But now the company is rapidly becoming one of the world leaders in fuel-injection technology. Few people realize that Rochester has been involved for many years in the development of electronic fuel injection.
“In 1970 we worked on an electronic multi-point fuel-injection system,” recalls Roland S. Taylor, chief engineer for gasoline and emissions-products design. “But we were unsuccessful as far as the marketplace was concerned. You couldn’t justify the cost because you had to buy the electronics. The carburetors won out because they gave adequate performance for the least cost.” Tipping the balance
It wasn’t long, however, before the new clean-air standards began to tip the balance. To control exhaust emissions, the air-fuel mixture fed to the engine had to be precisely controlled. If too rich (too much fuel and not enough air), emissions of carbon monoxide and unburned hydrocarbons soared. If too lean; oxides of nitrogen and engine misfiring became a problem.
If the air-fuel mixture could be tightly controlled, exhaust emissions would be kept low enough so that a catalytic converter in the exhaust system could handle the light cleanup. But a typical engine operates under a wide range of temperatures, loads, and altitudes, all of which require subtle changes in the mixture ratio. Toward a solution
Then, in the mid-1970s, two break-throughs promised a possible solution to the mixture-control problem. The first, the inexpensive microcomputer, needs no further introduction. The second, the oxygen sensor, is less famous but almost as amazing. This hollow, platinum-plated ceramic probe can measure the oxygen level in the blazing 1,112-degree-f exhaust gas and then tell the computer whether the engine is running lean or rich.
If the air-fuel mixture is rich, there will be little oxygen left in the exhaust gas. Oxygen ions flow from the inside surface of the probe–which is exposed to the atmosphere–to the outside surface exposed to the exhaust gas. Just an in a one-cell battery, this ion flow generates a voltage (in this case about one volt).
When the mixture is lean, however, and there is oxygen in the exhaust gas, the ion flow slows, and the sensor output drops to nearly zero.
At first the engineers used the oxygen sensor to fine-tune the carburetor while the engine was running ["Feedback-Carburetor Systems," PS, Sept. '82]. The voltage signal from the oxygen sensor, along with data from sensors measuring engine temperature, speed, and manifold vacuum, was fed into the on-board computer. An input signal from the computer then adjusted a mixture-control solenoid in the carburetor body. However, because a carburetor is a maze of separate air and fuel circuits, this closed-loop control, as the engineers call it, is still something of a compromise.
“We went through the whole closed-loop interim because that was all we really had,” says Taylor. “We had to respond very rapidly to the emissions standards. But we really felt that the carburetor wasn’t the best way to meet the standards.”
Moreover, the carburetor was growing increasingly complex, even without the addition of electronics. Owners were starting to complain that cars were hard to service and sometimes didn’t run well no matter how often they were fixed. And because of the closed-loop systems, many cars already had small microprocessors tucked under the dash. A love affair
Engineers love electronic fuel injection (So, I will recommend you to check out this great online resource to learn about fuel injector cleaner or amazing solutions of how to clean fuel injectors in the right way). The first time I picked up an injector–the part that actually meters the fuel into the engine–I understood why.
The injector is nothing more than a solenoid-operated valve, small enough to fit in the palm of your hand. Although some precise machining is involved in manufacturing the valve, its operation is simplicity itself. There are inputs–information from sensors that measure things like engine temperature, load, vehicle speed, and exhaustgas oxygen content. A program in the computer under the dash or in the kick panel then calculates the precise amount of fuel needed to give near-perfect combustion and sends a pulse of current to one or more fuel injectors. Supply the injector with fuel under pressure, zap the solenoid coil with about six volts of direct current, and you get precisely metered fuel. The length of the electrical pulse determines the amount of fuel.
“By switching to fuel injection and controlling one variable–the length of the injector pulse–we were able to do all of the things we needed to,” Taylor explains. “Cold-start, warm-up, warm-running, power-enrichment, and altitude compensation–all of these can be done by simply adjusting the pulse width.” Not only did more-precise fuel metering reduce exhaust emissions, it also did wonders for drivability.
Like General Motors, Chrysler also sees a big future for fuel injection. The company plans to switch its entire passenger-car line to fuel injection by 1986 or ’87. “Why electronic fuel injection? Drivability–clean drivability,” Bernie Robertson, chief engineer for power-train systems, emphasizes. “It does give us some fuel economy. It does give us better performance. But the primary motivation is drivability and performance feel.” Two systems
In the switch to fuel injection at Chrysler and elsewhere, two basic systems have emerged. The first, called throttle-body injection, bolts onto a conventional intake manifold and looks much like the familiar carburetor. The throttle-body casting carries one or two injectors (depending on the fuel demands of the engine), a fuel-pressure regulator, an idle-speed control motor, and a sensor to tell the computer how far open the throttle is.
The second type, called multi-point, uses a separate injector for each cylinder. A throttle body in the intake passage houses the throttle plate, the idle-speed control motor, and some type of sensor to tell the computer how much air is being swallowed. But the intake manifold carries only air, not an air-fuel mixture as in a carburetor or throttle-body-injection manifold. Fuel from the individual injectors is sprayed onto the back of the hot intake valves just as the air enters the cylinders. This not only cools the valves but also ensures that the fuel is completely vaporized.
Each type of fuel injection has its advantages. Essentially, throttle-body is cheaper, and multi-point gives slightly better performance.
“There will be a division just like the one you used to see between two-barrel and four-barrel carburetors,” Taylor predicts. “The car you drive to the drugstore and use to carry the kids to school–that’s going to be a throttle-body car. On heavier cars, luxury cars, and sports cars, you’ll see multi-point.”
Multi-point provides better performance because it allows careful tuning of the shape and size of the intake manifold. Passages up to a foot long are often used to give good horsepower and torque at normal driving speeds.
“If you try to do that with a carburetor or throttle-body injector, you get long transport time. Some of the atomized fuel drops out into liquid form again, which can result in poor warm-up performance,” explains Taylor. “You can add heat to the manifold to keep the fuel from condensing, but you lose power because the volumetric efficiency [the amount of fuel and air entering each cylinder] drops.”
Multi-point is also used with turbocharged engines for similar reasons. Again, the engineers need not worry about transporting vaporized gasoline through the intake passages. Instead they can concentrate on designing the turbocharger system to deliver exactly the right amount of compressed air for each driving condition.
All three of the major domestic car makers sell both throttle-body and multi-point systems. U.S.-built Renaults use a Bendix throttle-body system for cars sold in 49 states and a Bosch multi-point system on those destined for California, where emissions standards are tougher.
In addition to the technical change involved, the switch to fuel injection is also bringing a new multinational supplier to the U.S. Bosch, which made its fame and fortune building sophisticated multi-point systems for European cars, sees America as a growing market for its products. Ford, Chrysler, and GM use Bosch injectors and other components in their mutli-point systems. Bosch also builds the throttle-body injection used by Chrysler and supplies injectors used by Ford in its Throttle-body unit.
Other injection-system parts for U.S. cars are being built by traditional suppliers to Detroit. The heart of the system, the computer, is built by each manufacturer for its own model line. Such a mixture of domestic and foreign sources might have been frowned upon at one time, but no longer. As one engineer for a U.S. car maker said recently, “We’re going to use the best that’s available in the world.”
And what about servicing these electronic wonders? Many mechanics have encountered problems working on the newest electronic fuel-injection systems. After all, they’re part of a strange new world, complete with sealed black boxes and sensitive sensors. And although the electronics are usually reliable, when one of the parts does break or malfunction, it can cost a lot more than an old-fashioned tuneup. But for the mechanic who learns the ropes, these systems can be far simpler and more logical than the complicated emissions controls and carburetor they replace. An added bonus is the self-diagnostic function that most of the computers possess, which checks not only its own function but also that of its sensors.
And while the jury is still out on the long-term durability, the auto makers seem happy. “We’re seeing much better customer satisfaction and a lot fewer warranty claims,” says Taylor. “Though that still doesn’t say you can’t do a botch job of it.”
Every engineer I spoke with predicted that electronic fuel injection would replace the carburetor on passenger cars within three years. Only one could think of a car that would keep its carburetor. A holdout
At Ford’s Service Research Center in Dearborn, Mich., a service engineer and I were going over service changes for the 1984 cars. I couldn’t help noticing the sleek fenders and slippery body panels that made up the front-end test models for the 1985 and later cars. Nestled inside were four-cylinder and V6 engines, each wearing the tell-tale aluminum air box that could only mean fuel injection. So I asked the engineer whether any Fords would still have a carburetor a year or two down the road.
“The use of fuel injection will be expanded,” he predicted. “The major exception will be the Mustang GT.”
I was puzzled. Why would Ford stay with a carburetor on such a high-performance car? Anticipating my question, the engineer smiled at me and continued.
“We think the person who buys that car is someone who likes to tinker on the weekends,” he said. “And we think he will be more comfortable with the old familiar Holley four-barrel.”