Engineers have solved the technical problems that dogged the three-cylinder engine in the 1980s and early '90s. But even with turbochargers, it may take a while for the triple to outrun its historical baggage.
Six automakers that sell vehicles in the United States have three-cylinder engines on the road or on the way. These new three-bangers are nothing like the wheezing, shaking triples available in economy cars such as the Geo Metro, Subaru Justy and Daihatsu Charade sold here 25 years ago.
The engines in those budget cars were strictly low-tech. They lacked power and refinement, and they delivered painfully low performance.
For example, the 1.0-liter engine in the Charade, sold here from 1988 to 1992, generated just 53 hp and needed an agonizing 15 seconds to propel the 2,000-pound compact hatchback to 60 mph. Perhaps its only saving grace: a respectable 38 mpg highway EPA fuel economy rating.
The 2014 Ford Fiesta SFE, by comparison, shows how technology has transformed the three-cylinder. The Fiesta SFE has the same size engine as the Charade had, 1.0-liter, but it is rated at 123 hp, carries an EPA rating of 45 mpg on the highway and can move the Fiesta -- which weighs 800 pounds more than the Charade -- to 60 mph in less than 8 seconds.
BMW's 2014 Mini Cooper comes standard with a 1.5-liter turbo three-cylinder that generates more power than the outgoing 1.6-liter four-cylinder, chops 2.3 seconds off the 0 to 60 mph time and propels the Mini's miles per gallon into the 40s for the first time.
Ford, BMW and other automakers are not drawing attention to the number of cylinders. That's due in part to the reputation of three-cylinder engines. Instead, their message focuses on performance and fuel economy.
"We haven't discussed it that much," says Patrick McKenna, Mini's product planning manager. "It's not something to tout, but at the same time, it's not anything to be avoiding.
"We put it in the specs, and we are definitely training our motoring advisers at dealerships to talk about all the merits. We really haven't put any special attention to it."
Ford, Mitsubishi and Smart also downplay engine configuration on their consumer Web sites.
Wade Jackson, Fiesta brand manager at Ford, says no ads are planned to point out that the Fiesta SFE has a three-cylinder engine. The car launched in January and is off to a good start. The SFE accounts for between 5 and 8 percent of sales, depending on the region.
"Customers may not see an ad," he said. "The 45 mpg message is being delivered through the dealer network."
BMW makes motorcycles with larger, more powerful engines than what's under the hood of the new Mini Cooper. You can buy lawn mowers with bigger engines than what you'll get in the new Mitsubishi Mirage.
Automakers are turning to threes for a number of reasons: Smaller engines reduce vehicle weight, which improves handling and braking. Also, three-cylinder engines use roughly 20 fewer parts than four-cylinders. And, because the engines are so compact, they can help improve safety in front-end crashes. With more space around the smaller engine, the chances of it penetrating the interior in a severe high-speed crash are reduced.
But most important, three-cylinder engines can deliver diesellike levels of fuel economy for much lower cost.
What is not yet known is how consumers will accept the modern three-cylinder.
"It's all about perception," says AutoPacific analyst Dave Sullivan. "If the engine is rough and vibrates at idle or sounds weak, consumers will feel like something is wrong. But if it is smooth and powerful enough to merge onto a highway with a passenger, consumers likely won't even notice."
McKenna says most Mini buyers have three items on their checklists when they shop: design, performance and fuel efficiency. The last-generation Mini had a 38 mpg EPA highway rating, which, he said, resulted in lost sales because some buyers felt a car of its size should do better.
The 1.5-liter three-cylinder engine gives the Mini with a manual transmission a 42 mpg highway rating.
The high-performance Cooper S still offers a four-cylinder. Mini officials expect sales of the Cooper to remain at about half of total sales.
"A group of customers come to us really seeking fuel economy and [low] cost of ownership," McKenna says. "Sometimes, we lose out to another competitor who has greater fuel efficiency. I think we will be more successful closing these people."
Advances in engine-mounting systems and engine balancing have made three-cylinder engines just as smooth and quiet as many four-cylinders -- even though the odd number of cylinders complicates things.
Because two of the pistons move up and down in the cylinders at the same time, the three-cylinder engine is naturally unbalanced.
Ford tackled the issue in two ways: by designing a patented engine-mounting system that redirects the shaking energy and by using the engine's flywheel and front pulley to cancel out the imbalance. BMW, Mitsubishi and General Motors use balance shafts installed in the engine that rotate in the opposite direction as the crankshaft to cancel out vibrations.
GM is launching its three-cylinder in Europe in the Opel Adam subcompact. Company spokesman Tom Read says the tiny engine could be offered in North America provided fuel economy, refinement and performance meet customer expectations.
In addition to the Mini Cooper, BMW's i8 plug-in hybrid sports coupe will get a performance-tuned version of the 1.5-liter triple.
Toyota announced last month a new engine family that includes a 1.0-liter three-cylinder but has not said in which vehicles it will be used.
Except for the BMW i8, the three-cylinder engine is powering conventional vehicles now. But it also could be ideal for hybrids because of its small size, low weight and high power output.
Still, Sullivan says AutoPacific does not see huge sales for three-cylinder engines right away.
"Sales will increase because we're basically coming from zero," he said. "There will be some more availability, including Mini, which will help to change perception."
Low-speed torque, which enables a car to move away from a stoplight quickly, and wide variations in fuel economy vs. the EPA window sticker are two aspects of the triple to which early adopters will have to adapt, Sullivan said.
The fuel economy on any turbocharged engine varies greatly based on factors such as driver behavior, geography and traffic patterns. The more the turbo is used by a heavy-footed driver, the lower the fuel economy.
Many three-cylinder engines don't generate much of their torque until the turbocharger winds up.
Two of the three-cylinder engines on the market, those used in the Smart car and the Mitsubishi Mirage, are low-tech compared with the Ford, BMW, Toyota and GM engines. They do not have turbochargers or direct fuel injection.
With the Mirage, Mitsubishi's focus was on delivering an affordable entry-level car that offers the fuel economy of a diesel or a hybrid, but at a much lower price. There was no debate about adding a turbocharger or direct fuel injection, said Bryan Arnett, Mitsubishi's senior manager of product planning.
The goal was to reduce the vehicle's overall curb weight to enable the engine to deliver adequate performance. The Mirage weighs just 1,863 pounds and can reach 60 mph in about 11 seconds.
"Cost and affordability were the primary initiatives," Arnett said. "Rather than concentrate on producing more power, we wanted to reduce overall curb weight. We wanted an over-40-mpg car."
If the three-cylinder engine can deliver real-world fuel economy numbers close to the EPA label on the window sticker, it may earn a permanent place in North America. But that's a big if.
Says Sullivan: "I-3 engines seem to do well on the EPA test cycle but require more wringing out by the driver, and fuel economy suffers."