Packing 123 Horsepower Into 3 Cylinders

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DETROIT -- Craig Daitch needed to fly to Los Angeles on short notice, and he had more than the usual amount of baggage.

In addition to a laptop and extra clothes, Mr. Daitch, manager for car communications at Ford Motor, was bringing an item for display at last fall's auto show: the largest part of a new Ford engine.

Typically, that cylinder block would be crated and shipped as cargo, with loading handled by forklift drivers. But this time Mr. Daitch stuffed the engine block into his suitcase and checked it onto the flight after passing through airport security.

At 52 pounds, the cast-iron block of Ford's new 1-liter EcoBoost engine is a bantamweight among automobile power plants. (Mr. Daitch didn't even incur an overweight bag fee.) With the total capacity of its three cylinders equal to the volume of a large soft-drink bottle, it's also tiny: placed upright on a desk, the block fits easily within the edges of a file folder.

The compact dimensions of 3-cylinder engines, together with fuel efficiency and reasonably good performance, have pushed Ford and a growing list of competitors -- including Audi, BMW, Citroën, Mini, Peugeot and Volkswagen -- to introduce a new generation of triples, as they are often called.

"Turbocharged 3s are now replacing nonturbo 4-cylinder engines, just as fours have been replacing 6s," said Eric Fedewa, an IHS Automotive analyst who tracks powertrain trends. He explained that in the new 3-cylinder engines, the combination of a turbocharger and features like direct fuel injection and variable cam timing "effectively serves as a fourth cylinder."

The overall effect is to transform the 3-cylinder Davids into aspiring Goliaths. Ford's diminutive and technically sophisticated triple will be offered in the 2014 Fiesta in the United States. Its performance -- 123 horsepower and 148 pound-feet of torque -- is the highest power output for its displacement of any Ford production engine, the company says.

While offering the triple in the 2,600-pound Fiesta subcompact was a logical move, Ford surprised the industry by announcing it would make the engine available next year in the 3,350-pound Mondeo, the European version of the Fusion. (It is already offered in the European C-Max.)

In the five-passenger Mondeo sedan, the 1-liter triple stretches the limits of how small an engine will adequately power a vehicle. The combination works, Ford engineers say, because the EcoBoost engine produces 90 percent of its maximum torque at a relatively low 1,500 r.p.m.

Of course, small engines in larger cars are more common in Europe, where a gallon of gasoline costs up to $8 and Fiat even sells a 2-cylinder version of its 500 model. Ford aims to achieve best-in-class fuel economy, the equivalent of about 43.5 miles per gallon, when the Mondeo equipped with the 1-liter triple and a 6-speed manual transmission goes on sale, probably next year.

Ford's success with the Mondeo could help influence similarly radical combinations across the industry, Mr. Fedewa said, even in the United States.

Worldwide, 3-cylinder engines are best known from their wide use in motorcycles since the late 1960s by BMW, Honda, Kawasaki, Suzuki and Triumph, among others. In bikes, the triples fit neatly between 2- and 4-cylinder models.

Their revered performance in the bike world contrasts with the buzzy, underwhelming triples that soured many buyers of econoboxes sold by Daihatsu, Subaru and Suzuki in the 1980s.

Indeed, as automakers downsize their engines and coax more power from fewer cylinders, they're also challenged with making them run as smoothly and quietly as the engines they are replacing. The natural up-and-down shaking forces are more pronounced in engines with fewer cylinders.

Another problem is so-called second-order vibration, according to Joe Bakaj, Ford's vice president for powertrain engineering, caused by the constantly changing angle of the connecting rods as the crankshaft rotates.

The trick for designers is to minimize the natural vibrations occurring at different engine speeds by achieving balance, as much as possible, among the rotating and reciprocating parts.

The task of making a triple with a high level of refinement is not simple, Mr. Bakaj said.

"We calculated that to replace the 1.6-liter engine required just 1 liter with the EcoBoost, but to do a 1-liter with 4 cylinders meant 250 cc per cylinder," he said. "With that size, the ratio of cylinder volume to surface area is too big, so we'd lose much of the combustion energy to heat. We'd lose efficiency."

Ford engineers settled on 300 cc for each cylinder, with a long piston stroke, which helps to minimize the engine's overall length. The short cylinder block helps to reduce what engineers call a rocking couple, which Mr. Bakaj described as the engine's tendency to rock end-to-end along its longitudinal axis as the crankshaft rotates.

Ford's clever use of an unbalanced flywheel and pulley at opposite ends of the crankshaft smooth out shaking, so it does not require a balance shaft, a solution often used in small automotive engines. BMW's new 1.5-liter triple has a balance shaft, which consumes power and adds weight.

The rise of smaller turbocharged engines does not necessarily mean that meeting future fuel-economy standards will be a simple matter for automakers.

In February, Consumer Reports said that its tests of a number of recent models, including the 2013 Ford Fusion equipped with the 1.6-liter EcoBoost 4-cylinder, failed to deliver better mileage and performance than the same models with larger, nonturbocharged engines.

Ford engineers pledge that won't be the case when the 1-liter Fiesta arrives next year. In a test drive of that engine installed in a Focus at the company's Dearborn, Mich., proving grounds, I felt barely any vibration through the steering wheel or pedals when the car idled. There was still no objectionable buzz when I accelerated hard through the gears to 70 m.p.h.

The limited peak power may raise questions about how the 3-cylinder will perform in the much heftier Mondeo, but its noise and vibration levels are, subjectively, equal to or perhaps slightly better than those of the 1.6-liter it replaces.

And the 4-cylinder engine block will not so easily fit in a suitcase.

autonews

This article originally appeared in The New York Times.


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