When Ford launches the 2014 Fiesta in North America early in 2013, one of the engine choices will be a three-cylinder, the one-liter EcoBoost. The company is betting big that consumers will embrace it.
Three-bangers aren’t really new to the American market. They’re common in motorcycles. Elmore offered a three-cylinder auto way back in 1905, and sporty car buffs will remember the two-stroke triples offered by Saab and DKW in the 1950s. More recently, the Suzuki-derived Chevy Sprint/Geo Metro vehicles, favorites of the high-miler cult, featured Suzuki’s one-liter G10 inline three. The first-gen Honda Insight hybrid (2000-2006) also used a one-liter triple, as does the current Smart ForTwo peashooter.
What Ford hopes to achieve with its new 1.0L Ecotec is mainstream acceptance and a whole new respect for three-cylinder engines. Good fuel economy is a given, thanks to dinky displacement and the lower frictional and mechanical losses of three cylinders versus four, ditching roughly 25 percent of the moving parts. That’s on the plus side.
Where triples have traditionally fallen short with the car-buying public is in performance, engine life, and NVH (noise, vibration, and harshness). The problem starts with basic mechanics: A four-stroke three delivers only three firing impulses every two crankshaft rotations, producing large torque reversals and torsional vibrations (TVs in engineer lingo).
While we think of a crankshaft as stiff and solid, it might be more helpful to regard it as a large spring, winding and unwinding while combustion and other loads are fed into it. So when the torque pulses are few, uneven in magnitude, or unequally distributed, engine roughness is the result.
Ford Fiesta EcoBoost 1.0L three-cylinder engine
Ford attacked the three-cylinder problem on multiple fronts. First, performance: the EcoBoost strategy employs a turbocharger to boost output to a four cylinder-like 123 hp and 148 lb-ft of torque (rpm figures TBA). Ford engineers say this is the second-highest specific torque rating (units of torque per units of displacement) of any current production engine. The turbo employs a tiny rotating assembly with extremely low inertia, spinning at up to 248,000 rpm. To further minimize boost lag and optimize throttle response, the fist-sized turbo is mounted on a short-runner exhaust manifold integral to the cylinder head.
Next, the engine has been shrunk to the smallest size and weight possible. Here’s a neat stunt: a Ford guy walked a bare 1.0L block through airport security in his carry-on bag (photo below). The block is cast iron and fully skirted, yet weighs only 52 lbs. Fully dressed, the engine weighs just 97 kilograms (214 pounds).
Ford EcoBoost 1.0L bare block
This compact architecture results in a crankshaft that is extremely short, stiff, and light, which permits effective external balancing via the flywheel and front damper. In the battle to make its inline three smooth, Ford toiled to avoid using a balance shaft, which adds weight and friction—counterproductive to the engine’s low-mass, ultra-low friction engineering strategy.
Low-drag bearings are used throughout, along with low-friction ring packs. Additionally, the crankshaft is offset 8 mm from the bore centerline, which according to Ford reduced engine friction three to five percent percent due to reduced cylinder wall drag. (In recent years Honda is the champion of this ancient trick, used on the original 1932 Ford flathead V8 among others.)
EcoBoost 1.0L assembly line, Ford Cologne plant
Other cutting-edge features used to wring the final bit of efficiency from the EcoBoost I-3 include direct fuel injection, a variable-displacement oil pump, and a twin-path cooling system with separate pumps for the block and head. Camshaft drive is by belt, which runs in oil to optimize NVH and service life—no replacement interval required.
Introduced in Europe earlier this year, the EcoBoost 1.0L Fiesta has not yet completed EPA testing, but Ford expects the car to deliver the best fuel economy numbers of any non-hybrid in North America. “Many customers would like the fuel efficiency of a modern diesel or a hybrid, but can’t stretch their budgets to cover the cost premium,” says Joe Bakaj, Ford vice president of powertrain engineering. “That’s where the EcoBoost Fiesta fits in. It will offer a highly fuel-efficient alternative at a lower cost.”
No prices have been announced for the Ecoboost Fiesta as yet, but on the rest of the Ford Ecoboost turbocharged engine family, which includes 1.6L and 2.0L fours and a 3.5L V6, the price premium is in the $1000 USD range. Total Ecoboost production recently surpassed 500,000 units.
Of course, the real key to the EcoBoost three’s success in North America will be in what the driver doesn’t hear or feel. “Most customers are not going to be thinking about the number of cylinders under the hood when they drive the new 1.0L EcoBoost Fiesta,” says Bakaj. That’s the plan, anyway.