Shifting gears in the all-new 1.0-L EcoBoost Ford Focus illustrates a favorite topic of discussion for powertrain engineers: friction reduction.
This AEI editor experienced it on fast, sweeping, undulating roads in southern Spain, during a recent media preview. Asked why the car’s apparent flywheel effect was so pronounced during upshifts, Dr. Thomas Zenner, Ford’s Supervisor, Three-Cylinder Development, explained that the EcoBoost’s flywheel was certainly not the cause.
“You may have thought it was a heavy flywheel, but it is simply the effect of a small engine with very low friction losses, the speed of which when shifting gears does not reduce as you might expect; it just keeps on going,” Zenner said.
The issue is really psychological. Some drivers, attuned to the combustion events of four-, six-, or eight-cylinder engines, may not appreciate aurally that Ford's new triple is revving as freely as it is.
Low friction is a significant plus in terms of overall efficiency and underlines the performance potential of this moderately boosted, tiny engine that is set to become a central part of Ford's global powertrain strategy. It will launch in Focus and the new B-Max MPV, with future applications likely to include Fiesta, Ka, and C-Max.
Five years in its development from conception to production, the 1.0-L is part of Ford's emerging Fox family. Available only in turbocharged form at first, it is likely that naturally aspirated versions will appear later for some emerging markets, including South America.
Initially offered in 73.5- and 92-kW ratings (98.5 and 123 hp, respectively), it replaces a 1.6-L four-cylinder naturally aspirated gasoline unit in the Focus. The downsized triple improves fuel efficiency by up to 20% but provides similar top speed and acceleration. Its dressed weight is 97 kg (214 lb); power density is greater than that of any Ford engine to date.
The block is an iron casting, and its "footprint" is so compact that it fits within a sheet of A4 paper. Although cast iron would seemingly be a disadvantage compared to aluminum, Zenner said that the engineering teams had managed to create a block that was “competitive” in terms of weight with that of aluminum, while offering significant advantages regarding warm-up and reduced friction.
Maximum torque of both power output versions is 170 N·m (125 lb·ft)—10 N·m (7.3 lb·ft) better than the 1.6-L. The EcoBoost’s torque curve is remarkably flat, producing the maximum figure from 1400 to 4000 rpm for the 73.5-kW version and 1400 to 4500 rpm for the 92-kW version, the latter having a 200-N·m (147.5-lb·ft) transient overboost capability.
New Continental boosting system
Claimed performance figures for the Focus five-door equipped with the 92-kW engine and six-speed manual gearbox (curb weight: 1279 kg/2820 lb) are as follows:
Top speed: 193 km/h top speed (120 mph)
0-100 km/h (0-62 mph) acceleration: 11.3 s
50-100 km/h (31-62 mph) acceleration: 10.8 s
Combined fuel consumption: 5.0L/100 km; 114g/km CO2.
Ford claims the Focus with the 73.5-kW engine achieves CO2 emissions of 109 g/km.
Power density was the biggest single R&D task of the 1.0-L program, noted Zenner. “To achieve that and make this very compact engine durable was quite a challenge, in particular for the cylinder head," he explained. The long-stroke dimensions (71.9 x 82 mm) are good for knock mitigation, torque, and overall packaging. The 6.1-mm (0.24-in) bore bridges include a cooling slot, Zenner noted.
The two most advanced areas of the engine’s technology cited by Zenner are its exhaust manifold that is integrated into the cylinder head casting and its internal timing belt that runs in a bath of engine lubricant. The manifold saves nearly a kilogram (2.2 lb) of weight, accelerates engine warm-up, and enables stochiometric operation in the whole operating range. The belt-in-oil primary drive reduces friction and noise compared with a conventional "dry" timing drive.
Zenner also explained that although a balance shaft might be expected in a three-cylinder engine, Ford engineers decided to intentionally unbalance the flywheel and crank pulley in conjunction with mounting optimization, to offset the primary engine shaking forces into a less sensitive direction. (The 1.0-L crankshaft's throws are offset at 120°.)
“But really for this engine it would be unfair to just point to a couple of things, however significant,” he explained. “We have more than 15 engineering actions in the engine, each giving a percentage point or more to enhancing fuel economy.”
One of these is the low-inertia Continental turbocharger designed and developed specifically for the 1.0-L EcoBoost. It can spin up to 248,000 rpm and has a 38-mm (1.49-in) diameter turbine.
“It is almost fantastically small for the output it gives,” noted Zenner. “It has a vacuum- operated wastegate, which gives us complete flexibility in how and when to operate it—for example, to completely open it at part load to reduce pumping losses. That provides a couple of percentage points in fuel consumption bonus.”
To prevent pressure from rising too steeply at high engine output, a wastegate valve conducts the exhaust gases past the turbine, explained Udo Schwerdel, head of Continental's turbocharger product line. On the compressor side, a compressor bypass valve prevents air, which has already been compressed, from forcing its way back into the compressor housing when the throttle closes, safeguarding against compressor surge and possible damage.
Working together, Continental and Ford also have managed to obviate the need for additional enrichment (resulting in high fuel burn) to control turbo temperatures. The integrated exhaust manifold cools exhaust gas, and the turbo’s turbine has been developed to withstand temperatures of up to 1050ºC. Some turbos have a 1000ºC limit, and from about 3000 rpm, they need extra fuel for cooling, stated Zenner.
The 1.0-L engine has a "soft" electronic limiter action at 6500 rpm. The tachometer in the Focus is red-lined from 7000 rpm, but the engine still feels smooth and has a fine aural signature at high revs.
Timing belt bathed in oil
Although engineers said more power could be extracted, the raison d’être of the power unit is very much about optimum power/torque/fuel consumption balance.
As experienced by this AEI editor on Ford's lengthy test route, turbolag was minimal. To quantify that subjective assessment, Zenner said, "At 1500 rpm, it takes 1.5 seconds to achieve 90% or torque. That is about half what might be expected.”
A special engine oil has been developed for the 1.0-L unit in collaboration with BP. It is very low friction but meets 20,000-km (12,427-mi) service interval requirements. It is likely to be more expensive than a regular oil but a vehicle owner would see “a quick payback” via fuel savings, according to Ford.
Other elements of the friction-reduction program for the 1.0-L include specially coated pistons, low tension piston rings, and low friction crankshaft seals. An ECU-controlled variable displacement oil pump provides on-demand lubrication. Running the cambelt in an oil bath also improves refinement.
Separate cooling circuits for cylinder head and block facilitate a faster warm-up, making the engine only some 7% less efficient when cold compared to 10-12% for a typical ICE. The 6.1-mm gap between cylinders also aids warm-up.
An added difficulty with the introduction of radically different powertrain solutions is increased cost. The 1.0-L EcoBoost is more expensive to build than a regular four-cylinder (partly due to the latter’s achieved economies of scale) but not as costly as a diesel, Ford engineers said.
The new engine will be built at Ford’s Cologne plant, which has a production capability of 350,000 units per annum. The facility, which previously produced V6 engines, has been upgraded at a cost of 134 million euros for production of the EcoBoost. Among its improvements is MQL (minimum quantity lubrication), a "dry" machining process that significantly reduces the amount of coolant needed to machine EcoBoost cylinder heads (see http://www.sae.org/mags/aei/7205).