GM introducing new generation of modular 3- and 4-cylinder Ecotec engines; 11 variants from 1.0L to 1.5L
|New Ecotec 1.0L I-3, 1.4L I-4, 1.5L I-4 engines. Click to enlarge.|
GM is introducing a new generation of Ecotec small-displacement engines (1.0 to 1.5 liters) featuring a modular architecture that broadens its adaptability to global markets and reduces manufacturing complexity while offering customers efficiency, refinement and durability.
GM developed the new engines for the company’s global vehicle portfolio; the engines will power many of the company’s highest-volume small cars and compact crossovers, including the next-generation Chevrolet Cruze specifically tailored for China, which launches in 2014 as a 2015 model. The new engine family, including naturally aspirated and turbocharged variants, will make its way into five GM brands and 27 models by the 2017 model year, said Steve Kiefer, GM vice president, Global Powertrain Engineering.
The new Ecotec portfolio will include 11 engines, with three- and four-cylinder variants ranging from 1.0L to 1.5L—including turbocharged versions—and power ratings ranging from 75 horsepower (56 kW) to 165 horsepower (123 kW), and torque ranging from 70 lb-ft (95 N·m) to 184 lb-ft (250 N·m). The architecture is also designed to support hybrid propulsion systems and alternative fuels.
Development of the new Ecotec architecture was headquartered in Pontiac, Mich., with design and validation shared among the global network of engineering centers. Primary development of the 1.0L three-cylinder variant, for example, was conducted at the Rüsselsheim, Germany facility, which is in the heart of the market for its launch in the Opel ADAM.
Similarly, Shanghai-General Motors in China drove validation of the new 1.4L turbocharged and 1.5L naturally aspirated direct-injection engines that will be offered in the 2015 next-generation Chevrolet Cruze for the Chinese market. GM’s Seoul, South Korea engineering center has taken the lead on calibrating and validating the new Ecotec port-fuel-injection variants.
By 2017, more than 2.5 million new Ecotec engines are projected to be built annually in at least five manufacturing locations around the globe: Flint, Mich. (U.S.); Shenyang, China; Szentgotthárd, Hungary; Toluca, Mexico; and Changwon, South Korea. The Flint facility alone represents an investment of more than $200 million in technology and tooling to support the engines’ production.
|The all-new Ecotec 1.0L turbo, three-cylinder gasoline engine will debut in the Opel ADAM and make as much power as the naturally aspirated 1.6L four-cylinder it replaces while offering an estimated 20% improvement in efficiency. Click to enlarge.|
The first production applications include a 1.0L turbocharged three-cylinder for the Opel ADAM in Europe, and 1.4L turbocharged and 1.5L naturally aspirated four-cylinder engines for the 2015 next-generation Chevrolet Cruze in China.
The turbocharged variants enable the engines to deliver the power and torque of larger-displacement engines with the efficiency of smaller engines. For example, the turbocharged 1.0L three-cylinder used in the Opel ADAM makes as much power as the naturally aspirated 1.6L four-cylinder it replaces along with an estimated 20% improvement in efficiency. As another example, the new 1.4L turbo is up to 5% more efficient than the 1.4L turbo engine it will replace.
The new 1.4L turbo for the 2015 next-generation Chevrolet Cruze in China is estimated at 148 horsepower (110 kW) and 173 lb-ft of torque (235 N·m). The 1.5L is rated at an estimated 113 horsepower (84 kW) and 108 lb-ft of torque (146 N·m). In China, Cruze models with the 1.4L turbo engine will also feature an all-new dual-clutch gearbox.
The new Ecotec engines are calibrated to run on regular unleaded gas—even the high-output turbo variants.
The new Ecotec engines also deliver segment-challenging refinement. GM says that noise intensity is up to 50% quieter than Volkswagen’s EA211 1.4L four-cylinder and up to 25% quieter than Ford’s 1.0L turbo three-cylinder.
Design and engineering details
The new Ecotec engines represent a clean-sheet design and engineering process, leveraging the diverse experience of GM’s global resources.
All variants feature an aluminum cylinder block and head, which help reduce the vehicle’s overall mass to enhance performance and efficiency, while technologies such as central direct fuel injection; continuously variable valve timing; and variable intake manifold airflow complement the efficiency goals with broad power bands for an optimal balance of strong performance and low fuel consumption.
Modularity in parts—such as four-cylinder and three-cylinder blocks—that share bore spacing, bore diameter, liners, block height and other dimensions, reduces complexity and increases the flexibility to quickly adapt the architecture for new applications. Shared rotating parts among several of the variants, as well as common fuel- and valvetrain-system components and other engine-driven accessories, also reduce complexity.
Lightweight and durable foundation. A lightweight, high-pressure die-cast aluminum block is the engines’ foundation, matched with an aluminum bedplate that enhances strength and helps reduce vibration. The high-pressure casting method produces a more dimensionally accurate block that requires fewer machining operations than conventional sand-cast blocks.
For structural stiffness, the block has cast-in-place iron cylinder liners. The bedplate bulkheads also contain cast-in, nodular iron inserts for localized structural stiffness. A die-cast aluminum oil pan contributes additional structural strength.
Each engine features 2.9-inch (74 mm) cylinder bores on 3.19 (81 mm) bore centers and comparatively long piston stroke lengths that contribute to their strong torque. The 1.0L three-cylinder has a 3.0-inch stroke (77.4 mm) and the 1.4L four-cylinder engine has a 3.2-inch stroke (81.3 mm), while the 1.5L four-cylinder has a 3.4-inch (86.6 mm) stroke.
Bay-to-bay breathing, which enhances performance through reduced windage in the crankcase, is enabled through holes cast in the top of the bulkheads and through passages cast where the block and bedplate meet. Cast passages for oil and blow-by management and a 4 mm wall thickness combine to reduce the overall weight of the block assembly, enhancing vehicle performance and efficiency.
Strong rotating assembly. Because of higher combustion pressures and an emphasis on refinement, a premium forged steel crankshaft is used in all turbocharged and naturally aspirated direct-injection engines for strength and low vibration. Port-fuel-injected naturally aspirated variants, which have lower combustion pressures, use a durable cast iron crankshaft with hollow-cast cores for lower weight.
The complementing rotating assembly components include durable powder-metal steel connecting rods and hypereutectic-alloy aluminum pistons that are tough and contribute to quietness. They are used with low-tension rings that reduce friction, which contributes to greater efficiency.
Additionally, the 1.0L variant features a balance shaft mounted inside the oil pan to quell the unique vibration characteristics of a three-cylinder arrangement.
Efficiency-enhancing oiling system. A variable-flow oiling system helps maximize fuel efficiency. Rather than the linear operation of a conventional fixed-flow pump, it is accomplished with a crankshaft-driven oil pump that matches the oil supply to the engine load. The pump changes its capacity based on the engine’s demand for oil. This prevents using energy to pump oil that is not required for proper engine operation.
The flow volume of the oil pump is designed to support the oiling requirements for piston cooling and camshaft phasing. The cam phasers are supplied with oil through separate bores in the cylinder block and head. The recirculation of the increased amount of oil in the cylinder head is permitted through additional pre-cast oil return channels.
Piston-cooling oil jets are used to minimize piston temperatures, helping to optimize performance, efficiency and emissions. The jets are part of the engine’s oiling circuit, mounted at the bottom of each cylinder, and spray engine oil at the bottom of the pistons.
The balance shaft for three-cylinder variants is integrated with the oil pump.
Integrated DOHC cylinder head and exhaust manifold. The new Ecotec engines feature an integrated aluminum cylinder head/exhaust manifold, which further reduces weight—an attribute that contributes to increased vehicle efficiency and a more favorable front-to-rear weight balance, for a more responsive driving experience.
The cylinder head features a water-cooled exhaust manifold integrated within the aluminum casting. Its single-piece design provides a number of benefits, including quicker engine warm-up, which contributes to better emissions performance. It also enhances durability by eliminating the need for gasket sealing around the exhaust ports, as well as offering under-hood packaging advantages.
Dual overhead camshafts, operating four valves per cylinder with low-friction, hydraulic roller finger followers, are hollow in sections to save weight, and are driven by a timing chain with automatic hydraulic tensioning. Aluminum cam phasers enable variable timing for the opening and closing of the inlet and exhaust valves, optimizing fuel consumption and performance under a wide variety of engine load conditions.
A hard-mounted aluminum cam cover features an integrated oil separation system, which serves as the main body for the engine positive crankcase ventilation system—an essential contributor for optimal combustion control. Passages integrated in the cylinder block and cylinder head enable flow of blow-by gases from the crankcase into the oil separation chamber, as well as drainage of the separated oil back to the crankcase. The cam cover assembly also incorporates the oil control valves for the cam phasers and camshaft position sensors. The unique combination improves packaging in the engine and reduces complexity of the cylinder head.
More-precise central direct injection. Central direct fuel injection is used on some of the new Ecotec engines and is a primary enabler of their balance of performance and efficiency. The central location of the six-hole fuel injector, directly above the piston head (held at a narrow, 6-degree angle), further enhances the advantages of direct injection by delivering a more precise and even spray pattern—particularly with the four-valve-per-cylinder arrangement of the cylinder head. This enables the flow rate of the injectors to be reduced slightly, reducing consumption and boosting efficiency.
Direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion efficiency. It also reduces cold-start hydrocarbon emissions, compared to similar port-fuel-injected engines.
A higher compression ratio is possible because of a cooling effect as the injected fuel vaporizes in the combustion chamber. This reduces the likelihood of spark knock. The fuel injectors have been developed to withstand the greater heat and pressure inside the combustion chamber, and feature multiple outlets for enhanced injection control.
A cylinder head-mounted pump supplies fuel to the injectors at up to 2,900 psi (20 MPa). The pump is driven by a three-lobe cam on three-cylinder engines and a four-lobe cam on four-cylinder engines.
The engine-mounted fuel pump also uses dedicated control algorithms developed for the on/off control valve, enabling greater control of the valve needle at low speeds and low rpm, for lower noise and more consistent performance at lower speeds.
Math-modeled combustion system. An advanced combustion system on direct-injected variants combines a sculpted piston design with a comparatively small combustion chamber in the head to support the high-compression, mixture motion parameters enabled by central direct injection. Compression ratios vary among the Ecotec variants, but are as high as 12.5:1 on some engines, which enables greater specific output.
The pistons feature unique sculpted topography optimized via extensive analysis to direct the fuel spray precisely for a more complete combustion. The contours of the piston heads are machined to ensure dimensional accuracy—essential for precise control of mixture motion and the compression ratio.
General Motors employed one-dimensional and three-dimensional math-based models to refine the parameters of the combustion system design. The modeling helped determine the optimal 6-degree injector angle, as well as the shape of the chamber itself and the complementing piston dish, which is shaped to help direct the fuel spray for a more complete burn of the mixture.
Three-dimensional analysis also helped determine the optimal shape and length of the intake ports in the cylinder head, which feature a high-tumble design that promotes a more homogeneous mixture in the chamber.
Turbocharger system. Leveraging the design advantages of the integrated cylinder head/exhaust manifold, the turbocharger is more closely coupled to the engine, for quicker response that greatly reduces the lag that accompanies some turbo systems.
The system uses a comparatively small, low-inertia turbocharger (water-cooled) engineered to provide strong power at low rpm and immediate-feeling throttle response. It’s a single-stage, single-scroll unit used with an intercooler and pressure-activated wastegate. The diameter of the turbine wheel is only 35 mm, while the low-hiss compressor measures only 40 mm in diameter—an optimal combination that helps the engine deliver 90% of maximum torque at only 1,500 rpm for the 1.4L variant.
The turbo feeds the engine through high-tumble intake ports, which facilitate early combustion phasing, a short burn duration and good combustion stability. That means there is less need for spark retard at maximum boost pressure to avoid detonation, which can reduce performance.
|Among the testing procedures for the new engines was running on a tilt stand—a hydraulically actuated dynamometer that tilts the engine during operation to simulate driving on steep grades or high-speed cornering, which helps ensure the oiling system maintains full pressure during extreme driving conditions.|
Variable intake system. A two-stage variable intake manifold is used on some naturally aspirated variants to further enhance fuel economy and performance. At engine speeds below 5,000 rpm (at full load) inlet air passes through intake tracts that increase torque. At speeds greater than 5,000 rpm, a butterfly valve within the lightweight composite intake manifold opens to create a shorter intake path, enabling the engine to produce maximum horsepower.
This two-stage manifold helps the engine produce approximately 90% of peak torque from 2,200 rpm to 6,000 rpm.
Refinement. The all-new Ecotec engines have a quiet component set that contributes to smoothness and quietness, including:
Engine block and bedplate: The new Ecotec architecture’s refinement is rooted in its all-aluminum cylinder block, which is acoustically designed to reduce airborne and structure-borne operating noise. The structure is so good at quelling noise and vibration, the need to mask the transfer of engine noise with in-car sound insulation and other attenuation components is significantly reduced, which helps reduce the vehicle’s weight.
A bedplate provides stiffness to the bottom of the cylinder block and incorporates the main bearing caps—components used to secure the crankshaft within the block. Iron inserts cast into the bedplate enhance the structure at the main bearings, for greater smoothness and quietness. The insert material ensures close main bearing tolerances over a wide range of engine operating temperatures, for quieter engine lower-end noise.
Forged crankshaft: In turbocharged applications, a forged steel crankshaft is used to support the greater combustion pressures of forced induction with excellent durability, as well as enhance refinement with vibration-resistant performance—particularly at mid- and high-rpm levels, when the engine is producing maximum boost. The crankshaft is used with main bearings featuring tight tolerances that also contribute to good sound quality.
Oil jets: Piston-cooling oil jets not only enhance performance and durability, they provide an extra layer of oil on the cylinder walls and piston wristpins at start-up, which dampens noise emanating from the pistons.
Aluminum oil pan with a steel sump: A two-piece oil pan is composed of a structural, die-cast aluminum upper section, where it attaches to the cylinder block. The lower section features a coated, stamped steel sump—a design that helps reduce engine noise, because the steel section dampens noise better than an all-aluminum pan.
In-pan oil pump assembly and balance shaft: Mounting the oil pump assembly inside the oil pan reduces noise from the front cover area – an aluminum-intensive area that transmits noise – and minimizes the potential for pump cavitation noise.
On three-cylinder variants, a balance shaft is used to achieve four-cylinder-like sound and vibration qualities. It is mounted inside the oil pan and operates with the oil pump.
Inverted-tooth camshaft drive chain: The camshaft drive chain is optimized for low sound levels through an inverted-tooth design, which is significantly quieter than a roller-type chain. As its name implies, an inverted-tooth chain has teeth on its links—two-pin rolling pivot joints—that essentially wrap around the gear sprocket to take up virtually all the tension. This allows for smoother meshing of the chain links to the sprocket teeth, the cause of most noise in chain drive systems. The chain-to-sprocket tooth impact is greatly reduced with the inverted-tooth design (also known as a silent chain drive), substantially reducing noise and enhancing durability.
Camshaft drive system: In addition to the inverted-tooth camshaft drive chain, the entire chain-drive architecture, including its tensioning, wrap and guides, is designed for reduced overall noise radiation and the elimination of many perceived abnormal sounds. The tensioner is designed to never require adjustment, ensuring optimal chain tension and low noise performance for the life of the engine.
Structural camshaft and engine front covers: As a cast-aluminum part mounted on the very top of the engine assembly, the camshaft cover can be a significant source of noise. That’s not the case with the new Ecotec family, thanks to a structural cover design that mounts directly to the engine to enhance its overall stiffness—an attribute that helps push the engine’s sound frequency above 2,000 hertz. This frequency is attenuated easily with the acoustic treatment of the top engine cover, providing a lower overall radiated engine noise level as well as sound quality that is pleasing to the ear.
Similar to the structural camshaft cover, the front cover, which covers both the camshaft drive system and balancer drive systems, was designed with ribbing and other features to provide a stiffer, more rigid and quieter cover that contributes to lower engine noise.
Front-end accessory drive: The front-end accessory drive features an overriding alternator coupler to remove the effect of crankshaft oscillations. Along with refinement benefits, it also allows a reduction in tensioning force to reduce friction levels and improve efficiency.
Isolated fuel rail and fuel injectors: To reduce the noise associated with the high-pressure fuel system of direct injections, the injectors are suspended and the fuel rail is attached to the cylinder head with rubber-isolated, compression-limiting mounting provisions. This ensures there is no metal-to-metal contact and prevents the transmission from pulsing energy through the engine structure. The fuel pump and fuel line are also acoustically optimized.
Quieter turbo system: On turbocharged variants, the design of the turbocharger compressor reduces the characteristic whistle or hiss sound associated with turbo systems. Passengers feel the application of power as the turbocharger produces boost, but without the typical sound associated with it.