New Ecotec Engines Deliver More with Less Complexity

2014-03-19


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  • Modular architecture reduces manufacturing complexity to enhance portfolio flexibility
  • Aluminum block and aluminum integrated head/exhaust manifold are light, enhancing vehicle performance and efficiency
  • Advanced technologies including turbocharging, central direct injection and variable valve timing support higher performance with great efficiency

DETROIT – General Motors’ new family of Ecotec small-displacement engines is the cornerstone of a powertrain strategy founded on downsized engines that deliver robust power with greater efficiency, segment-leading refinement and low CO2 emissions.

The new, modular architecture will eventually include 11 three- and four-cylinder variants ranging from 1.0L to 1.5L, including turbocharged versions, with power ratings ranging from 75 horsepower (56 kW) to 165 horsepower (123 kW), and torque ranging from 70 lb-ft (95 Nm) to 184 lb-ft (250 Nm). It is also designed to support hybrid propulsion systems and alternative fuels.

“We left nothing on the table when it came to designing the all-new Ecotec engine family,” said Tom Sutter, global chief engineer. “With the experience and expertise pooled from GM’s engineering centers in North America, Europe and Asia, these engines incorporate the performance, efficiency, durability and refinements customers in all global markets are seeking. The reduced complexity of the modular design also helps deliver those important attributes with strong value.”

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.

Numerous parts are shared between the initial production variants, which include a 1.0L turbocharged three-cylinder for the Opel ADAM and 1.4L turbo and 1.5L naturally aspirated engines for the 2015 next-generation Chevrolet Cruze for China.

GM will eventually build up to 2.5 million new Ecotec engines annually at five plants around the world, including Flint, Mich. (USA); Shenyang, China; Szentgotthárd, Hungary; Toluca, Mexico; and Changwon, South Korea.

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 precisely direct the fuel spray 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 details
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 percent 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.

Variable intake system details
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 percent of peak torque from 2,200 rpm to 6,000 rpm, giving it a strong, responsive feel in all driving conditions – and a confident feeling of power on demand.

Refinement details
Along with performance and efficiency, the new Ecotec engines deliver excellent refinement, with low vibration and noise levels. In fact, noise intensity is up to 50 percent quieter than Volkswagen’s EA211 1.4L four-cylinder and up to 25 percent quieter than Ford’s 1.0L turbo three-cylinder.

Engineers targeted every aspect of the architecture, reciprocating components, fuel system and engine management functions in the quest for world-class smoothness and quietness. It all starts with the all-aluminum architecture, which is acoustically designed to reduce airborne and structure-borne operating noise.  

Additional features that contribute to the engines’ refinement include:

  • The high-pressure fuel rail and injectors are isolated from the cylinder head. 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
  • The camshaft drive-chain is optimized for low sound levels through an inverted-tooth design. The entire chain architecture, including its tensioning, wrap and guides, is designed for reduced overall noise radiation and the elimination of any perceived abnormal sounds
  • The integration of a lower, stamped steel sump at the bottom of the aluminum oil pan also reduces noise
  • The front-end accessory drive features an overriding alternator coupler to remove the effect of crankshaft oscillations. In addition to refinement benefits, this also allows a reduction in tensioning force to reduce friction levels and improve efficiency
  • Acoustically optimized covers for the top and front of the engine
  • Crankshaft isolation with iron main bearing inserts
  • The design of the turbocharger compressor reduces the characteristic whistle or hiss sound associated with turbo systems.

Please see the separate Ecotec Refinement release for more details.

General Motors Co. (NYSE:GM, TSX: GMM) and its partners produce vehicles in 30 countries, and the company has leadership positions in the world's largest and fastest-growing automotive markets. GM, its subsidiaries and joint venture entities sell vehicles under the Chevrolet, Cadillac, Baojun, Buick, GMC, Holden, Isuzu, Jiefang, Opel, Vauxhall and Wuling brands. More information on the company and its subsidiaries, including OnStar, a global leader in vehicle safety, security and information services, can be found at http://www.gm.com.

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PRELIMINARY SPECIFICATIONS

Type:

inline 3- or 4-cylinder engines; naturally aspirated and turbocharged

Displacement range:

1.0L – 1.5L

Bore:

74 mm (all variants)

Stroke:

77.4 mm – 86.6 mm (depending on variant)

Block material:

cast aluminum

Crankshaft:

forged steel (turbocharged)
cast iron (naturally aspirated)

Cylinder head material:

cast aluminum

Valvetrain:

dual overhead camshafts, four valves per cylinder with continuously variable valve timing

Ignition system:

coil on plug

Firing order:

1-2-3 (3-cylinder)
1-3-4-2 (4-cylinder)

Fuel delivery:

central direct fuel injection or port fuel injection (depending on variant)

Compression ratio range:

10.0:1 (turbocharged) – 12.5:1 (naturally aspirated)

Horsepower range:

75-165 hp / 56-123 kW

Torque range:

70-184 lb-ft / 95-250 Nm

Recommended fuel:

regular unleaded

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