Focused on meeting a growing customer demand for ‘downsized’ engines offering strong power with reduced fuel consumption and CO2 emissions, the new gasoline and diesel powertrains are being progressively introduced across the Opel product range.

New 1.6 SIDI Turbo gasoline engine

Compared to Opel’s previous 1.6-liter turbo engine, the new engine cuts CO₂ emissions and fuel consumption by 13%, while peak power and torque are increased by up to 30%.

Featuring Spark Ignition Direct Injection (SIDI), this all-new, four-cylinder gasoline engine comes in two configurations. The Eco Turbo version, delivering 125 kW (170 hp) and 280 N·m (207 lb-ft) peak torque, is focused on optimized fuel economy, high low-end torque and outstanding elasticity. The Performance Turbo, packing 147 kW (200 hp) and 300 N·m (221 lb-ft) peak torque, offers a high specific power output of 125 hp per liter.

Opel 1.6 SIDI Turbo. Click to enlarge.		1.6 SIDI Turbo torque-power curve. Click to enlarge.

At the heart of the new SIDI Turbo family is an all-new cylinder block able to withstand peak cylinder pressure of 130 bar. Cast iron was selected as the preferred material for the cylinder block in combination with an aluminum bedplate.

Opel’s SIDI Turbo is the only engine in its class to offer balance shafts. The two balance shafts are inserted in tunnels from the rear end of the cylinder block and are driven by an inverted-tooth chain. The exhaust side shaft features cast iron gears to reverse rotational direction of the exhaust shaft. The optional system offsets the vibrations inherent in the design of four-cylinder engines and thus helps to maximize comfort and reduce noise to a minimum.

Turbocharging for high low-end torque. Smaller displacement engines with high specific torque and boost levels require fast transient response, especially at low engine speeds, in order to be a valid replacement for larger displacement engines. Due to its specially designed turbines, the midsize gas engine’s turbocharger provides response that is usually generated by twin-scroll turbines on larger engines, Opel says.

The engine retains the proven concept of a turbine-integrated exhaust manifold. This design was chosen instead of a twin-scroll concept because of its packaging and manufacturing advantages. Although the turbocharger has identical interfaces, each variant of the new SIDI Turbo engine features a dedicated turbo aerodynamic.

The compressors are designed to deliver high low-end torque without generating noticeable aerodynamic sounds. Combined with low and high-pressure resonators, air-borne noises effects such as hiss, pulsation and blade-pass noise are almost completely suppressed. With additional aspects such as air handling, duct design and control strategies for let-off noise, the new engine benefits from an aggressive boost strategy without the typically associated turbo related acoustic degradation, the company says.

Compared to the predecessor engine, the new SIDI Turbo delivers an improvement in elasticity, for example, reducing the time for 80 km/h to 120 km/h fifth-gear acceleration by about 20%.

Central direct injection. Opel’s engineers selected a central direct-injection fuel system for optimum fuel efficiency and minimal emissions. The central location of spark plug and injector over the combustion chamber, and their orientation parallel to the crankshaft, forms a compact package with the capability to support homogeneous and stratified engine operation.

The valve train is operated by low-friction hydraulic roller finger followers and driven by a timing chain with a maintenance-free hydraulic tensioner. Acoustics are further improved by the inverted teeth of the cam drive chain. For mass reduction the midsize gasoline engine features a two-piece crankcase design, supported at the lower end by a die-cast aluminum bedplate.

Block and pistons. The cylinder block is manufactured using an innovative thin-wall casting method. This allows the integration of different functional features directly into the raw block and offers potential to reduce production time. The engine uses a broached press-fit between the cylinder block and the bedplate instead of dowels, in order to optimize the main bearing shape as well as its positional accuracy. The structural benefit derived from the combination of a forged steel crankshaft, optimized main bearing journal diameters, and iron main bearing cap inserts results in minimized noise and vibration at mid and high rpm.

Two different pistons have been designed for the Eco and Performance Turbo engines. Each has a dedicated top land including a small bowl. A cast iron ring carrier adapted to the high cylinder pressures is common to each piston. The PVD (Physical Vapor Deposition) coated first piston ring is an additional friction-reduction measure.

The new Cascada mid-size convertible is the first Opel model available with the new engine. Developed in the International Technical Development Center in Rüsselsheim, Germany, the turbo engine will soon expand the portfolio in further models.

New 1.6 CDTI diesel engine

Opel’s all-new, 1.6-liter turbo diesel delivers class-leading performance across all key engine parameters. It is launched in the Zafira Tourer and will be rolled out to replace the current 1.7-liter and lower powered 2.0-liter diesel engines in a wide range of Opel models, with even more powerful versions to come.

Delivering 100 kW (136 hp) and torque of 320 N·m (236 lb-ft), Opel’s first all-aluminum diesel engine offers power density of 85 hp per liter—unrivaled in its class, according to Opel.

Opel 1.6 CDTI. Click to enlarge.		1.6 CDTI torque-power curve. Click to enlarge.

Architecture. Opel engineers focused on getting an optimal balance between all the requirements for power, fuel economy, refinement (low noise, vibration and harshness), emissions, weight and affordability—priorities which can often conflict.

One of the many performance targets was the achievement of a best-in-class engine power-to-weight ratio, which dictated using aluminum, instead of conventional cast iron, for the cylinder block. This is a first for Opel diesel engines and, combined with an aluminum bedplate and cylinder head, saves more than 20 kilograms (44 lbs) in weight.

While aluminum is light, its use for a diesel engine block offers a greater challenge than cast iron in terms of ensuring strength and a low operating noise. To withstand peak cylinder pressures of 180 bar and reduce radiated engine noise, the block is produced from high-grade aluminum in a precise, multiple-core casting process.

With the aid of FEM analysis, material strength is concentrated where it is needed most. The high pressure, die-cast aluminum bedplate, with cast iron inserts to carry the crankshaft, also provides cross-bracing to further increase block rigidity and reduce noise.

Dual, chain-driven overhead camshafts, including weight-saving hollow sections and lobes, operate four valves per cylinder with low-friction, hydraulic roller finger followers. The pistons, in aluminum for reduced reciprocating mass, feature a concave, shallow-bowl profile to facilitate efficient combustion and are cooled by under-skirt oil spraying. The crankshaft, with four counterweights to minimize mass, and the con-rods are in forged steel.

A near square bore/stroke ratio of 79.7/80.1 mm was chosen as the best compromise for good engine breathing, excellent thermodynamic efficiency and efficient packaging. In the same way, a compression ratio of 16:1 was selected as a balanced compromise between requirements for strong power, low emissions and good cold starting performance.

Power density. Key to the engine’s performance is a high-pressure, common-rail fuel system allied to closed-loop combustion control and strong intake charging from a variable geometry turbocharger (VGT).

Injector nozzle pressures of 2,000 bar—a 25% increase over previous engines—enable the delivery of up to 10 injection pulses per cylinder cycle. This enables high power, improved fuel atomization and efficient mixing with the air intake charge. Multiple injections also make the combustion process clean, smooth and quiet. All internal components in the precision-made injectors are treated with an extremely hard, diamond-like coating to resist the stresses produced by a high power density.

Closed-loop combustion control enables instantaneous fine-tuning of the fuel injection. High speed, piezo-resistive cylinder pressure sensors are integrated in the glow-plugs to acquire real-time data on combustion quality. This allows a faster and more precise adjustment of the fueling than map-based systems.

A lightweight, aluminum fuel pump with a suction control valve allows delivery of the exact amount of fuel requested, avoiding energy waste that is normally necessary in regulating fuel pressure. It is particularly effective in low engine load conditions, such as during city driving, Opel says.

On the intake side, the inlet ports are carefully designed for optimal performance by ensuring a good swirl pattern and air mass flow with a low pressure drop. In this respect, the 1.6 CDTI is up to 4% more efficient than previous generation Opel engines, and up to 10% better than competitor engines, according to the company.

The VGT is able to operate at a high peak boost pressure of 1.7 bar and provides a dense intake charge in combination with air-to-air intercooling. And with a variable aspect ratio at the turbine, it gives the driver a strong, smooth and rapid throttle response at all engine speeds. For durability, it is water-cooled.

The VGT and the exhaust gas recirculation (EGR) function were developed as a single, complete system. Different turbocharger sizes and EGR circuit design combinations were evaluated during the optimization process. The key goal was to balance low-end torque and peak power requirements with an adequate EGR capability. As a result, a compact EGR module has been designed, with a high cooling efficiency of up to 92% and a low pressure drop.

Fuel consumption. Compared to the current 2.0 CDTI engine with similar power, the new 1.6 CDTI offers a 10% reduction in fuel consumption and CO₂ emissions. In the Zafira Tourer, the engine delivers combined cycle fuel consumption of 4.1 l/100 km (57.4 mpg US) and 109 g/km CO₂. In smaller vehicle applications, the engine is expected to enable sub-4.0 l/100 km (58.8 mpg US) fuel consumption and CO₂ emissions near or below 100 g/km.

In addition to an optimized combustion process, the low internal friction of mechanical components is another key enabler of good fuel economy. Applying an industry standard measure for friction, Friction Mean Effective Pressure (FMEP), Opel research shows that the 1.6 CDTI has the lowest friction rating for all diesel engines over a speed range from 1,750 to 2,750 rpm, typically used in everyday driving.

In terms of Brake Specific Fuel Consumption (BSFC), the 1.6 CDTI also returned the best figures in testing at part-load/2,000 rpm.

Every engine component and function is optimized for its contribution to fuel economy, no matter how small. Examples of some of the detailed measures taken include:

• Switchable water-pump. An electromagnetic clutch decouples the water pump pulley during engine warm-up, enabling normal operating temperature to be reached more quickly while reducing engine load and fuel consumption.

• Variable displacement oil pump. This helps optimize fuel consumption by operating at high or low pressure to vary the oil supply according to engine load requirements.

• Electrically-controlled piston cooling jets. A solenoid valve manages the operation of the oil jets according to a defined logic. In conjunction with the oil pump control strategy, this further reduces power drain from the lubrication system.

• New Diesel Particulate Filter (DPF) regeneration algorithm. This more accurate algorithm allows significant gains in mileage between DPF regenerations, without any risk of soot overloading. The frequency of regenerations is reduced and fuel economy is improved.

NVH. Advanced CAE simulation tools and several optimization loops were used to assess the noise character of each component and sub-system before the first prototype engine was even built. Refinements were then validated by testing in a semi-anechoic chamber across a range of hot and cold engine running temperatures. The development team focused on overall engine noise characteristics and single component optimization.

Contributors to the engine’s running refinement include:

• Optimized combustion process with multiple fuel injection pulses.

• Radiated noise minimization in engine block design, including use of a die-cast aluminum bedplate instead of separate caps.

• Glass-fiber reinforced plastic (GRP) cam cover, fully decoupled from the engine to reduce noise and vibration, while also saving weight compared to aluminum.

• Composite intake manifold encapsulated in acoustic padding and an external plastic shield, significantly reducing noise emissions.

• Mechanical crankshaft isolator reducing radiated noise and torsional vibrations in the accessory drive system (water-pump, air conditioning compressor and alternator).

• Scissor gear from the crankshaft for the timing drive system incorporating tooth profiles ground with a Low Noise Shifting (LNS) process for optimal noise reduction.

• Dual-mass flywheel and automatic accessory drive tensioning for greater running refinement.

• Precise balancing to reduce resonance at the compressor inlet and outlet of the VGT turbocharger.

Euro 6 with SCR. The introduction of Opel’s BlueInjection selective catalytic reduction (SCR) system assures compliance with Euro 6 emissions standards (effective September 2015).

The BlueInjection SCR system is precisely managed by the engine control unit through a dedicated temperature sensor and two NO_x sensors.

The required AdBlue urea solution, available at filling stations and Opel dealerships, is stored in a tank, which can be topped up as required via a nozzle alongside the car’s fuel filler cap.

In-house engine control unit. More than 150 patented diesel control functions are deployed by the 1.6 CDTI’s engine control unit, developed in-house by General Motors. This advanced ECU, engineered in Italy, Germany and the United States, will be used in all future four-cylinder diesel engines.

It has enabled the integration of the 1.6 CDTI and its software logics throughout the entire design and development process, ensuring optimization of the whole system and the achievement of best-in-class performance levels.

The software architecture is based on modularity with standardized interfaces. The number of sensors required is also reduced by the extensive use of models. GM owns the ECU’s architectural definition, the software and its algorithms, which speeds up development time, increases reliability, and reduces supplier dependence and system cost.

The ECU incorporates a single-core main microprocessor with 4 MB Flash, 256 KB RAM and a 256 MHz clock. The many engine functions it controls include:

• Closed loop combustion control system with in-cylinder pressure sensors
• Integrated glow plug drivers
• Common rail fuel management with high/low voltage solenoid injectors capability
• Variable, up to 10, injection pulses per cylinder cycle
• Fuel delivery compensation algorithms
• VGT and waste-gate
• Advanced EGR functions, high/low pressure
• Variable swirl actuation
• DPF physical model and regenerations
• NO_x aftertreatment: selective catalytic reduction (BlueInjection SCR) and lean NO_x trap (LNT)
• Smart cooling and lubrication
• Engine Start/Stop
• Improved diagnostics for more efficient serviceability

New transmissions

In line with the roll-out of its new engine portfolio, Opel is introducing from now through 2016 a range of enhanced manual and automatic transmissions. The first phase in Opel’s transmissions transformation is already underway with the introduction of next generation manual gearboxes. These five and six-speed manuals match their best-in-class competition for fast, smooth shifting. Additional highlights in the roll-out include an all-new six-speed manual gearbox, a manual automated transmission, and in the longer term an all-new eight-speed automatic.

Opel has invested more than €50 million (US$65 million) at its European facilities in improving its current five and six-speed manual transmissions. Numerous revisions to the transmission internals and shifter mechanisms, as well as their in-vehicle integration, have enabled a significantly reduced shift travel with very low shift lever forces—typically less than required to push in a small drawer at home.

For a smoother engagement, all gearboxes have gears with wider, partly asymmetrically-cut dog teeth. Triple-cone synchronizers for first and second gear have also been re-profiled for five-speed gearboxes, and enlarged by 10% for six-speed units. For third/fourth gear, there are now double cone synchronizers on five-speed gearboxes and triple cones for six-speed units. Reverse gear is synchronized.

Shift-quality is improved by the introduction of a more direct external linkage with revised cabling to minimize friction. For the driver, this has reduced gear shift travel and also delivered a more connected feel, allowing the shift lever to snap easily into position with a minimum of effort.

An additional comfort feature is the installation of an internal vibration absorber to eliminate any vibration in the shift lever. The use of low viscosity oil also improves shifting comfort, particularly in cold-start conditions, as well as contributing to the powertrain’s reduced fuel consumption and CO₂ emissions.

New 6-speed. More than 1 million kilometers (620,000 miles) of validation testing in cold and hot weather conditions was carried out during the development of the new, next generation manual gearboxes. The lessons learned have also been used in the design of an all-new six-speed gearbox.

It will be introduced in small and sub-compact vehicles with engines rated up to a 235 N·m (173 lb-ft) maximum torque. In each application, the new gearbox will be integrated with an available choice of 12 sets of gear ratios and seven final drives.

While the new gearbox incorporates all the improved shift quality measures introduced for the next generation units, its all-new design has enabled a dry weight of 37 kilograms (82 lbs), which is up to 15% lighter.

New automated manual. Opel’s new automated manual transmission utilizes an electro-hydraulic clutch actuator to eliminate the need for a clutch pedal. Instead of using two electric motors for gear selection and shifting, it now features an all hydraulic operation to give a substantially smoother gear change quality.

New control modes between the engine and transmission control units contribute substantially to performance improvement. Other new features, applicable for both automatic and manual modes, include power launch for optimized take-offs, start/stop functionality and vehicle creep movement.

The new automated manual transmission is developed from Opel’s next generation five-speed manual gearbox, employing its high precision shift system. The gearshift lever is used to select Drive, Reverse or Neutral mode in full automatic operation, and can be moved across its gate for sequential style, manual gear shifting. This new gearbox for primarily small cars supports engines with up to 190 N·m (140 lb-ft) of torque.

New 8-speed. In the longer term, a new eight-speed automatic transmission will add a high-end transmission to the portfolio. Compared to a six-speed operation, the wider gear spread enables an average improvement in fuel economy of more than 3%, and more responsive performance.

With a maximum power rating of 500 N·m (369 lb-ft), the transmission features a control logic giving fast shift response times. It also offers a future capability for Start/Stop functionality.

Other contributors to its efficiency include smart design packaging, which has reduced its weight and length compared to the six-speed unit, an improved oil pump operation and lower cooling requirements.

Before the eight-speed gearbox is introduced, a next generation six-speed automatic transmission will also make its debut in compact and midsize vehicles. This offers active steering wheel controls while in Drive and enhanced engine braking without manual downshifting—as well as the current driver-adaptive, fuzzy logic and choice of eco, sport or manual driving modes.

Futures. Looking further ahead, Opel is also working on a dual-clutch transmission (DCT) as well as 9- and 10-speed torque converter-based automatics.

These will be introduced as part of a coordinated program in which each Opel vehicle and its sub-systems, including the transmission, have clearly defined targets in order to meet overall EU CO₂ fleet requirements of 130 g/km in 2015 and beyond. While increased engine efficiency will be the main contributor, transmission systems account for 7–12% of powertrain losses when converting fuel energy into motive power, so they also have an important role to play in helping to reduce emissions.