|The 1.3-liter diesel CDTI for the Astra. Click to enlarge.|
Opel introduced the new Astra at the Frankfurt Motor Show (IAA) earlier this month. (Earlier post.) The new Astra is launching with a complete line-up of eight gasoline and diesel engines ranging from 70 kW/95 hp to 132 kW/180 hp. The new Astra has grown slightly to provide a roomier interior and, at the same time, it has benefited from engineering enhancements that allow it to improve fuel efficiency and performance.
The Astra’s line-up of powertrains with manual transmission cuts fuel consumption and CO2 emissions overall by more than 12% compared with the current generation. The average fuel consumption of the four diesel engines ranging from 70 kW/95 hp to 118 kW/160 hp, which are expected to represent almost half of the new Astra cars sold in Europe at launch, is 4.6 L/100 km (51 mpg US).
The CDTI turbo diesel line-up includes 1.3, 1.7 and 2.0-liter units, each featuring common-rail with multiple fuel injection equipped with particulate filters. The top-of-the-line 2.0 CDTI with 118 kW/160 hp requires 4.9 L/100 km (48 mpg US) on average and emits no more than 129 g/km CO2. A new diesel 1.3 CDTI ecoFLEX generation with CO2 emissions of 109 g/km and an average fuel consumption of 4.2 L/100 km (56 mpg US) will be added to the range in spring 2010.
The gasoline range comprises naturally-aspirated and turbocharged 1.4 and 1.6-liter engines, giving a power bandwidth from 74 kW/100 hp to 132 kW/180 hp. The average fuel consumption of the four gasoline engine line-up is 6.1 L/100 km (38.6 mpg US).
The 74 kW/100 hp entry-level version in the gasoline line-up consumes 5.5 L/100 km (43 mpg US)and does not emit more than 129 g/km CO2. This makes it the most fuel-efficient gasoline compact on the market, according to Opel. Continuing Opel’s strategy of downsizing, a new 103 kW/140hp 1.4 Turbo gasoline engine replaces the current 1.8 liter variant, improving fuel efficiency by nearly 18%.
Four naturally aspirated or turbocharged 1.4 and 1.6 gasoline engines. Four naturally-aspirated and turbocharged 1.4 and 1.6-liter engines compose a line-up of 74 kW/100 hp to 132 kW/180 hp.
All engines are transversely-mounted four-cylinder units with aluminum cylinder heads carrying dual overhead camshafts that operate four valves per cylinder. Cylinder blocks are in cast iron for strength and reduced noise resonance, with a hollow frame design for minimized weight. A die cast, structural aluminum oil pan adds further stiffness and provides further noise reduction.
Continuously variable valve timing is featured in all engines on both inlet and exhaust sides, except the 1.6-liter turbo. The camshafts have hydraulically operated vane-type phasers which vary the angle of each camshaft relative to the crankshaft by up to 60 degrees on the inlet side and 45 degrees on the exhaust side.
Cam phasing allows the engine control module to adjust the timing of the opening and closing of the valves according to varying conditions, such as engine speed and engine load. Among the benefits are a broader spread of torque, higher maximum power and improved fuel consumption. Cam phasing is also an effective tool for controlling exhaust emissions, managing valve overlap at optimum levels to eliminate the need for a separate exhaust gas recirculation (EGR) system. The coolant thermostat and the oil pump are electronically controlled to improve engine heat up.
The entry-level 1.4-liter, naturally-aspirated engine develops 74kW/100 hp at 6000 rpm, with a specific power output of 52.8 kW/71.4 hp per liter. It focuses on excellent fuel economy and returns 5.5 L/100 km over the combined cycle, the best figure for a gasoline engine in the compact segment.
The camshafts are chain-driven for maintenance-free operation and automatic hydraulic lash adjustment. Further refinements include the use of hollow camshafts, which reduce weight and lower reciprocating mass, and a torsional vibration damper that improves running refinement. The fuel injection system also features port deactivation under part load for improved exhaust gas recirculation, giving lower emissions and improved fuel consumption.
The 1.6-liter naturally-aspirated engine develops 85 kW/115 hp at 6,000 rpm and has an even higher specific power output (72.5 hp) per liter than its 1.4-liter, naturally-aspirated cousin. Maximum torque of 155 N·m (114 lb-ft) is generated at 4,000 rpm, with more than 90% of this value available from 3,000 rpm. The combined cycle fuel consumption is 6.3 L/100 km (37.3 mpg US).
A two-stage variable intake manifold is fitted to this engine. For increased torque at engine speeds below 4,000 rpm, the fuel/air intake charge passes through 620 mm long inlet tracts. Above 4,000 rpm, the engine management system transmits a signal to channel the air along shorter 288 mm tracts, which has the effect of increasing top-end engine power.
The engine’s cylinder barrels are laser-etched for an extremely smooth finish. This results in minimal piston friction and wear characteristics, while also benefiting oil and fuel consumption. Under-skirt piston oil cooling is a further addition.
The new, downsized 103 kW/140 hp 1.4-liter turbo engine that replaces a naturally-aspirated 1.8 engine of similar output is focused on strong performance with high elasticity, enabled by 200 N·m (148 lb-ft) of torque available between 1,850 and 4,900 rpm. Compared to the 140 hp/175 N·m 1.8 engine from the current range it replaces, it delivers 14% more torque with fuel consumption of 5.9 L/100km (39.9 mpg US)—an improvement of nearly 18%. These power characteristics translate to a zero to 100 km/h acceleration in 9.7 seconds, and a transition from 80 to 120 km/h in fifth gear in 13.3 seconds.
The water-cooled turbocharger, spinning at up to 240,000 rpm, is integrated into the exhaust manifold close to the engine for a fast throttle response. Air-to-air inter-cooling increases the intake charge density.
The adoption of a reinforced crankshaft, reinforced pistons and con-rods allows the use of relatively high 9.5:1 compression ratio, despite higher stresses and loads. Under-skirt piston oil cooling jets, an oil cooler and exhaust valves filled with sodium are further features ensuring durability under higher internal temperatures.
The most powerful gasoline engine is the 1.6-liter turbocharged which exceeds 110 hp per liter in delivering a maximum power of 132 kW/180 hp. Developed for customers focusing on dynamic driving characteristics, it is the most powerful production engine in its displacement class.
Great performance is matched by an impressively wide plateau of torque, with 230 N·m (170 lb-ft) available all the way from 2,200 rpm to 5,400 rpm. For quick and safe overtaking maneuvers, an overboost function can briefly unleash even more torque, raising it to 266 Nm for up to five seconds.
With this engine, the new Astra achieves zero to 100 km/h acceleration in 8.5 seconds, and makes the 80 to 120 km/h transition in fifth gear in 10.5 seconds.
Like the 1.6 naturally-aspirated engine, the cylinder barrels are laser-etched for minimal piston friction. To withstand higher operating temperatures, the exhaust valves are filled with sodium and under-skirt piston cooling with oil jets is used. A map-based thermostat control raises the coolant temperature at low engine speeds or under light loads to help reduce internal lubricant friction and improve fuel consumption.
Three diesel engines in four output variants require less than 5.0 liter/100 km. The CDTI turbo diesel line-up includes 1.3, 1.7 and 2.0-liter units—all common-rail with multiple fuel injection and standard particulate filter—which range in power from 70 kW/95 hp to 118 kW/160 hp. All benefited from the latest developments and refinements in engine management calibration, which allowed a 14.5% improvement in fuel efficiency across the range compared to the current Astra diesel line-up.
The four engines require less than 5.0 liter/100 km on average (47 mpg US)—with CO2 emissions that do not exceed 129 g/km even for the 118 kW/160 hp 2.0 CDTI. A first ecoFLEX generation powered by the 70 kW/95 hp 1.3 CDTI engine with CO2 emissions of 109 g/km and average fuel consumption of only 4.2 l/100 km will be added to the range in spring 2010.
All CDTI engines in the Astra are fitted with 16-valve, dual overhead camshafts, a weight-saving aluminum cylinder head, specially shaped intake ports for exceptional swirl and burn characteristics, oil-jet-cooled pistons, a dual-mass flywheel and a maintenance-free particulate filter. The main technical features include:
Common Rail, Multiple Fuel Injection. Operating at high pressures up to 1,800 bar (1,800 bar for the 1.7-liter; 1,600 bar for the 1.3- and 2.0-liter engines), this fuel delivery system ensures extremely fine atomization in the combustion chamber and enables up to five injection pulses per cycle to extract as much energy as possible from a given amount of fuel. This results in low fuel consumption and exhaust emissions, as well as reduced engine noise. Multiple injections help iron out the strong vibrations associated with compression ignition. For example, a pre-injection during the warm-up period reduces cold-start knock to a barely perceptible level.
Variable Geometry Turbocharger (VGT). The pitch of the vanes on the turbine wheel is continuously varied according to engine load and speed, giving an excellent throttle response, particularly during pick up from low speeds.
Improved Exhaust Gas Recirculation (EGR). The electronically-controlled EGR system has an additional cooling function. Electro-pneumatically operated bypass flaps controlled by the engine management system ensure that the exhaust gas reaches a temperature suitable for combustion on its way back into the cylinder. This contributes to increased power as well as reduced emissions.
The 70 kW/95 hp, 1.3-liter CDTI in the new Astra ecoFLEX offers fuel economy of just 4.2 l/100 km over the combined cycle and CO2 emissions of only 109 g/km, with strong torque of 190 N·m (140 lb-ft) between 1,750 and 3,250 rpm.
The 1.7-liter CDTI comes in two states of tune, providing 81 kW/110 hp and 260 N·m, or 92 kW/125 hp and 280 N·m of torque. Combined cycle fuel consumption in both cases is 4.7 L/100 km (50 mpg US).
The 2.0-liter CDTI which debuted in the Insignia packs 118 kW/160 hp with torque of 350 N·m (258 lb-ft) from just 1,750 rpm. With the overboost function, 380 N·m can be reached for up to 15 seconds, giving the driver extra power when needed. The result is zero to 100 km/h achieved in 9.0 seconds together with combined cycle fuel consumption of 4.9 L/100 km (48 mpg US).
Transmissions. Six-speed manual gearboxes offering a wide spread of ratios and a long, fuel-saving top gear are a standard fit across the range, with the exception of the 1.4/1.6-liter naturally-aspirated and the 1.3-liter turbo diesel engines which have five-speed gearboxes. Such five-speed, two-shaft units are preferred due to their advantages in efficiency and mass balance, optimizing fuel economy. All gearboxes feature triple cone synchronization in the first and second gears for easy engagement.
An all-new, six-speed automatic transmission with an ActiveSelect function is available as an option with all gasoline engines except the 1.4-liter naturally-aspirated unit which is manual only.
The on-axis design allows more compact packaging, resulting in enhanced crumple zone performance, increased interior space, and a lower hood line than with a conventional off-axis design. Instead of the transmission being folded around the end of a transversely-mounted engine, the gear sets are now on the same axis as the engine crankshaft centerline, which makes the entire powertrain unit much shorter fore-to-aft. Shifts are accomplished by applying and disengaging clutches simultaneously, which provides increased functionality and a more direct feel for the driver compared to freewheeling gear change mechanisms.
On the road, a wide selection of shift patterns is adapted to the styles and habits of the driver, anticipating when maximum acceleration or maximum efficiency is required. The electronic control also adapts to the prevailing road conditions, reducing gear shifting when climbing or descending and using engine braking assistance during down shifts.
ActiveSelect allows sequential driver gear selection via the shift lever. The driver also benefits from neutral gear disengagement at idle, which reduces vibration and contributes to improved fuel consumption.
Hydraulically-damped mountings for smoother operation. All powertrains are bolted in position via hydraulically-damped mountings that minimize vibration through the body structure. Adaptor plates enable the same four fixing points to be used for all applications, two on the front sub-frame and one on each longitudinal beam.
The fuel supply system uses an electric pump and filter mounted in the 56-liter fuel tank, which is located low under the rear seat for optimal weight distribution and crash impact protection.