HOLDEN has added a gutsier 1.8, more engine and model choices, and a new convertible known as the TwinTop, as part of its facelifted AH Astra MY7.5 (Series II) range.

You will need to look hard to spot the changes though, which are limited to a redesigned front bumper and air-intake, a new grille, chrome headlight surrounds and new-style alloy wheels on the CDX and CDTi turbo-diesel, while higher-grade trim materials are now used inside.

Addressing lacklustre performance criticisms, the volume-selling CD and CDX three and five-door hatchback and wagon models gain an upgraded 1.8-litre ECOTEC twin-cam four-cylinder engine dubbed XER.

On more expensive 95 RON PULP premium-unleaded petrol, it now produces 103kW of power at 6300rpm, compared to the outgoing Astra 1.8’s 92kW (90kW on standard 91 RON unleaded) at 5600rpm.

This now puts the Astra’s 1.8 in sight of the 2.0-litre units found in the Mazda3 (108kW), Ford Focus (107kW) and Hyundai Elantra (105kW), lineball with the Civic 1.8 sedan and better than the 94kW Nissan Tiida 1.8, 93kW Corolla 1.8 and 92kW Subaru Impreza 2.0i – although both of the latter are on their last legs in Australia.

On the torque front, the figures rise to 175Nm at 3800rpm on five-speed manual XER cars, and 170Nm at 3800rpm on four-speed automatic XER models.

The latter is the same figure as the old 1.8 on PULP, but Holden says that more torque is available through a wider rev range, for improved driveability – 90 per cent from 2200rpm to 6200rpm, in fact.

However, Holden was unable to provide us with the XER engines’ standard-unleaded power and torque outputs, although it says extensive calibrations have been carried out so they can do say without any problems.

For the record, barring the Corolla, all of the aforementioned rivals have higher maximum torque figures (the Civic’s 174Nm is on 91 RON fuel).

The Astra 1.8’s fuel consumption and carbon dioxide emissions have fallen, by 0.4 litres per 100km and nine "or" 10 grams per kilometre respectively.

All manual XER cars return an ADR81/01 combined average fuel consumption figure of 7.4L/100km, rising to 7.8L/100km on the automatic vehicles and 7.9L/100km if we are talking about the auto wagon.

The Hungarian-built XER’s increased efficiency over the old 1.8 is partly due to the adoption of two continuously adjustable camshafts that are designed to optimise the cylinder’s charge cycle. It is also lighter and yet structurally stronger.

Meanwhile, Holden added a non turbo-charged SRi three and five-door hatchback (but not wagon, sadly), which also powers the new TwinTop, back in January, but waited until now to launch the vehicles to the Australian media.

It is an all-new, 2.2-litre twin-cam direct-injection petrol ECOTEC four-cylinder engine, delivering 110kW at 5600rpm and 210Nm at 4000rpm on PULP.

The high-performance, 147kW/262Nm 2.0-litre SRi Turbo coupe continues.

The 2.2-litre’s variable high-pressure direct fuel-injection technology enhances efficiency, according to Holden.

It also features all-aluminium construction, four valves per cylinder, variable intake control, a high compression ratio of 12.1:1 and, along with the 1.8 XER engine, Euro IV emissions compatability.

Buyers can ally the 2.2-litre models to a six-speed manual or four-speed automatic gearbox.

To test durability, powertrain cooling, heater/ventilation and air-conditioning performance and exhaust temperature functionality, Astra 2.2-litre engine prototypes underwent testing at Holden’s proving ground, as well as around Australia. Changes include revised auto shift points and reduced engine knock when running on 91 RON fuel.

ESP stability control is standard on all 2.2-litre models, along with anti-lock brakes with Brake Assist and four-wheel disc brakes.

Holden expects to maintain Astra sales at the 20,000-unit level it achieved in 2006.

As far as the CD and CDX cars are concerned, there are no price rises compared to their predecessors.

Nevertheless, GM Holden CEO Denny Mooney has accepted the fact that the Astra will not be able to achieve the 25,000-plus annual volumes of its TS predecessor.

"Here’s the deal with Astra – we are having a really hard time with the Euro (currency) right now," Mr Mooney told GoAuto.

"There’s two segments – Viva let’s us get below the $20,000 segment, and there’s no way we could get there with Astra.

"There is a big hunk of (sales) volume, and we’re challenged with the Astra to do historic volumes because of the strength of the Euro.

"It is very difficult with the exchange rates to get product out of Europe and hit those price points where the volume is.

Mr Mooney is also still supportive of the Astra diesel, despite disappointing sales so far.

"Markets where there are no artificial incentives – like tax breaks, lower-priced diesel fuel – you don’t see diesel sell... anywhere in the world.

"They sell more like a niche, unless it’s commercial stuff like trucks."

Still, Mr Mooney says that Holden will not lobby the government to lower diesel fuel excise.

"We talk to the government, and they say that they do not have a whole lot of reason to incentivise diesel – that is not where they want to put their money."

So will Holden persevere with the Astra diesel?

"I think so," Mr Mooney says. "As people get more and more educated about diesels and how clean they are, then (diesel sales) will grow."

Astra TwinTop

HOLDEN’S new AH TwinTop replaces the long running, and highly successful, TS Astra Convertible.

Like its ragtop predecessor, the TwinTop is a four-seater, but uses a retractable hardtop in the manner of the Peugeot 307 CC, Renault Megane CC and upcoming Ford Focus CC.

The TwinTop also replaces the unloved Tigra, which failed to make a dent in Australia due to a lack of an automatic gearbox option.

Unlike its French rivals, the Astra TwinTop uses a three-part roof mechanism.

Employing five electric motors, eight hydraulic cylinders and 14 joints, it is electronically operated, folds in 26 seconds at a touch of a button, and can be remotely done so via the key fob.

The roof can be raised and lowered even when the vehicle is in motion – up to 30km/h.

The boot volume roof-up is 440 litres, plummeting to just 205 litres with the roof in place. To better access luggage while the roof is down, an easy-load function raises the folded roof up by 25cm.

An interlocking blind process inside the boot stops the roof being lowered onto and crushing valuables already in situ inside.

The roof manufacturer is CTS Car Top Systems, the same Mercedes-Benz uses for its SLK and SL models.

Structurally, Opel in Germany beefed up the Astra Coupe base by reinforcing the A-pillars, side sills and floor, and then added a solid cross-member between in the floor at the B-pillars, implementing high-strength B-pillars and introducing further sill protection for side impact situations.

In rollover scenarios, high strength hydroformed steel tubes in the A-pillars have been devised, along with a rollover protection system that has been incorporated into the rear headrests.

Other safety features include ESP stability control, traction control, anti-lock brakes with Brake Assist, dual front and thorax/pelvis side airbags, and anti-whiplash active front head restraints.

All of the above means that the Astra TwinTop, while some 30 per cent stronger than the TS Astra Convertible, weighs almost 300kg more than the AH Astra SRi Coupe that it is based on.

As mentioned earlier, the TwinTop uses the same 110kW/220Nm 2.2-litre direct-injection four-cylinder petrol engine as the SRi, mated to the same six-speed manual or four-speed automatic gearbox.