2017 Holden Astra sedan prototype review

Holden's Lang Lang proving ground is littered with cars like this, all covered in swirly vinyl wraps and fitted with mix-matched parts designed to keep the real thing hidden from prying eyes when they venture outside its boundaries.

Generally they are also kept far away from us too, but not today. Holden has allowed a select group of motoring media inside its Lang Lang lair to sample prototype variants of its next small car contender, the Astra sedan, which is due to go on-sale here in a couple of months.

Like other imported models, Holden's crack team of engineers, led by Jeromy Tassone, has spent considerable effort in fine-tuning the base package of the Korean-sourced sedan to suit Australian roads and customer demands.

To highlight some of the lengths they go, and the results they achieve, Holden was keen to showcase the improvements it has made to the Astra sedan in terms of ride and handling and overall refinement.

Firstly, the four-door is closely related to the hatch that arrived here late last year but it isn't a direct sibling as it is effectively known as the Cruze in all of the other markets it is sold in, and will be sourced from Korea rather than Europe as Opel doesn't plan on developing a sedan variant but rather a wagon that is more popular in continental regions.

It uses the same basic small car platform, dubbed D2XX in General Motors' speak, but rides on a longer wheelbase and has a less sophisticated torsion beam rear suspension with the Watts linkage from the hatch.

It will be exclusively powered by the 110kW/ 240Nm 1.4-litre turbo charged four cylinder available in the lower-grade Astra R hatch with a choice of either a six-speed manual or automatic transmission driving the front wheels.

It will be offered in three trim levels - LS, LT and LTZ - that are positioned slightly cheaper and more comfort-oriented than their sportier hatch equivalents. While all three will feature six airbags and a rear-view camera, and the top-grade variants will have Holden's Eyesight safety suite with forward collision warning, blind spot alert and automated parking assistance, none have the option of automated emergency braking.

Before the final versions arrive in showrooms, the prototype models we're testing are called 65 percent integration vehicles. They are essentially mechanically relevant to the final production models, with elements that can still be fine-tuned while details such as the plastics used in the cabin don't have the same level of finish as those that will make it into showrooms.

The two cars at our disposal - one used for testing Holden's suspension, transmission and stability control tweaks and the other to validate local tuning for electronic systems such as the sat nav and audio system - were hand-built in Germany and shipped to Lang Lang over a year ago when the Australian test process began.

Today, we've also got a full production Astra R hatch as a reference point over a series of exercises within Lang Lang - a slalom on a dirt track designed to showcase the stability control intervention and a few circuits around a demanding ride and handling course to assess the suspension and steering improvements - as well as a road loop through the Gippsland hills that Tassone and his team regular use to test in more real-world conditions.

We've already driven the Cruze sedan in America earlier this year and was reasonably impressed with its packaging and the overall presentation of its interior, but it clearly didn't have the dynamic flavour that Holden wanted.

If anything, the prototypes showcase - once again - the impressive results achieved by Holden's engineering team. While Tassone claims the objective was to ensure the sedan has a more conservative bias towards comfort, rather than the sportier flavour of the hatch, he concedes there also needs to be a common dynamic thread between the two.

The outcome is that Holden may have achieved both. Compared to the hatch, which Holden took virtually unchanged from Europe, the 'ride and handling' sedan's steering is clearly lighter but feels a little more consistent across the ratio with a nice natural feel. The suspension feels more compliant over small, sharp bumps and also reacts better to bigger impacts, and while there is a little more body roll through the bends when driven enthusiastically it is predictable and stable and can be hustled harder than anyone will probably ever push it.

The dirt slalom run showcased how gently, but effectively, its electronic stability control intervened when driven on low-grip surfaces, as well as the benefits of its torque vectoring system which Holden also re-worked to suit local conditions. 

Out on the road, the 1.4-litre engine needed to be pushed hard to keep pace during some steep inclines but the automatic worked intuitively enough and responded positively to inputs, shifting down gears smoothly to maintain momentum.

All in all, it appears that Holden has done another cracking job by injecting some dynamic flavour into the Astra sedan in the areas that needed it most. 

But we'll reserve our judgement on where the Astra Sedan fits into the booming small car community until we get behind the wheel of one without swirly camouflage and a cloaked interior.

• For more information visit our Holden showroom