THE quickest, most expensive and best-equipped Holden Astra five-door hatchback is now a turbo-diesel.

Priced from $29,990, Holden’s Belgian-built, Opel-sourced, small-car contender is pitched against upmarket Europeans like the Volkswagen Golf TDI, Peugeot 307 HDI and Citroen C4 HDI.

Holden is also hoping to score sales from the Japanese Toyota Prius and Honda Civic hybrid duo.

Only a single CDTi five-door hatchback model for available for now, although it comes in two distinct Euro IV emissions-compliant common-rail four-cylinder turbo-diesel engines according to which gearbox is specified.

Both are fitted with a Garret turbocharger and intercooler.

Holden’s diesel strategy is an unexpected one, as it is being presented as a sporty as well as an economical and green small-car alternative.

To this end the base six-speed manual CDTi boasts a 1.9-litre twin-cam 16-valve unit delivering a class-leading 110kW of power at 4000rpm and 320Nm of torque at 2000rpm.

In contrast the larger-engined Golf diesel alternative, the $32,490 2.0 TDI Comfortline, manages 103kW and 320Nm.

For an extra $1500, buyers can choose the $31,490 CDTi automatic, utilising an Aisin-supplied six-speed transmission and fitted with a sequential shift facility.

However, the automatic uses a single overhead camshaft, eight-valve version of the 1.9-litre engine, for 88kW at 3500rpm and 280Nm at 2000rpm.

It joins the Golf by offering a six-speed automatic gearbox in a diesel small car for under $40,000. Holden envisages the automatic/manual sales ratio to be 60/40.

Fuel consumption and carbon dioxide emissions are significantly lower in the manual though, recording an ADR 81/01 figure of 6.0 litres per 100km against the automatic’s 7.4L/100km, and 157 grams per kilometre versus 192g/km respectively.

Furthermore Holden says that two independently conducted economy drives have resulted the CDTi manual’s fuel consumption average falling to as low as 4.32L/100km. A 4.35L/100km average was achieved in some peak-hour driving conditions.

All Astra CDTi models, along with the new SRi petrol turbo released at the same time, introduce ESP stability control to the Astra range.

Also included are traction control, four-wheel disc and anti-lock brakes with electronic brake-force distribution, and dual front, side and curtain airbags.

The manual CDTi adds a Sports Chassis Pack, consisting of a 15mm lower ride height, firmer suspension, a quicker 14:1 steering ratio, and a ‘Sport’ switch that alters steering and throttle responses.

The regular Astra’s MacPherson strut-front and Torsion beam-rear otherwise remains much the same, as does the electro-hydraulic rack-and-pinion steering.

Fresh 16-inch alloys ride on 205/55 R16 tyres, backed up by an 80km/h-limited space-saver 16-inch steel spare.

Air-conditioning, a CD/MP3/radio audio with remote controls on the leather-trimmed steering wheel, cruise control, a trip computer, power windows, electric mirrors, and a remote-central locking are also included.

Holden commenced Astra diesel evaluation in Australia in 2003, and ran prototypes in that year’s, as well as the 2005, solar challenge race, totalling 6000km of testing.

Around 50,000km more were carried out for performance, fuel and air-conditioning testing, beyond the initial development Opel conducted for the Astra diesel globally.

Holden refuses to divulge CDTi sales expectations, which is understandable since its last diesel passenger car (the 1981 TE Gemini sedan) failed dismally.

However, Holden is quietly very confident, with dealer orders already surpassing initial expectations.

It also acknowledges that 65 per cent of Golf sales are TDI that small-car sales were up 19 per cent in 2005 over 2004, making up 215,300 of the total 980,000 new-vehicle volume that over 4700 diesels were sold last year compared to just 500 in 2003 and that 1950 diesels were sold in the first four months of this year.

If the Astra CDTi exceeds its secret targets, expect a wagon and three-door hatchback variants to follow.

Demographically 80 per cent of purchases will be private, skewed towards more male buyers, coupled, and with a dual annual income of $80,000-plus.

Holden is also pushing its one-time working-class hero Astra into new premium pricing territory.

The $27,990 base Golf 1.9 TDI manual undercuts the CDTi manual by $2000 (with a $1200 gap for the autos), although it cannot match the Astra’s performance and lacks ESP, cruise control, alloys and more.

Nevertheless, GM Holden chairman and managing director Denny Mooney is extremely cautious.

"I didn’t want to over-order diesels and then have too many cars out there ... because it is very easy to get over-enthusiastic," he admits.

"We’ll see how the market develops," Mr Mooney added.