BMW Australia has introduced the final body variant of its highly successful current model 3 Series with the launch of its fourth-generation Convertible.

More than a quarter of a million units on from the first drop-top in 1986 (and following generations in 1993 and 2000), the E93 model is a significant step forward in replacing the previous fabric roof with a three-section steel roof that folds away into the top of the boot.

Two models are now available in Australia – the 2.5-litre 325i priced from $94,900 and the 3.0-litre twin-turbo 335i priced from $121,500 with a standard six-speed manual gearbox. A six-speed automatic transmission with manual sequential shift is an extra $2600.

Specifications and equipment levels are the same as the equivalent 3 Series Coupe models, which are about $13,000 cheaper.

The 325i features ABS, stability control, traction control, cruise control, fog lamps, rear parking sensors, rain sensors, auto air-conditioning, six CD-changer, auto-dipping mirror, onboard computer, multi-function steering wheel, leather upholstery, heated power front seats and Satellite Navigation.

As well as the more powerful engine, the 335i gets bigger 18-inch alloy wheels, active headlights, parking sensors front and rear, hi-fi speakers, front sports seats, electric lumbar adjustment on both sides and an upgraded SatNav system with a 22cm screen (versus 16cm in the 325i), TV and voice recognition.

BMW Australia expects that, initially at least, the more expensive 335i will account for the majority of sales (about 60 per cent).

Although the company will not project sales volumes because of supply constraints – the 335i waiting list already extends to the end of the year – it is confident of maintaining leadership in the luxury convertible market.

Built in Munich alongside the Coupe, the 325i is powered by the regular 2.5-litre aluminium-magnesium straight-six engine from the 3 Series range. This engine develops 160kW of power at 6500rpm and 250Nm of torque at between 2750 and 4000rpm, pushing the drop-top from rest to 100km/h in 7.8 seconds, or 8.4s with the auto.

Already seen in the Sedan and Coupe, the 3.0-litre twin-turbo petrol engine in the 335i cranks out 225kW at 5800rpm and some 400Nm across a huge rev-range of 1300 to 5000rpm. The 335i does the standing 100km/h run in 5.8 seconds (6.0s auto).

Combined fuel consumption for the 325i is 8.9L/100km (9.2 auto), and 9.9 for the 335i with either transmission.

There are no plans to offer four-cylinder or turbo-diesel engine variants in the Convertible.

Introducing a retractable hardtop has enabled the designers to include BMW’s signature “Hofmeister kick” in the C-pillar for the first time in a convertible, as well as making the side windows 30 per cent larger, to the benefit of rear seat passengers in particular.

The roof itself is made by roof specialist Edscha in Germany and retracts in 22 seconds, then closes in 23 seconds, activated by either a centre console button or the key remote control.

Boot space is naturally compromised with the roof stored away, reducing cargo volume from 350 litres to 210 litres, but a standard through-loading system into the back seat area provides added flexibility.

Access to the boot is aided by a function that allows the roof to half-open (in 10 seconds).

Torsional stiffness has been increased by 50 per cent with the roof down over the third-generation 3 Series Convertible, according to BMW.

Weight distribution is 50:50 and the centre of gravity is said to be slightly lower than the Coupe’s.

Safety features include pop-up rollover bars located behind the rear seats that activate in the event of a rollover when the roof is down, along with a strengthened A-pillar.

Dual front airbags are standard, along with head-thorax side airbags that are built into the front seat (as are the pre-tensioner seatbelts).

BMW’s controversial iDrive system has been further simplified. It has eight direct access “favourites” buttons on the dash that can be programmed for favourite radio stations, regularly dialled phone numbers or navigation destinations.

The standard leather upholstery employs innovative “SunReflective Technology” that claims to reflect infra-red radiation from direct sunlight, resulting in the seats being 20-degrees Celsius cooler than conventional leather.