BMW (UK) expects entry-level four-cylinder models to account for the bulk of sales of its new 1 series convertible line.

The new model is the first compact BMW convertible to be launched in 30 years and has a fabric top, rather than a folding metal roof, as is now used on the latest, larger 3-series cabriolet.

Designer Kevin Rice, a Briton, said this allowed a more stylish design, was cheaper and easier to engineer and appealed to customers who prefer the traditional fabric roof.

The BMW drop-top is available in black, beige, or anthracite (posh black) with silver flecks and is a fully automatic, electro-hydraulically operated device on all models. It can be opened and closed at up to 31mph (about 50km/h). It fits beautifully, seals well and feels nice to the touch, inside or out.

BMW (UK) marketing director Uwe Ellinghaus said: “The time is ripe for BMW to introduce the 1 series convertible. The latest 3 series convertible is selling well within its slightly more premium target market, with its larger dimensions and retractable hard-top folding roof.

“This move allowed the scope for a compact, premium BMW car with a fabric roof to come to market.

“The 1 series is a performance-oriented product that is expected to appeal to the younger-than-normal BMW buyer.”

BMW UK initially expected to sell around 2,750 1 series convertible models in 2008. The 118i is likely to be the most popular model accounting for more than 40% of sales. The 120i (about 30%) and the 125i and 120d (both more than 10 per cent each) will be the next most popular variants. The high performance 135i with its niche positioning is expected to garner single digit per cent sales.

Insiders said early ordering patterns suggest the diesel share could go as high as 15-20%, however.

Though convertible buyers have not traditionally been big diesel fans, BMW reckons their better fuel economy and lower CO2 emissions will win more custom, in the wake of a UK budget that hiked CO2-related annual road tax and the amount of tax paid by company car drivers.

BMW expects to sell around 3,850 of the new cabriolets in a full year, and about the same number of the new coupe. The five-door hatchback that launched the 1-series here several years back sold 18,158 units last year (its peak was 22,000) while the new 3-door made 4,643 in 2007 and is expected to peak at 8,000 a year.

All 1-series convertibles have BMW’s EfficientDynamics technology with brake energy regeneration, intelligent alternator control and an absorbent glass matt battery to harness engine power that would normally have been lost during engine over-run or braking. The alternator only works when needed to reduce fuel consumption and improve performance.

All four-cylinder manual gearbox cars also have auto start-stop as standard. In urban traffic, when in neutral with the clutch pedal raised the engine automatically cuts out, thus eliminating emissions and any fuel consumption while static. When the traffic restarts, the clutch is depressed in order to select the gear to pull away, the engine fires  immediately.

An optimum gear shift indicator is also fitted on all manual-gearbox cars to inform the driver of the appropriate gear for the most economical driving; this, we found discourages the revving that all BMW engines seem to thrive on.

All models bar the range-topping twin-turbo 135i have electronic power steering.which operates on an ‘on-demand’ basis, reducing the engine output normally needed to power the steering hydraulics. This results in a 90% energy saving compared with a conventional mechanical hydraulic system.

Other fuel-saving enhancements include the air conditioning power supply disconnecting from the drivetrain when not in use. When not needed, the pump decouples and uses only 200 watts, or 10%, of the normal power needed to drive a conventional pump. Even flaps behind the kidney grille improve economy, closing for improved aerodynamic efficiency should the engine require less airflow. This feature also improves cold starting times and reduces start-up noise, BMW said.

The automaker has also recently launched a new 420hp, four-litre V8-powered M3 sedan in the UK, supplementing the existing coupe launched late last year and the convertible model due out next month.

“The M3 saloon comes to the UK at a time when customers are increasingly keen to marry high performance with practicality,” the company said, acknowledging that the sedan body style had skipped a generation.

Full-year sales are expected to be around 400 units on top of 1,700 coupes and 900 (folding hardtop) convertibles. Leather upholstery and top-level navigation are standard and a seven-speed twin-clutch automatic gearbox will be optional from July.

Changing gear using either paddles on the steering wheel or the gear selector, the new ‘M DCT’ gearbox uses two wet clutches, one controlling gears 1, 3, 5 and 7 and the other controlling gears 2, 4 and 6. Gear changes are made in only a few milliseconds and the next gear selected in readiness.

BMW says an M DCT-equipped car outperforms a manual gearbox car in outright performance, economy and emissions. An M DCT-equipped M3 saloon is 0.2 seconds quicker from zero to 62mph (100km/h) at 4.7 seconds.

Fuel consumption figures on the ‘official’  EC combined cycle are similarly improved with 23.7mpg recorded compared with 22.8mpg. CO2 emissions are also 10g/km less at 285g/km. The enhancements, both in terms of power, economy and emissions, can be directly linked to the fact a gear is always engaged for the optimum use of energy, the automaker said.

BMW (UK) data show the ‘average’ M3 customer is between 30-50 years old and is either a highly paid professional or the owner/partner of a business.

More than 90 per cent of buyers are male and, while most own another car, the M3 that is the ‘daily driver’.

“The introduction of the M3 Saloon is set to underscore the deserved sobriquet of ‘everyday supercar’,” the company said.

Graeme Roberts