Review of the new BMW 335i Convertible

Larger convertibles don't always make the most rewarding driver's cars. Things can come over a bit wobbly with the extra bracing of a fixed roof removed, especially when the model wasn't designed from the outset as a convertible. The flipside of this, when we're talking about the BMW 335i Convertible, is that it's hard to imagine any car fitted with BMW's 3.0-litre twin-turbocharged six-cylinder petrol engine lacking the capacity to at least raise a grin. More usually, it's an engine that turns sensible BMWs into certified hooligans, all of which will be music to the ears of those looking for a four-seat drop-top with serious muscle.

Engineering any folding hard top means putting extra metalwork and electric motors in the rear of the car as well as adding bracing underneath to replace the rigidity lost when the roof got the chop. It all means extra weight but BMW did it anyway with its 3 Series. It was impossible to use this kind of roof, yet still achieve the perfect 50:50 weight balance that BMW insists on for other models in its range. But does anyone really care if the 3 Series Convertible has a rearward weight bias? Porsche 911 owners rarely complain and the most powerful 3-Series engine short of the 414bhp V8 in the M3 should be adequate compensation for keen drivers.

Some time ago, the badge on a BMW would give a clear indication as to its engine size. That's no longer the case. Despite the 335i badge, the engine fitted up front in this car is 'only' a 3.0-litre, much akin to that found in the 330i. Whereas that car develops 272bhp, the 'blown' 335i is good for another 34bhp. BMW could have no doubt turned the wick up on the turbochargers to offer way more power but the key to the 335i Convertible is in offering a turbocharged model with none of the drawbacks of turbo cars. These include a soggy throttle pedal, limp off-boost acceleration, unruly road manners when the turbo is fully on-song and fierce fuel consumption. By fitting a pair of very light pressure blowers, the 335i drives like a larger capacity normally aspirated model, hence the logic behind the badge. Honest.

".from behind the wheel, things couldn't be much rosier in the 335i Convertible"

Translated into numbers, this means a sprint to 60mph in 5.8 seconds and a top speed limited to 155mph. Torque is in plentiful supply far lower in the rev-range than you'd get in a normally-aspirated model. There's a maximum of 400Nm on tap at only 1,200rpm and that's plenty to cope with the extra 210kg that the 335i Convertible carries over the equivalent 3-Series Coupe.

The biggest compliment you can pay the 3-Series Convertible is that there's very little difference between the driving experience in this car and the 3 Series Coupe. BMW has achieved this with significant chassis stiffening to compensate for the absence of a fixed roof. The suspension is more compliant that the Coupe's but that just makes the Convertible more pleasant for cruising about in on a summer's day. The engine is remarkably quiet, even with the top down, so you shouldn't attract attention for the wrong reasons but it builds to an intoxicating snarl when you pin the throttle open.

For a car that boasts 306bhp under its bonnet, the 335i Convertible doesn't draw extra attention to itself. That power output is considerably more than the old E36 generation M3 started life with but there's no M badging, no 'look-at-me' spoilers or door mirrors and precious little to differentiate the 335i version from its lesser convertible brethren. If you're after the ultimate subterfuge, badge delete is a no cost option. If you know what you're looking for, the exhausts, the wheel and tyre combination and the slightly hunkered down stance might give a few clues, but nothing that will swivel heads.

This is the facelifted version of the latest 3 Series Coupe, so there are a number of visual differences between this and the original folding hard-top version but nothing too major. The folding metal roof itself remains unchanged. It's a three rather than a two-piece system. The advantage of this is that you don't need a distended rear end on the car to accommodate the larger sections of a two-piece roof. The downside of stacking three pieces atop each other instead of two in the boot is that when they're folded, there's not a great deal of luggage space left. With the roof in place, you'll get 350 litres of load space. Fold it down and 140 litres is instantly pared from that figure.

The operation of the roof takes a so-so 22 seconds but there are some real practicality benefits offered. Because of the larger glass rear screen and side windows, visibility has improved by 38 per cent when compared to this car's soft-top predecessor. Not only does this mean that rear seat occupants will feel less claustrophobic, it's also an important safety feature, with cars and bikes less able to sit in your blind spot on motorways. The rear seat backrests can be folded flat to provide additional luggage space if the boot isn't cutting it but actually sitting in the rear seats will be a challenge for anyone other than children and pets.

Capability like that of the 335i Convertible doesn't tend to be cheap and BMW want well over £40,000 for an SE model. Opt for the M Sport and you'll pay another £2,500 for its ground-hugging looks and sporty add-ons. All models get leather trim, automatic headlights and wipers, air-conditioning, parking sensors and electrically adjustable seats. The standard gearbox is a six-speed manual but a clever seven-speed double clutch transmission is also available which is well suited to this Convertible model's character.

The powerplant in the 335i is highly advanced with high precision direct fuel injection and each bank of three cylinders getting its own small turbine. BMW claims that this engine is around 70 kilos lighter than a similarly powerful V8 model and this weight saving has easily identifiable benefits in terms of fuel economy and emissions which are enhanced further by BMW's latest EfficientDynamics technology. With a combined consumption figure of 32mpg and CO2 emissions of just 205g/km, the 335i Convertible turns in excellent figures for a car with this level of performance.

The challenges faced in creating a four-seat car with a folding hard-top roof are significant and greater still if that model also has some sporting intent. BMW has been pulling engineering rabbits out of hats for years though and if anyone was going to get the balance right it was them. The 335i Convertible benefits from one of the best engines in the world, which is going to be a boon for any car but it also manages to carry its weighty metal canopy with real agility and composure.

You'll only get adults in the rear seats at a push and the boot is negligible with the roof flooded but from behind the wheel, things couldn't be much rosier in the 335i Convertible. The car feels solid and nimble through the bends but rides comfortably with impressive refinement whether the hood is up or down. Hailing from the upper end of the 3-Series range, it isn't cheap but buyers are on the receiving end of an engineering master class from BMW.

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