Alpina, which makes this Alpina B4 Biturbo Convertible, is one of those companies you’re simply glad still exists. It’s considered to be a car maker in its own right rather than just a tuner, yet although it’s independent of BMW, the two companies get on so well that Alpina has access to BMW prototypes and advance information so it can release its cars before BMW’s own performance arm, M division, delivers its M cars.
This B4 Biturbo, then – tested here in open-top form – is the equivalent of BMW’s M4 coupé and M4 Convertible, only with Alpina’s usual twist: whereas a BMW M car is usually quite hardcore, an Alpina is designed to deliver a more relaxed performance car experience. It prides itself that its cars ride better than BMW’s equivalents, and if they’re slightly less focused drivers cars, then that’s fine.
The B4 Biturbo, then, takes the 435i Convertible (or coupe) as its base and Alpina fits its own suspension tuning, wheels and (non run-flat) tyres, amends the interior and, most notably, fits twin-turbochargers in place of a single turbo to the 3.0-litre engine, and in doing so creating a 404bhp open-top that it prices at more than £60,000.
What’s the 2016 Alpina B4 Biturbo Convertible like to drive?
When Alpina says it fits tyres it has developed with Michelin and that they’re not run-flats (which have very stiff sidewalls so you can drive on them for a while following a puncture), it says so for a reason: it wants you to know that the B4 Biturbo is more comfortable than its BMW equivalent.
And sure enough, there is an underlying suppleness to the B4 Biturbo Convertible’s ride, but you should be aware it’s neither as smooth nor as isolated as that of the coupé variant. The opening roof occupies a big area, which means there’s a lot of bodywork missing that would otherwise increase the body stiffness. In turn, that means the B4 feels a little less precise than the coupé. It still handles well, though, with weighty steering and high levels of grip.
It’s fast, too, but with 404bhp it was never going to be anything else. The changes wrought to the engine, plus a sports exhaust, give it a hollow, rasping sound at low speeds, but it retains its smoothness as revs build, while the eight-speed automatic gearbox – there’s no manual option – shifts with impeccable smoothness.
There aren’t many direct rivals to the B4 Biturbo. There’s the BMW M4, obviously, but apart from that the Audi S5 is probably the next closest (now that the RS5 is discontinued), and for our money the B4 gives the more satisfying driving experience.
What’s the 2016 Alpina B4 Biturbo Convertible like inside?
Inside, Alpina has tweaked the B4 in the way it knows best. It leaves all of the BMW fittings in place, and just adds to them with high-grade-feeling materials to improve the fit and finish.
There’s leather, then. Lots of leather, adorning the seats in fine fashion. It’s pleasingly stitched, but the seats themselves are BMW’s own design, and absolutely fine for being that. They sit behind (or in front, depending on how you think about these things) a dashboard that’s sensibly laid out and – small Alpina plaque and trademark blue dials aside – standard BMW fare. That is no bad thing, either. BMW’s iDrive infotainment system is these days one of the best on the market, the sound system is excellent and the ergonomics are top notch.
Alpina does fit its own steering wheel, and that’s also a good thing. With a thinner rim than the BMW one it seems to make the steering feel more accurate; although in place of large paddles to shift gears there is instead a pair of small buttons.
The Alpina is a four-seater – that’s one of the benefits of having such a large open area, of course. Knee room is fine for kids, and although there’s a bit of wind buffeting in the back with the roof down, it’s perfectly acceptable. And behind all that there’s a reasonably sized 370 litre boot.
Should I buy one?
The B4 Biturbo sits in a pretty small niche, even as a coupé; as a convertible it’s in a smaller one still. You’ve got to want good performance and traditional sports car handling, yet ask for both of those to be combined with four-seat, open-topped motoring – which inevitably brings compromises in all kinds of places.
It’s not an easy set of objectives for any car to fulfil, but the B4 Biturbo does it better than most cars manage – not that many try.
As a result, then, if you’re thinking about choosing something with such rare groove characteristics, the Alpina would be our favourite choice. That it’s a bit more relaxed than a BMW M car really suits a convertible, while the rarity of the brand means that residual values should stay strong and there are always a few enthusiasts who’ll like the cut of the Alpina’s jib. Just be prepared for a car that, inevitably, ends up with a few compromises along the way.
What Car? says…
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Alpina B4 Biturbo Convertible
Engine size: 3.0-litre 6cyl twin-turbo petrol
Price from: £62,950
Torque: 443lb ft
Top speed: 187mph
Fuel economy: 35.3mpg
CO2 emissions: 186g/km / 34%