The Bovensiepen Spider is Old Alpina’s 430bhp modified BMW Z4

Remember Alpina? Not the new BMW iteration, but the old one that did stuff like this. Old Alpina is now called Bovensiepen – after the man who started the original company – and continues to knock out modified BMWs.

Like this one. It’s called the Bovensiepen Spider, and as thine eyes will attest, it is a modified BMW Z4. Straight-six up front, two seats in the middle, much power exiting the rear.

Indeed, Bovensiepen’s upped the power from BMW’s long-serving 3.0-litre inline turbo, here delivering a very healthy 430bhp and just under 430lb ft – more than the standard car’s 355bhp and 369lb ft, you’ll note – via an eight-speed auto to the rear wheels.

Only a few tenths quicker to 62mph, mind, that time now 4.2s instead of 4.5s, but the top speed with the Performance Pack fitted rises to 183mph. And it’s one of Old Alpina’s strengths: engine mods.

That ‘B58’ sixer gets an “unrestricted” air intake duct featuring an additional ram air channel, a larger intake silencer, and a new exhaust system that reduces back pressure (age comes for us all, Z4) and gives it a “sporty” and “bass heavy” sound. There’s better cooling, too.

And tuned dampers (more compression at “low damper speeds”), longer aux springs at the back, and the option of bigger, more powerful brakes with four-pot calipers.

Oh right, the Performance Pack. That adds a rear aluminium diff cover with larger cooling fins, that top speed increase, and an underbody V-brace to better stiffen up the Z4’s chassis.

McLaren P1 designer Frank Stephenson – who tells Top Gear which cars he thinks are hot or not – has tweaked the Z4’s exterior, just as he did with the Bovensiepen 05 GT. Here he’s added a new front splitter, side skirts, rear diffuser, a rear spoiler and 20in lightweight forged alloys. Ever so subtly different, just like you’d expect from Old Alpina.

Inside there’s lots of leather, Alcantara, and the option to customise the life out of it. Not least because Bovensiepen is building just 99 of these Spiders, with prices starting from €115,500. Customers will get their cars from 2027 onwards.