X7-based prototype believed to feature beefed-up 335kW quad-turbo diesel.

Photographers have snapped images of what is believed to be the upcoming Alpina XD7 at the Nurburgring in Germany, giving us an early preview of the tuning arm’s take on BMW’s largest SUV model.

While little distinguishes this camouflaged prototype from the recently-revealed BMW X7, trainspotters will notice the (normally fake) intakes on each side of the front bumper are open, feeding air into a pair of intercoolers.

Reports from overseas claim a scan of the registration plate online has also confirmed this vehicle is owned by Alpina, indicating the performance tuning arm is developing its own version of the X7 – likely to be named ‘XD7’, given it generally tunes diesel versions of BMW SUVs.

It’s believed the XD7 will be powered by a modified version of the 3.0-litre quad-turbo inline six diesel seen in the X7 xDrive M50d, which makes 294kW and 760Nm in ‘standard’ form.

With a bit of massaging from Alpina’s engineers, the beefy diesel is projected to make around 450 horsepower, or 335kW. It’s likely we could see a torque bump too, probably around the 800Nm mark.

The X7 M50d currently claims a 0-100 sprint time of 5.4 seconds – not bad for a 2.5-tonne high-riding luxury barge – on its way to a top speed of 250km/h.

An XD7 could see the benchmark sprint time drop below the 5.0-second mark with a power and torque bump, while the top speed will likely be derestricted given Alpina tends to boast about its vehicles’s high-speed Autobahn capabilities.

While the exterior (and likely interior) seen here are largely the same as the X7, the XD7 version should get an array of Alpina design touches and trims inside and out when it’s revealed in production form – so expect a subtle bodykit with similar styling to other models, quad exhaust tips, along with the massive multi-spoke alloys that are a trademark of the brand.

Additionally, the Alpina XD7 should offer a wide range of high-end trim and upholstery for the cabin, and get unique touches like blue digital instruments with red needles, as is the Alpina way.

It’s believed the XD7 could be on track for a production debut sometime next year, potentially at the 2019 Frankfurt motor show in September.