Audi was more than fashionably late to the SUV coupe gathering with its Q8, arriving almost five years after the Mercedes-Benz GLE Coupe and double that since we were first treated to BMW’s X6. No more time is being wasted however, with a high-performance S model introduced less than a year after the standard car.

The SQ8 follows the S-car template to the letter too. It has a substantial and intoxicating boost in performance and an edgier appearance, with an inevitable hike in the price tag to match. As a (current) range-topper it makes a lot of sense in providing an option for buyers who want a little more of everything, although the main issue is whether the marginal benefit in terms of agility is worth the practicality sacrifice over the SQ7. Either way, anyone looking for a usable and comfortable car of this silhouette is unlikely to be disappointed by the SQ8’s breadth of ability.

Engine, transmission and 0-100 time

The SQ8 borrows heavily from the related SQ7 SUV, including the exceptionally-clever 4.0-litre TDI V8 with its twin sequential turbochargers and electric supercharger, powered by the 48V electrical system. Filling in the gap between idle speeds and the smaller turbo’s start point at around 1,400rpm, the powered compressor helps the SQ8 to deliver its maximum torque of 900Nm from 1,250rpm, alongside 319kW at 3,750rpm. In addition, the engine uses its valve lift system to separate the flow of exhaust gases between the two turbochargers.

The upshot is that the SQ8 is comfortably the most accelerative diesel SUV coupe in the class, reaching 0-100kmh in 4.8 seconds, 0.4 seconds ahead of BMW’s X6 M50d, and running on to an electronically-limited 250kmh.

Technical highlights

The SQ8 comes in two trim levels – standard and Vorsprung – with the latter gaining some significant enhancements such as the all-wheel steering, Audi sport differential and active roll stabilisation. The test car also featured carbon ceramic brakes which will not be offered on UK cars in any specification. All models are fitted with 22-inch wheels, eight-speed tiptronic gearbox, air suspension with specific tuning for the S model and quattro four-wheel-drive with a 40:60 torque split under all conditions.

What’s it like to drive?

Fast Audis are no longer the one-dimensional offerings they used to be, but a car of this size is up against the physics right from the start. However, the driving position mixes the viewpoint that SUV buyers love with the lower coupe roof, at least giving the impression that the centre of mass is lower down within the body.

Instantly the even torque spread of the TDI V8 makes an impression, even if the actions of the electric compressor do not guarantee lag-free operation in all circumstances. For the most part however, a few millimetres of throttle travel release instant urge, with a prolonged press dispatching straights with complete ease. Taking manual control of the gearbox yields even more impressive results. Ultimately the sheer refinement and comfort of the cabin removes a little of the sensation of speed, but the manner in which the SQ8 covers ground is remarkable. There is even a pleasant V8 rumble when the 4.0-litre diesel is extended, even if a dropped window confirms a lot of the work is being done by the standard sound actuator.

The carbon ceramic brakes of the test car are the perfect antidote to the pace on offer, although low take up in UK on the SQ7 has prohibited them from being an option. Where you might expect the SQ8 to struggle most is in the corners, but here the active roll stabilisation fitted to Vorsprung versions really shows its brilliance. The SQ8 simply refuses to tip into a bend almost regardless of entry speed; rather than feeling like there are electronics working overtime to fight the mass, it feels natural, composed and remarkably roll-free. Overambition will get you traces of understeer and ESP intervention, but with 285/40R22 tyres front and rear committment is required.

The Audi drive select system adds artificial steering weight in dynamic mode that detracts from the more natural feeling of the standard mode, while the ride is acceptably firm even in the most extreme setting and impressively comfortable elsewhere. There is still a degree of detachment from the action that can be found in other S-badged Audis, but there is still fun to be had without sacrificing the refinement that most buyers will care more about. MATT JOY