Mercedes-AMG is preparing to launch a hardcore, 600bhp-plus V8-powered CLE Coupé.

The new high-performance CLE is the second model in AMG’s exclusive Mythos series, following the open-top SL 63-based PureSpeed that was launched in 2024.

It's currently undergoing winter testing in prototype form in Sweden and is planned to go into limited production later this year ahead of a start to sales and customer deliveries in 2027.

Described as “extreme”, the CLE Mythos marks a decisive return to V8 power for AMG's mid-sized coupé and follows the controversial reception of the four-cylinder plug-in hybrid drivetrain in the latest C63.

It will be powered by the a new twin-turbocharged 4.0-litre V8 that features a motorsport-derived flat-plane crank – the same engine that will enter production in the updated S-Class, which is due to be unveiled on 29 January.

In the S-Class, the V8 is claimed to develop more than 530bhp and 550 lb ft of torque. However, in the lighter, more performance-focused CLE Mythos, output is expected to rise substantially, likely surpassing 650bhp, with torque set to exceed 590 lb ft.

This represents a substantial increase over the existing CLE 53, which has a turbocharged 3.0-litre straight six producing 443bhp and 413 lb ft of torque (443 lb ft with overboost).

The new V8's major power uplift hints at a 0-62mph time comfortably under 4.0sec and a top speed approaching 186mph.

The switch to a flat-plane crankshaft – a layout first used by AMG in the GT Black Series of 2020 – reduces rotating mass, allowing for higher revs, sharper throttle response and improved efficiency.

It also enables more compact engine packaging, making it easier to fit into cars like the CLE without major changes to the engine bay architecture.

The CLE’s chassis will most likely be heavily modified to cope with the substantial extra power.

While full information has yet to be confirmed, the prototype confirms that the new model features a widened front track, greater wheel offset and a lower ride height than the current CLE 53. This positions the car on a level similar to the engineering measures previously reserved for AMG’s Black Series models.

Wrapped around those new underpinnings is a dramatic, track-honed exterior. Among the visual changes hinted at by the prototype is a reworked front end featuring a restyled grille and host of brake and engine cooling air ducts and curtains. It also receives widened front and rear wheel arches and a carbonfibre roof.

The prototype also features a prominent rear wing that will be aimed at providing a significant amount of downforce while on track. The area around the rear diffuser has been modified, too, with four trapezoidal-shaped tailpipe tips replacing the round items on the CLE 53.

With a price of £664,000 and just 250 units made, the SL PureSpeed signals what’s in store for the CLE Mythos when it's officially unveiled later this year: a stratospheric price tag and very low production numbers.