Those figures knock the exceptionally powerful 2021 Mercedes-AMG GT Black Series, with 720 hp and 590 lb-ft, off the top of the AMG heap. It's been displaced by a four-door hybrid that, up until now, we'd been thinking would be called the GT73. There is a chance this naming could crop up in the U.S. market, and we've reached out to AMG for clarification.

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The GT73 name would have further separated it from the already serious non-hybrid AMG GT63 S, which had distinguished itself in 2020 Car of the Year testing as a hard-charging super sports car that just happened to have four doors. Instead, the "E Performance" name that AMG had been floating around since it started dropping teasers that it would go hybrid gets tacked on, making for an unwieldy name that requires some context to realize exactly how "extra" this hybrid GT63 S is. Extra, indeed.

Although heavy at 4,600 pounds, the regular GT63 S packs 630 hp and 664 lb-ft—enough juice for us to praise the regular GT63 S as explosive and ferocious. The mind boggles when it considers what an additional 201 hp and 369 lb-ft are going to do for the car's numbers beyond turning its tires into molten liquid. But that's unfair to AMG's dynamics engineers, who are good at figuring out how and when to put the power down. By the way, the V-8's output figures are unchanged from its non-hybrid counterpart, at 630 hp and 664 lb-ft, and it's paired to AMG's Speedshift MCT nine-speed automatic, which features a multiclutch pack instead of a conventional torque converter.

Let's back up and consider the mechanical package because other than some aesthetic differences and a rear-mounted charging port, it's essentially the GT63 S we know and love. At the rear axle, though, significant powertrain differences begin. The E Performance features what AMG calls an Electric Drive Unit (EDU) on the rear axle, which consists of a 201-hp, 236 lb-ft electric motor, electrically actuated two-speed gearbox, and electronically controlled limited-slip differential housed in a single unit. Just above it, there's a 6.1-kWh lithium-ion battery pack.

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On the less exciting end of the spectrum, this EDU allows for a seemingly meager seven miles of EV-only range. AMG admits as much, stating clearly the in-house-built battery pack is built for performance, not range. It employs an interesting direct cooling setup, where the battery's cells are bathed in a non-conductive liquid, which is pumped to a heat exchanger that takes the waste heat to a front-mounted radiator. This cooling system is intended to keep the battery at an optimal temperature for rapid recharging and discharging, as in high-performance driving when the powertrain is dumping large amounts of energy in (regenerative braking) and out (acceleration). That said, it's light and compact, and AMG says it's able to maintain a usable amount of charge on track thanks to its ability to absorb significant regenerative energy.

The EDU can transfer power to the front axle through a prop shaft to the front axle under certain circumstances, and in higher-performance driving modes, it supports the V-8 by feeding power into the powertrain during hard acceleration. The two-speed gearbox is there, in large part, to increase the top speed. At 87 mph, the motor is close to its maximum speed of 13,500 rpm, and second gear is electronically engaged to support the E Performance's 196-mph top speed.

Speaking of numbers, the claimed acceleration is predictably impressive. We tested the non-hybrid GT63 S 4Matic+at60 mph in 3.2 seconds and 11.6 seconds in the quarter mile. Big, impressive numbers for a heavy four-door. AMG says the 63 S E Performance will do 62 mph in 2.9 seconds, and we'll be eager to see if this is a conservative claim or not.