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New Mercedes-AMG C63 swaps V8 for 670bhp PHEV system

The new Mercedes-AMG C63 S, due later this year, trades its iconic V8 engine for a 670bhp plug-in hybrid powertrain that combines a 469bhp 2.0-litre four-cylinder and a 201bhp electric motor on the rear axle in a sophisticated four-wheel drive system.

As before, the C63 will be available as a saloon or an estate, but the role of the two-door coupé and convertible will be picked up by a hot version of the incoming Mercedes CLE, which replaces two-door versions of the Mercedes C-Class and Mercedes E-Class. For this new generation, the non-S C63 base model is dropped, leaving only the Mercedes-AMG C63 S E Performance, to use its full name. 

Visually, the C63 is obviously differentiated from the regular C-Class by 76mm-wider front wheel arches hiding 19in or optional 20in wheels. There’s a more aggressive front valance with the typical AMG grille and active shutters that open or close depending on the engine’s cooling demands. The additional cooling hardware actually means the bumper juts out more than on a standard C-Class, making the whole car 50mm longer. The bonnet, with its air outlet on top, is unique to the AMG too. 

Engine

The 2.0-litre four-cylinder engine is a development of the unit found in the C43 and SL43. However, in this application, it has a lower compression ratio (from 10:1 to 9:1) in order to accept more boost from the larger turbocharger. To minimise lag, the turbocharger incorporates an electric motor that runs off the 400V electrical system and helps the turbine spool up faster – technology derived from AMG’s Formula 1 racer.

With 469bhp and 335lb ft of torque, the engine on its own is the most powerful four-cylinder currently in series production.

It’s supported by an electric drive unit (EDU) on the rear axle, which combines a 201bhp, 236lb ft electric motor, a 6.1kWh lithium ion battery, a two-speed gearbox and an electronically controlled limited-slip differential in one unit. This EDU is similar to the one on the new GT 63 S E Performance, although in that application it is paired with a 4.0-litre V8.

Like other AMGs, the engine still drives through a nine-speed automatic gearbox with a wet multi-plate clutch.

At 6.1kWh, the high-voltage drive battery is relatively small for a plug-in hybrid. As a result, the C63 can travel on electric power for only eight miles, compared with the C300e’s segment-leading 68 miles of EV range. AMG product manager Arne Wiebking said: “This car is not made to drive fully electric for long distances. This car is made for performance.”

The purpose of the electric drive mode is more for social acceptability and leaving quietly early in the morning. The real value of the electrified drivetrain lies in providing the instant power that the petrol engine can’t.

According to Wiebking, it’s not even essential that owners plug the car in. With many plug-in hybrids, once the battery is empty, they reduce the amount of electric power available and since it’s not efficient to recharge the battery using the engine, they usually don’t. The new C63 manages its energy differently.

Combining the strong electric motor, high-performance battery and direct cooling for the battery cells, the C63’s hybrid system can regenerate over 100kW of electric power under braking to feed back into the battery and give it the best chance of staying topped up. For extended hard driving, a ‘boost mode’ can also use the engine to ensure that the battery capacity never drops below 30%. 

Four-wheel drive

The C63 beats its rivals to adopting plug-in hybrid power, something that the Audi RS4 and BMW M3 aren’t expected to do for a few years. However, it is the last to offer four-wheel drive.

“The all-wheel drive system is one big plus for this car, because that was a pain point for our customers with the outgoing car”, said Wiebking, adding that a lot of owners felt the old rear-drive car was sometimes too much to handle. 

Unlike the C43, which has a fixed 31:69 torque split, the C63’s 4Matic+ is fully variable and can adjust the torque distribution depending on the drive mode and the circumstances. Like its big brother, the E63, it also has the ability to decouple the front axle in a dedicated drift mode.

Although the electric motor is mounted on the rear axle, it can also send power to the front when required. This means that even in EV mode, the C63 drives all four wheels.

The new C63 PHEV tips the scales at 2111kg. For comparison, the BMW M3 xDrive weighs 1780kg.

To keep that mass in check, AMG is throwing its entire arsenal of technology at the C63. At the front, the steering knuckles and supporting joints for the spring link are bespoke and lengthen the wheelbase by 10mm compared with the regular C-Class.

It still sits on steel coil springs, but uses a set of remote-reservoir dampers with a solid piston and external valves for bump and rebound. This improves damping performance under extreme conditions and results in both better control and more comfort. Unlike the racing dampers on which such a system is more commonly seen, the C63’s are electronically adjustable via the drive modes in three stages.

The C63 also gets four-wheel steering, allowing the rear wheels to turn up to 2.5deg in the opposite direction to the fronts (up to 62mph) or up to 0.7deg in the same direction at higher speed.

The C63 also gets upgraded brakes with six-piston calipers at the front (optionally gripping composite discs) and single-piston items at the rear. The friction brakes are supplemented by strong regenerative braking, adjustable through four stages.

Q&A: Jochen Hermann, chief technical officer, AMG

What was your aim with the new, hybrid C63?

“The way you drive this car, for us, is changing the game. The difference between the C63 V8 versus the new C63 S E-Performance is all about electrification. We are increasing performance while increasing the efficiency of our powertrain. I think that’s very unique. This is what happened in Formula 1 and this is what we bring to the C-Class.

“And in order to do that, we took on board a lot of the software learnings that we got from the Formula 1 team, and especially from our Mercedes-AMG One project. And you know, since it took us a while to develop the AMG One, you can imagine there was quite a lot of learning. It’s all about energy management. If you’re not able to manage the energy in a P3 hybrid, then you might do one lap on the track and your battery would be empty. And that is why we put many more driving modes into the car. You have to make decisions, like Lewis Hamilton or George Russell would do.”

The V8 is a defining feature of many AMGs. How do you sell customers on this new, very different car?

In these times, it’s essential that we convince our customers and future customers of this new kind of technology, this new kind of game. I think an AMG always works best when you drive the car. The likelihood that you buy the car is always higher when you drive it than if you just look at it and read some specifications. We try to make it clear that we didn’t just get rid of four cylinders. No, we added a lot more things. For example, the electric drive mode. Early in the morning, late at night, leaving your house fully electric – that’s also something that people these days like. We have some very easy ones that can bring people to this car. For example, people said they missed all-wheel drive in their C63. Now they can have it.”

Is there an expiry date for the V8 in other AMGs?

“First of all, the V8 remains very important for us. We are facing new challenges with EU7 [emission regulations] and this kind of legislation, but the V8 continues to be an important part of AMG. But because of the size of the engine and the weight balance, there is quite a natural limitation to which models it’s still suitable for, considering the additional weight, but also the performance of these E-Performance models. From the GT 63 upwards, I think a V8 makes sense, and in a C-Class, a four-cylinder makes sense.”

Will this be the last C63 with petrol engine?

I wouldn’t want to guess whether it is the last, but there is one thing that we have said: AMG will also introduce a full-electric architecture, AMG.ea, within the next couple of years, with several models based on this architecture. So our future is based on three pillars. One is powerful combustion engines – the V8, for example. The second is electrification of powertrains going into the E Performance direction. And then the third pillar will be that in the future, we will have high-performance, fully battery-electric driver’s cars.”

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