The future of Mercedes-AMG’s downsized four-cylinder plug-in hybrid (PHEV) powertrain is looking murkier than ever, and ironically it’s emissions regulations that could see it dropped in favour of a six or V8.
“Technically, the four-cylinder is one of the most advanced drivetrains available in a production car. It’s also right up there on performance. But despite this, it failed to resonate with our traditional customers. We’ve recognised that,” a senior insider told Autocar.
The C63 S E Performance and GLC63 S E Performance – which entered production in 2022 and 2023, respectively – are the only Mercedes-AMG models that use the turbocharged 2.0-litre PHEV powertrain, and it’s reportedly now set to be phased out.
Instead, Autocar says future Mercedes-AMG models using a petrol engine will be powered by either an updated version of the performance brand’s inline six, or an all-new flat-plane crank V8.
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“There’s no doubt about its potential – this is one of the most sophisticated engines we’ve ever built – but the investment to make it EU7-compliant is very high,” the source said of the M139 turbo four at the heart of the C63 and GLC63’s PHEV powertrain.
The German automaker will reportedly therefore axe the M139 engine, which is also used in models like the A45 hot hatch and CLA45 sports sedan, and that could also see the SL43 roadster – the first four-cylinder SL in more than 60 years – move to a six-cylinder engine.
That would see Mercedes-AMG vehicles feature either a six- or eight-cylinder engine, or an electric powertrain.
“AMG will continue with a dual strategy – two pillars. The electric pillar will grow significantly. But the second pillar – hybridised internal-combustion engines – will also remain,” Mercedes-Benz chief technology officer Markus Schäfer told journalists recently.
“AMG and Mercedes are working together on a brand-new V8 engine. That engine will support upcoming emissions regulations. There will still be six- and eight-cylinder units, all electrified with either 48V systems or full hybrid set-ups.”
Autocar previously reported the C63 could adopt a 3.0-litre inline-six plug-in hybrid powertrain – like that in the E53 – as soon as 2026, potentially with outputs exceeding those of the current four-cylinder C63 (500kW of power and 1020Nm of torque).
In the E53, the inline six produces 330kW and 560Nm, and is mated with a 120kW/480Nm electric motor integrated into the nine-speed automatic transmission, for total system outputs of up to 450kW/750Nm.
However, the current C63 apparently won’t support the new V8, even though the related CLE63 is said to be in line for it.
“It requires more space, not just in terms of physical dimensions but also for associated cooling systems and crash protection measures,” Autocar was reportedly told.
Mercedes-AMG has previously acknowledged it has lost customers in the switch from a twin-turbo V8 to a plug-in hybrid turbo four in its BMW M3-rivalling C63.
“We see that some of our very loyal customers struggle a bit with the concept. Of course, no doubt we have also lost some customers who are just into V8s,” Mercedes-AMG boss Michael Schiebe told Car earlier this year.
“The C63 is a very important car in our portfolio. It used to be, it is and it will be. We decided with the current version to really go for the latest technology. We wanted something new and that’s why we put the F1 powertrain into a street-legal car.
“We jumped far ahead with this technology, but we should have explained the technology more to our salespeople and customers. We will continue to do that and further improve.”