AMG S63 review: the new 5.5-litre twin-turbo V8

AMG S63: a more efficient V8

AMG’s naturally aspirated 6.2-litre V8 sounds like Viking hordes heading for Valhalla. It ranks among the finest engines ever made, so its replacement - a completely new 5.5-litre twin-turbo V8 making its first appearance in the confusingly labelled S63 - was always going to be met with some scepticism.

That is particularly true because AMG is going ‘green’. Really? Its new chief, Ola Källenius, has launched AMG Performance 2015, saying the company’s intention is “to continually reduce the fuel consumption and emissions of new models... while enhancing the core brand value of performance.” Accordingly, the new engine is 25 per cent more economical, returning 10.5 litres/100km, and emits 30 per cent less CO2 - an astonishing 244g/km. Yet it still produces 537bhp, reaches 100km/h in 4.4 seconds and has a top speed of, well, a million kilometres per hour.

The gains come from cutting capacity from 6.208 litres to 5.461 litres, adding two turbochargers, adopting spray-guided combustion and piezo-electric injectors, fitting an aluminium crankcase, and using four-valve technology with variable camshafts and an air-to-water intercooler. AMG’s ‘controlled efficiency’ package also brings intelligent alternator management, which recovers kinetic energy to recharge the battery, along with the dreaded stop/start system.

In this application, the s/s system identifies the resting point of each of the eight pistons, then restarts the engine by injecting fuel into the combustion chamber whose cylinder has the most favourable piston position. It is clever, although I still do not like it. Select ‘S’ (sport) or ‘M’ (manual), and s/s remains switched off. Frankly, that is for the best.

AMG S63 transmission and Performance Pack

For the first time, AMG pairs its seven-speed multi-clutch gearbox with this new engine. A wet clutch cuts friction losses, while selecting ‘C’ mode immediately shifts into seventh for optimum economy. With 800Nm available from 2,000 to 4,500rpm, it will cruise there indefinitely; naturally, though, it is at its finest in ‘M’ mode with a more assertive right foot.

As with the supercharged Jaguar XJ, it is hard to comprehend how quickly and precisely a huge luxury saloon can be driven. It simply does not get better than this.

Unless you choose the S63 Performance Pack, that is. It raises turbo boost pressure to 1.3 bar, lifts output to almost 570bhp and torque to 900Nm, and increases the top speed to 299km/h. At £8,000 extra, it would be foolish to go without at this lofty level.

What is next for AMG? Judging by this, we cannot wait to discover it.