Mercedes-Benz engineers at AMG, keen to regain market share from cars such as Aston Martin's Rapide and Porsche's Panamera Turbo, have been working overtime to ensure the second-generation CLS63 AMG is (very) dynamically able.The driving force behind this new CLS is a smaller engine than the outgoing 63 AMG that manages to be both more powerful and efficient. SMALLER IS BETTERMerc’s new M157 engine displaces 5.5 litres and has two turbos so, in terms of configuration, it’s very similar to the 65 Series AMGs, just lacking the additional quartet of cylinders and a half-litre of swept capacity. Instead of employing variable-compression turbochargers, the M157 engine’s boost regime is fed by a simple Garrett-Honeywell turbo per cylinder bank. These turbines provide two ranges of boost; 1 bar for series production CLS63 AMGs and 1.3 bar for cars running the optional performance pack. The compression ratio, for a large-capacity turbocharged engine, seems a little on the high side (10:1) yet an AMG engineered air-to-liquid intercooler chills inlet temperatures down to around 90 degrees. Despite being smaller (and controversially featuring forced induction), the new engine is statistically superior to the M156 6.2 V8 it replaces.Output figures for the new (smaller) engine are 400 or 420kW, the latter benefiting from an optional performance pack. Peak rotational force runs to 700 and 800Nm respectively. All round, the improvements over Merc’s outgoing 386kW/630Nm 6.2 V8 are plain to see.A new seven-speed MCT transmission drives the rear wheels and AMG’s engineers have increased efficiency (by reducing drag, binning the torque converter) and performance. The CLS63 AMG storms to 100km/h in 4.4sec; performance pack models trim off another tenth. Top speed is limited to 250km/h though the performance pack allows 300km/h. AMAZING EFFICIENCYBeyond the increase in pace, the new CLS63 uses 34% less fuel than its naturally aspirated predecessor, averaging (according to AMG) 9.9 litres/100km in the combined consumption cycle.To ensure harmonised performance, AMG engineers have ensured the CLS steering and suspension components are suitably improved to cope with the 5.5 turbocharged V8’s performance. Adaptive shock-absorbers, a 24mm wider front track and (most importantly) a new electro-hydraulic sports steering system should ensure delicate control when gathering up power slides – which have always been a fait accompli with any CLS63.Distinguishing the 63 AMG from its lesser CLS siblings are wider wheel arches, a larger contoured bonnet, rear diffuser and composite boot-lid spoiler.The CLS63 AMG should go on sale locally by April next year.