The 53 donkey is a 3.0-litre, and of extraordinary complexity. Deep breath. It’s an in-line six-cylinder petrol, mounted longitudinally, all of whose exhaust outlets pass through a single, large, twin-scroll turbocharger, mounted high and near as damnit next to the exhaust ports. To cover the inevitable turbo lag from this, though, there is also an electrically powered compressor, located on the other side of the block, just before an intercooler right next to the inlet ports, which can help suck air through the induction tract before the big turbocharger is boosting properly. Following? Good.
The inlet for that compressor comes after the big turbo, where a variable stopper in the main inlet tract, which runs around behind the engine, can divert a little, or all, or any combination – in reality, it’ll be varying the proportion constantly – of air through a smaller tube to the electric compressor, after which, suitably pressurised, it flows back to the main inlet tract just before a throttle butterfly. Still following? Sigh, me neither. Anyway, it makes 429bhp and 389lb ft, which is quite a lot in itself.
But in addition to both of these forced inductors, mounted between the engine and the nine-speed automatic gearbox sits an integrated starter/generator (ISG), an alternator/starter motor and flywheel combo, which can contribute 21bhp and no less than 184lb ft to the engine’s already imposing output. But rather than it just spinning up to reduce turbo lag, which doesn’t necessarily help increase pressure into the intake system, it’s apparently just as useful for it to drag slightly at low revs, developing electricity as it does, which it passes on to the electric compressor, and it’s that which spools the inlet pressure by dragging air through the turbo, helping that to spin up as it goes, too, thus reducing overall lag instead. Right? Look, I don’t know, my head hurts. I suppose the short of it is that getting air through the engine is key, so inlet pressure rather than engine speed itself is king.
Ultimately, though, all of this power goes to the CLS’s rear wheels most of the time, with a standard all-wheel drive system on all models diverting it to four wheels when the rears threaten to slip. Unlike, say, the E63 AMG, you can’t lock the 53 into rear-drive mode for adolescent slides.
Which is perhaps just as well. Our drive takes place in Spain during the first time for about a decade that it has experienced snowfall. So our CLS53 is wearing winter rubber, which, AMG engineers tell me, will reasonably well soften the way it grips and steers.
One of the challenges of the 53 was, by all accounts, to make it feel sufficiently different from a regular CLS to satisfy AMG boss Tobias Moers, who’s quite particular. Full-fat AMGs do have quite a distinct character: they’re loud, brash and way more capable these days than the hot rods they were a decade or so ago but still dominated by their V8 engines.
That’s a harder character to inject with a straight six, obviously, especially one whose exhaust is so muted by turbo and which, by definition, is a bit semi-skimmed next to a 63. But the engine is sparky. It’s by no means loud, but throttle response and linearity really are exceptional, with a rev limit at nearly 7000rpm and a character and note that has shades of BMW M car. It’s a belting engine, in fact. I wonder if Aston Martin, part owned by Daimler as it is, has thought about one day dropping one into a Vantage.