Pairing of superbly responsive engine and characterful chassis gives largely agreeable results
We’ve extensively driven the Mercedes-AMG SL 55 in the UK, and now arriving is the faster Mercedes-AMG SL 63 variant of this new 2+2 roadster.Both use a twin-turbocharged 4.0-litre V8 engine, but whereas the 55’s has 469bhp and 516lb ft, the 63’s has 577bhp and 590lb ft. As well as electronic tuning differences, the 63’s unit gets tweaks to the intake manifold, exhaust and cooling.Both drive through a nine-speed automatic gearbox with a wet clutch (rather than a torque converter), with four-wheel drive and four-wheel steering also standard. Both have coil springs too, but the 63’s chassis gains revised active engine mounts, an electronically controlled limited-slip differential at the rear and hydraulic anti-roll bars, rather than mechanical ones. Those should let the suspension, which on the 55 we’ve found brittle in places, breathe more freely. The 63 is the only SL to get a front-axle lift, too, and beyond that it has minor interior material changes and some bespoke wheel options.Inside it feels as high-tech as the latest S-Class, with infotainment and driving options abounding, partly on steering-wheel clusters, partly on a big central touchscreen. The front seats are huge and widely adjustable. I don’t think you would want to spend too long in the back, but as a way to get home from the pub with a 4.0-litre V8 rather than the thud of my shoes for aural accompaniment, I would take it.This is a lovely engine. I’ve not yet driven the 55, so I can’t tell you how much more responsive it feels, but when it’s sleety, I imagine you would be as quick in one as the other.More interesting is what happens in the various driving modes. I now see what my colleagues mean about the SL trying to do a lot of things at once: be a leggy grand tourer while adding some focused sportiness to the mix, albeit while not treading on the toes of the actual Mercedes-AMG GT (due in Mk2 form soon).Anyway, in Comfort mode and on poorly surfaced roads, there’s still an occasional firmness to the secondary ride, although that’s mixed with a slightly curious slow pitch and float that I think must come from a looseness to the anti-roll bars. This might be great on a smooth, straight, high-speed road, but on the town and country roads that I took, I found it better to dial up Sport, which seemed to tie down those slow movements more keenly without upsetting the overall ride compliance.In this mode, there’s also more keenness to the way the SL drives, yet more predictability about its movements, too. Moving to Sport+ here is a step too far, though, which all but the most committed to body control will wind back from quickly.In the right mode, then, the SL is an enjoyable car. It’s hard not to like that engine, which has all the urge and more that you could want for wintry March; there’s a fine handling balance and great traction; and, given that it has so many driver-assistance systems, there’s a strong natural cohesion and response to the way it drives, even at the 1895kg it weighs now.However, you knew what previous SLs were for, and they were great at what they did. They were confidently affable convertibles that, latterly and with the right engines, would do convincing hot-rod impressions. This time, it seems keener to be felt as a hot rod (it will do 196mph, after all) with occasional GT leanings, for which it’s not quite isolated enough.That’s forgivable, though. As a colleague joked, you would give anything that still has an engine like this five stars. Not quite, but the SL 63 goes a long way.