Mercedes-Benz SL63

When it's time to reheat an existing model it's odd for a car company not to bump power up even a few token kilowatts, but the new Mercedes-AMG SL63 is probably the one car that could get away with it.

It more or less carries over its 5.5-litre twin-turbo V8 with the same outputs as before, few customers apparently complaining that 430kW and 900Nm weren't enough.

Instead the changes to Merc's timeless SL are mostly cosmetic, the front end completely restyled, grafting on a version of the new corporate face.

A new rear bar with diffuser is about the extent of rear styling changes, the interior also copping more software than hardware tweaks.

And with the 463kW/1000Nm V12 SL65 sadly axed from Australia as of this facelift, it now means the 63 is the fastest SL you can get.

The SL63 misses out on the new 9-speed gearbox adopted by SL400 and 500, it not being able to take the torque. But instead AMG insists the 7-speed wet clutch automatic now shifts noticeably faster than the previous model.

Active suspension is the big news in the chassis department, the SL getting something called Active Body Control, effectively replacing conventional sway-bars with computer-controlled dampers working against dive, squat and roll.

The plushly-sprung SL63 probably needs it, particularly given it'll do 0-100km/h in 4.1 seconds with launch control. With an engine very much about torque than revs, the SL63 slams you back from even low in the rpm band with enormous levels of turbocharged shove. And charges past 100km/h like it's in a hurry to hit its 300km/h limiter.

To the uninitiated the SL63's acceleration will feel like a top fuel dragster. And even for someone who's owned a fast car or two before, its relentless urge will take a long time to wear off.

Behind the wheel you sit fairly rearward in the SL and peer over a long, wide bonnet. It feels like two thirds of the car is in front of you rather than behind - partly confirmed by 51.2/48.8 front-rear weight distribution - a sensation of forward mass that can make setting the SL's trajectory difficult to judge for the first two dozen corners at least.

There are more intuitive front-ends around but with time you and the SL start to gel and it becomes less of an issue. And the 63 in particular is only too eager to cast aside its luxury cruiser personality with the press of a few buttons.

In A45, C63 and GT S the Sport Plus setting is much too stiff for the road but in the SL63 it's pretty much perfect for a mountain blast, the big Merc sitting impressively flat, keeping its cool over bumps with no scuttle shake as it leans into sticky Michelin Pilot Super Sport tyres.

Luxury-tuned steering (now with a "constant and more direct ratio") isolates against vibration around town but the trade-off is very little steering feel, understeer felt more through the seat of the pants than the hands if you push too hard.

Out back, two rear 285/30ZR20 tyres transmit the teutonic 900Nm to tarmac with notable effectiveness. But on corner exits, thanks to a mechanical limited slip diff the rear is only too willing to wag and lay big black lines with a provocatively-applied throttle, even in the satisfyingly lenient Sport ESP setting.

The SL63 has tonnes of lateral grip and conceals its 1770kg well, probably no small thanks to the imperceptible workings of the Active Body Control.

Reconsider optioning the carbon ceramic brakes - on our test the pedal started to soften and lengthen towards the end of a punishing downhill run.

Switch the settings back to Comfort, though, and the SL63's personality turns instantly to lazy cruiser with incredible ride for 30-profile tyres and a serene, breezy interior even with the roof down at highway speeds.

For all AMG's tweaks, the SL63 is plainly one of its more sensible models, deliberately avoiding most of the attention-seeking ostentatiousness of its stablemates and shunning even an active exhaust button.

That said the engine is still loud enough with a lower-frequency V8 burble and the occasional crackle with downchanges.

But the SL63 impresses most in the way it strikes a balance between lazy top-down boulevard cruiser and tear-your-face-off performance weapon. In this AMG has done an excellent job.

While there are convertible sports cars more intuitive and precise than the SL63 they won't "cruise" anywhere near as sublimely and AMG is the first to admit the SL63 is not made for the track. They know most SL63 customers will have another car for that.

Mercedes-Benz Australia says the facelifted SL63 will come in under the current car's $399K when it goes on sale in Australia in July.

4 out of 5 stars

Specifications

Engine: 5461cc V8, DOHC, 32v, twin-turbo
Power: 430kW @ 5500rpm
Torque: 900Nm @ 2250-3750rpm
Weight: 1770kg
0-100km/h: 4.1sec (claimed)
Price: $385,000 (estimate)