Mercedes-Benz SLK55 AMG review (2012 onwards)

What: Mercedes-Benz SLK55 AMG
Where: San Francisco, California
Price: £57,000 approx. (to be confirmed)
Available: late January, early February 2012
Key rivals:Audi TT RS, BMW Z4 sDrive35iS, Porsche Boxster Spyder

Summary: new Mercedes SLK55 AMG gets a new 5.5-litre 422hp V8 complete with Formula One technology: more power, more efficiency - more fun?

We like: power to spare, good fun, relative comfort, F1 fuel saving tech is very cool
We don't like: not as involving as some rivals (but then, it is a Mercedes), getting the real world economy to measure up, pricey

GALLERY: Mercedes SLK55 AMG
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First Impressions

The brand new Mercedes-Benz SLK55 AMG is coming out fighting. Where previous versions have suffered from what we'll call 'small car, big engine' syndrome, this new third-generation model deploys Formula One-derived technology in an effort to deliver greater driver enjoyment.

Which is not the same as saying it hasn't got a big engine. In fact, the SLK55 debuts a brand new non-turbo development of AMG's latest 5.5-litre V8. With 422hp it has 22hp more than even the previous super hardcore SLK55 Black Series.

But in addition to improving the dynamic characteristics of the chassis to generate bigger grins, AMG has also been working hard to make its cars more environmentally relevant - and the SLK55 becomes the firm's loudest eco standard-bearer.

How so? Well despite that enormous power output, the SLK55 AMG emits just 195g/km CO2 - making it The Most Efficient V8 in the world right now, and clean enough to best every major rival we can think of while packing at least two more cylinders.

Astonishing. Let's get to it.

Performance

The new naturally aspirated 5.5-litre V8 in the SLK55 uses the same basic block design as the 5.5-litre BiTurbo V8 that began replacing the non-turbo 6.2-litre V8 in bigger AMG Mercedes last year.

Differences include a new intake arrangement, modified valve drive, altered oil supply system and an optimised aluminium crankcase. It keeps the BiTurbo's start-stop system, but the key innovation here is "AMG Cylinder Management"

This deactivates four of the cylinders between 800 and 3,600rpm in light throttle load situations. A trick invented in the USA but also employed by Formula One cars - AMG's inspiration - it significantly improves fuel economy and emissions.

The transition between four and eight cylinders is so seamless the dashboard light is the biggest giveaway; there is a very slight difference to the engine note, but thanks to "variably activated" flaps in the exhaust system - another first for an AMG - you have to really listen to tell.

Tickle the accelerator with any kind of conviction at all, however, and the engine wakes up all eight cylinders in just 30 milliseconds; stomp on the pedal, and the SLK55 goes from strong and silent to screaming madman near instantly.

Flaps open, foot down, and 0-62mph disappears in 4.6 seconds with a wicked, swelling, bassy growl. The AMG Speedshift Plus 7G-Tronic gearbox swaps cogs with conviction, and car sounds positively nasty on the overrun - popping and crackling like the breakfast cereal of the damned.

Sadly, the sense that this aural drama is a bit artificial only gets greater the further you drive, as the 'emotional sound design' built into the exhaust is just so consistent it begins to get a touch annoying after a while.

There's no disputing this is a very fast car - top speed is the usual electronically limited 155mph - but even with all that V8 capacity in full affect it isn't a lazy bruiser. You need to work it hard to properly feel like you're flying.

Ride and Handling

Helping you out on this front is an impressively well-rounded chassis. AMG's recent - and refreshing - appreciation of compliance delivers a car that is largely comfortable yet capable of carrying huge speed through the corners.

Beyond thoroughly overhauling the SLK's suspension, AMG has also increased the steering response by adding its own "Direct Steer" system and something new called "Torque Vectoring Brake".

This subtly brakes the inside rear wheel to help direct the SLK55 into turns with more alacrity - handy when there's all that engine up front. The McLaren MP4-12C supercar does the same thing, incidentally, McLaren having previously been banned from using the tech in F1.

Driven smoothly, the SLK55 is fast, nimble and has masses of grip - though this is quite easily overwhelmed, even in the dry (be warned if you have the stability control set to Sport...).

It's playful, willing, and does a good job of making you feel involved without troubling you with every single detail. It hasn't the intimacy of something like the Boxster Spider, but does high speed finesse with aplomb.

Those looking for a little more can always specify the optional AMG Handling Package, which adds stiffer springs, a limited slip differential, composite front brakes and an Alcantara steering wheel.

Interior

The AMG isn't massively different on the inside to any other SLK; flattened steering wheel, aluminium paddleshifters, AMG sports seats and an optional dashtop IWC clock being the highlights.

The instrument cluster has some additional AMG badging and functions, while a switch on the transmission tunnel swaps the gearbox between Controlled Efficiency, Sport and Manual modes - C, S and M.

As with all third-generation SLK model, you can also have Magic Sky Control. This is a panoramic centre roof panel with a difference for the folding hardtop, allowing you to change the level of tint at a whim.

Genuine wow factor the first time you see it, and great for keeping the car cool in summer while offering an open air feeling with the roof up over winter. That said, the standard 'air scarf' system means there are few excuses for not dropping the top at every possible opportunity - especially given the noise the engine makes.

Economy and Safety

The start-stop system and AMG Cylinder Management only work in the Controlled Efficiency transmission mode - so if you think it might be annoying and/or unnerving don't worry, you can just disable it altogether by switching to Sport.

We recommend you give it a go, though, as both devices worked flawlessly in our experience with the car, and are the major reason the economy is 30 per cent better in this SLK55 compared to the one it replaces.

Alongside that amazing 195g/km CO2 figure, this translates into an official combined fuel economy figure of 33.6mpg. Clearly, you aren't often going to achieve this in real life, but AMG says the fuel saving tech is actually more beneficial in real world driving than in the lab.

As for safety, the SLK55 is available with almost every Mercedes gizmo going. This means it can check you're not falling asleep, read road signs, optimise lighting patterns, activate the brakes - plus it includes the latest rollover protection from the regular SLK.

Verdict

The new Mercedes SLK55 is a very, very good all-round high-performance sports car, which outmatches its obvious rivals in many major areas. It has more power with greater efficiency, offers a folding hardtop roof, and is now much closer when it comes to the drive.

All this comes at a price, of course. Mercedes UK doesn't anticipate a major rise over the existing version when the new car arrives here at the beginning of next year - but at around £57,000 that's a cool £10,000 above the most expensive opposition.

In the end it comes down to not only your budget, but the way you like to drive. If you're after something raw and intimate then the SLK55 isn't it; those searching for a more complete ownership experience, however, should absolutely take a gander.

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