Road Test: Porsche Panamera 4.8 V8 Turbo S 4dr PDK

The one thing the Porsche Panamera Turbo did not need was more speed. A bit of a rethink on the design, yes; even a bit of work on the way it drives, but an upgrade from 493bhp? A quicker 0-62mph time than 4.0secs? Unusually, TopGear finds itself thinking that Porsche had more urgent matters to attend to than making the Panamera go faster.

But more power is cheap to come by. You just have a fiddle with that clever bit of electronics that controls the engine and, Günter's your onkel, an extra 50bhp. Only Porsche didn't do it the cheap way.

What it did was fit new turbos. I ought to be more specific, actually, because the outer casings are the same, it's the little spinny things inside (known as impellers) that are new. Now this is very technical, but it's important, so stay with me. The spinny things are now made of an aluminium/titanium blend that means they only weigh half as much as the old ones (50 grammes instead of 100), and this has several advantages - chiefly that they work more efficiently and respond faster. Porsche has actually measured this - they now spin from rest to 170,000rpm in 0.8 of a second instead of 1.2 seconds.

They also help to deliver an extra 49bhp and 22lb ft of torque, which is justification enough for sticking that S badge on the back. So is this - for an extra £20k or thereabouts over a standard Turbo - a fundamentally different, and better, car?

No. It's just about possible to detect some extra urgency as the turbo boost floods in, and the Panamera is capable of remarkable feats of acceleration, either when jetting out of a second gear hairpin, or blasting past slower stuff on the autobahn. The combo of 4wd, PDK gearbox and plentiful acronyms (PDCC, PTV, PTM, PSM and PASM are all standard) make this a tremendously effective car for getting four people somewhere in a great hurry.

That's how the Panamera likes to be driven, too. It likes to go places in a hurry - it's as if it feels important doing that, so takes charge of the situation, relegating the driver to the role of hanger-on. This isn't much fun, especially as the Turbo S, like all Panameras, proves to have a puzzling ride that shimmies across rough roads. It also always feels big and a touch blunt - like trying to steer a particularly energetic basking shark.

Speed. Speed is what the Panamera Turbo S does well. That's its party trick, its whole reason for being. It's just a shame that Porsche didn't turn its attention to the rest of the car at the same time.