Road trip: Porsche Cayman GT4 from Germany to the TG track

Twelve hours. Brief enough that you could waste it and not feel too regretful. Long enough that you could spend it well and bank memories to last a lifetime. Which I intend to do now.

Video: watch the Cayman GT4 in action on the TG test track

The grey Porsche factory in Stuttgart glows shades of peach under the sun's evening rays as the security guard hands me the key to a Cayman GT4. My 12-hour clock starts ticking. An all-nighter will see us across to England via autobahns, back roads, forested hills and open plains. Tomorrow morning, the gates to the TopGear track will unlock, and with them, this car's Porsche Motorsport soul will open wide.

Pictures: Rowan Horncastle

This feature was originally published in the May 2015 issue of Top Gear magazine

It lurks with intent by the gatehouse, its stance squatter and wider than the regular Cayman's to a drastic extent. Its body is emphatically reshaped and augmented and pierced, for cajoling the air into holding it to the road and cooling its workings.

Indoors are seatbelts in Racing Yellow (a colour that's worth a second a lap, obvs) which hold you in a pair of featherweight carbon-fibre-shelled seats from the 918. Also for lightness' sake, the radio-nav-phone unit has been replaced by a Porsche Motorsport-approved blend of nitrogen and oxygen.

A Cayman S is a wonderful sports car, a Cayman GTS a tautened version of same. But in the first few hundred yards, out the gate and round by the Porsche Museum, it's abundantly clear a Cayman GT4 really is something else entirely. The reduced essence of a track-focused supercar: smaller, less powerful, but exhibiting all the same behaviours and sensations.

Start it and the engine shimmies with a hollow metallic bellow. The pedals act without an atom of slack or indecision. The steering, too, brooks no nonsense. Drive off and the transmission's teeth mesh with a whine; drive off with some lock on and the diff judders. The ceramic brakes grind slightly, the tyres slap, the suspension conveys every nuance of what's passing beneath.

You accept these small privations as the prerequisites of a transcendentally engaging fast car, a car that will talk to you as clearly as glass and react to you as sharply as a shard. And they're making my whole nervous system tingle in anticipation as I nudge it gently out through the Stuttgart suburbs.

Reaching the autobahn, I go for it. The evening traffic is thinning, but not yet thinned. A gap opens and the flat-six simply fills its boots, gorging its way through the mid-revs the instant my foot moves, climbing on the cam between 3,500 and 4,500 and then howling into sixes and sevens, its red line at 7,800. Change up and it drops things right onto the peak of the wave.

And again, until the 100mph I was sharing with other outside-lane traffic has swiftly morphed into 130, 140, 150, the chassis confidently tucked down by its aerodynamics and iron-willed damping. Suddenly, the yellow streak has hoovered the next knot of traffic back towards itself, and the carbon-ceramic brakes must do their thing. Which they do with ridiculous ease.

Peeling off south of Pforzheim, we're in the Black Forest as the light in the sky sighs its last. These are superb roads, carving their path through the dense trees in busy combinations of sweepers and hairpins. No car is faster than its headlights, and the GT4's adaptive pair swing their blaze of xenon with your eyes as you turn the wheel. There follows a whole lot of that as we climb out of successive valleys, across the ridges and plunge down again, building and releasing forces in every direction.

The GT4's front suspension and brakes come almost unadulterated from the 911 GT3. At the back, it keeps the usual Cayman design, but solid ball joints replace certain rubberised bushes. Here in the Forest it comes out to play. All my actions bring a high-precision zero-delay response, the car instinctively alive to my intentions.

It feeds back to me, too - the steering full of feel in a way none of the Caymans and Boxsters have managed since the hydraulic-assist days, but with much more sharpness. My hands are kept busy, too, by another throwback I'm cherishing: a manual gearbox.

Now, in the matter of powertrain, it's true the Porsche Motorsport engineers were forced to bend to the mundane forces of commerce. A special engine or gearbox were ruled out by their expense. Instead it's the 3.8-litre flat-six out of a Carrera S, good for 380bhp. So it doesn't take you to the stratospheric revs of the true motorsport engines.

But its instant reactions, strong torque and charismatic noise - gingered up by the special exhaust and the fact the whole lot sits your side of the rear windscreen - mean it could hardly be any less of a letdown.

A slightly bigger irritant is the fact that the GT4 keeps the standard Cayman gear ratios. Second and third are too high for these tighter sections of forest. But, again, there's a compensation. The shift travel is shortened and the lever finds its slots with strongly detented, steely certainty. Like a Porsche shift, only Porschier.

And, heck, the actual performance nonchalantly bats away any cavils: it's up for 62mph in 4.4 seconds (60 in 4.2), and will travel onward to 183mph. Porsche doesn't make a big deal of weight saving versus the standard Cayman, but 1,340kg with fluids is hardly flabby.

So, here in the woods and hills, I'm deep into a world of my own, submerged in the inky texture of trees whizzing by, chasing the narrow pool of light and tarmac, ears full of the flat-six concert, feet and hands and head utterly absorbed in this three-way dance between them and the car's mechanisms and the road itself.

This carries us much of the way to the Rhine. Picking a bridge to France, we're connected to the autoroutes. If we're to make the TopGear track slot, it's time to put on some steady, brisk miles. No one goes fast on French motorways these days; 130kph is too strictly enforced.

The GT4 doesn't have cruise control to keep it from doing the speed it so badly wants to do. Plus, the gear whine and drubbing of the exhaust gradually get to you. So these aren't relaxing hours as we pass Metz and head on north-west. Sometime deep in the small hours, photographer Rowan has a bright idea: let's go see the historic Grand Prix pits near Reims.

I've never been, though I'm pessimistic we'll see much in the dead of night. But it's a full moon, so worth a try.

You come off the motorway just south of the city, and there, by Gueux on a dead-straight D-road, they loom up at you. A huge, empty grandstand one side of the road, the pit boxes and tower on the other, all kept painted in period advertising for tyre and oil and spark-plug companies, many of them long deceased. These are scary-quick roads: the last French GP here, in 1966, was won by Jack Brabham in a car of his own making at a 137mph average.

At a deserted 3am in the cold hard lunar rays, the silence broken only by the distant autoroute and the cooling ticks of our Porsche, the ghosts of those heroes swirl benignly around. They surely approve of our manic little yellow car.

Rowan is driving now, and I drift to sleep, lulled by the apparent stasis of engine hum behind, darkness to the side, hypnotically pinging lane markers fading into the forward distance. Some time later, I wake, in a mental and actual fog, as he stops for fuel. A thick mist is blanketing the plains of Picardy, and we're reduced to 50mph or so.

I drive again, peering into indistinct mercury-grey. It's a struggle, not helped by the taunting, haunting moon hanging clearly above, so shallow is the stratum of mist. But the darkest hour really is just before the dawn: to the east, the subtle indigo watercolours of first light bring me just enough energy to take us to the Tunnel.

Is it possible to sleep in a fixed-back racing seat? Absolutely. The moment the train wheels start rolling, my eyelids clap shut like guillotines.

At the other end, the Porsche and its driver emerge blinking into a beautiful gauzy Kent morning. I've been wondering how its suspension will cope with the bumps of an English B-road, and whether its tyres will, as per usual with hot Porsches, kick up a racket on our coarse-surface motorways. They sure do.

Up the ridged concrete section of the M20, the noise is like being stuck inside a filing cabinet in a jet-wash. Conversation makes me hoarse. Engine-off in the Tunnel, I'd noticed the clock actually does tick. In no way is it, at 60mph, the loudest noise in the GT4. I turn off into the countryside, craving a fix of Cayman dynamics.

Looking at those slammed wheelarches, you'd think they'd rule out any sensible vertical wheel travel. Yet here's a curious and wonderful thing: give the suspension some work to do, and work it does. It takes the edges off big bumps and allows the body to breathe a bit. You're not uncomfortable, and mid-corner bumps can't put it off.

Adaptive dampers and transmission mounts do their bit too. As often happens with supercar suspensions, the hardness is all in your mind. It's surprisingly fluent.

But now the real test of this chassis. We roll up at the Dunsfold gates a minute after they open. I'd claim, in all modesty, that this was Porsche levels of precision timing given I've crossed three countries and a seaway.

Even after a scant half-lap at warm-up speeds, the GT4 is making itself entirely at home. A few quicker laps show it to be shockingly good.

Where do I start? At the start, I guess. Mid-engined weight distribution and 295-section tyres dropkick it off the line. Its intimate feel explains how Willson's off-camber section wants to roll most cars' tails loose, yet the GT4 itself remains far too composed to do anything of the sort.

As the front wheels load up for the first part of Chicago, the little steering wheel posts me fulsome love notes. Grip through the apex is colossal and so's the security as it blasts out. Through the gears, the engine's willingness and potency bring up Hammerhead in very short order, but there's no need to brake till it's filling the 'screen because the ceramics will happily deform your ribcage.

It does ask for a little patience in the tight first part of the Hammerhead - a McLaren's brake-steer device reduces understeer to zero, a state of grace the GT4 doesn't quite attain.

But, back on the throttle, I'm vastly reassured by the brilliant adaptive damping as it summarily despatches that upsetting bump after the apex. Natural aspiration's instant power delivery makes a lovely job of holding things together on that long exit. A short wheelbase means this isn't a car for easy, long, big, sideways smoking, but the transparency and exactness of all its answers mean you're having huge fun at subtle angles.

Next up, however bold I try to be for the ridiculously fast Follow Through, downforce tells me I've wimped it. And then at Second to Last, which I never get right, its forgiveness is the gift that keeps on giving.

I pilfer more laps than I should, until the 12-hour rule is breached. Porsche Motorsport has built something truly special here, even among the epic line of cars it's built before. I don't like the parent company's sales tactic, mind: they were still officially denying the car would ever exist weeks after their dealers had sold them all out. So you can't have one; the £64,451 price means nothing.

But let's imagine it did. This would be a bargain. A mid-engined supercar, but less. In a good way. Its body is smaller and handier, and its shape more familiar, so less ostentatious. Its engine is just as exciting, but its lower power hands you the joy of extending it more. Choose a great car four times this price: the GT4 is its distillate. Its every move gets right to the point. And to the depths of my being.