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A special-series Cayman with the presence, rawness, drama and pace to mix it with the very best Rennsport Porsches there have ever been

This new ultimate Porsche Cayman has been coming for 17 years; although, as some have held, it was never coming at all.

Back in 2005, just as the motoring world realised how much handling potential was locked up in the brilliant mid-engined chassis of this two-seat sports coupé, some wondered whether, if given enough power and dynamic purpose, this car might even go on to eclipse the company’s GT-department poster boy for outright driver appeal: the all-conquering Porsche 911 GT3. Others ventured that Porsche’s product strategy needs must exclude that eventuality by simply preventing such a Cayman derivative from ever being signed off.

Above 7500rpm, the GT4 RS makes a noise that can’t fail to inspire expletive exclamation. If you thought this engine sounded good in the back of a 911 GT3, imagine sharing an oxygen chamber with it.

But, thanks to the vision of one of Porsche’s more colourful senior executives of recent years and the subsequent commitment and skill of his various cohorts and deputies, the Cayman GT4 RS was signed off, and it’s coming to the UK market this spring.

Initially championed by former Porsche head of R&D Wolfgang Hatz (almost as a parting gift before he became implicated in the Dieselgate emissions-cheating controversy), this car was the simplest of conceptions. What would happen if you put the epic, high-revving flat six from the 911 GT3 into a Cayman? Could you even manage to? And would you make a saleable product with sound business credentials if you did?

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Well, they have managed to. And yes, there are plenty of customers who’d buy one - even for a lowish six-figure sum - because they’ve been battering down the doors of their local Porsche dealers asking for such a car for years.

As to exactly what kind of sports car would result, it’s one of the most magnificently raw and spine-tinglingly special kind that’s made anywhere in the world right now, and offered at any price you care to compare, actually. The GT4 RS has a dynamic flavour unlike any other Cayman: it has first-order pace and a wicked sense of purpose, too, and a simply spectacular audible character that I’d go so far as to say would probably stand comparison with the greatest performance engines that have ever been built.

Does it eclipse even the mighty 911 GT3? In some respects, I think so - as much as that’s a pretty academic comparison. A GT3 puts more rubber on the road, and has a slightly more specialised driveline specification, so it’s quicker around a lap of the Nordschleife and more composed at very high speeds. But a GT3 doesn’t sound as good as this car, believe it or not, and it doesn’t handle with the same mid-engined poise and purity of the GT4 RS, either. The new mega-Cayman is a better car in some ways. The prophecy has come true, sort of; not that the GT3’s in any danger whatsoever as a result.

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Even more so than the 911 GT3, the Cayman GT4 RS feels deliciously over-endowed for firepower – well capable of putting more torque into its driven rear wheels than they can transmit to the road despite being the first car of its particular breed to wear Michelin’s very stickiest road-legal Cup 2 R tyres. Some fast Caymans have approached a similar feel over the years, but none other has felt like such an unabashed, tyre-smoking hot rod.

Accomplishing that transformation from a technical standpoint first meant finding a way to swap the existing GT4’s 414bhp 4.0-litre flat six for the 992-generation GT3’s 493bhp one; and they’re entirely different engines. Being effectively spun through 180 degrees around the Porsche’s rear axle, the incoming motor needed all-new induction and exhaust systems, and a relocated dry sump lubrication system, to make the switch work. 

Being necessarily much longer than the one in the 911 GT3, the new exhaust in the GT4 RS has a pair of rear half shafts to bend its way around on its way to the rear silencers. Producing more back pressure than the one in the equivalent 992 as a result, that exhaust system is chiefly responsible for the GT4 RS’s very slight relative deficits on peak power and torque compared with its GT3-badged contemporary.

“People can believe that we’ve deliberately detuned the engine in order to keep this car in its place if they want to,” says Porsche GT department boss Andreas Preuninger, “but it’s not true. This is a GT3 engine giving everything it’s got, revving to 9000rpm, and packaged in the mid-engined car just as well as we could do it. Believe me: it’s not holding anything back.”

Boy, don’t you know it. Part of the reason why is because the engine breathes unlike one in any other Cayman: not through its flank air intakes, but through an all-new cold air induction system with intakes positioned just a few inches behind the heads of its cabin occupants, where the rear quarter-light side windows might otherwise have been. These intakes feed a carbonfibre air box that sits on the top of the mid-mounted engine - within the passenger compartment. And the whole induction system creates the GT4 RS’s unique and spectacular engine note: one of a pure, pulsing, razor-sharp combustion howl and a convulsing, detailed sort of induction hammer the likes of which this tester has only heard before on classic track cars with open-trumpeted carburettors - and even then not to the same intoxicating effect.

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From within the cabin, at the very least, the Cayman GT4 RS makes the kind of noise that you simply can’t believe can be signed off on a road-legal car in 2022. Evidently, development bosses Preuninger and Frank Walliser didn’t believe it would be, either, which is why they kept their prototypes hidden away during key stages of the car’s development from certain highly placed decision makers at Porsche, who might have otherwise have insisted that incredible howl be dialled down.

“We did a lot to filter out harshness from the engine noise,” says Walliser, “like better securing the whole system to the chassis and damping down the resonances using foam liners for the induction tracts. Originally, this engine sounded very harsh – like a chainsaw cutting its way between your ears, some said. Now it’s got plenty of bite, but not too much.”

Downstream of all that noise, the GT4 RS’s 493bhp finds its way to the road via a short-ratio PDK paddle-shift automatic gearbox (the same one used on the 991v2-gen Porsche 911 GT3 RS) and a passive limited-slip differential. For axles, it sticks with strut-type suspension front and rear, but these are ball-jointed to the chassis and are  closely related in places to the hardware used on other last-generation, GT-department 911 track specials. 

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Compared with the regular GT4, the GT4 RS’s spring rates have jumped by 66% on the front axle and 40% at the rear, but since the GT4 RS’s axle tracks are wider than the GT4’s anyway (6mm front, 8mm rear), the gains in effective spring rate are less. The car has special PASM dampers and adjustable anti-roll bars, and its wheel geometry, too, can be adjusted for both camber and toe angle. Uprated steel brakes and centre-lock forged aluminium wheels come as standard, Extra-lightweight magnesium rims and lightweight carbon-ceramic brakes are optional.

Not that you need to know any of that to realise that this is a proper GT Porsche, because it’s got aerodynamic aggression to spare. Weight-saving carbonfibre-polymer bodywork comes as standard for the bonnet and front wings, which between them also duct air into and away from the front brakes via the NACA ducts and hot air outlets adjacent to the front arches. The swan neck rear wing on the car’s rump is borrowed straight from the GT3 and, along with the front splitter, it’s adjustable to create up to 25% more downforce than the GT4 manages. 

The GT4 RS uses lightweight glazing and interior door panels and carpets, too, and weighs in at 1415kg: some 35kg lighter than an equivalent Cayman GT4 PDK - and that’s only the official homologation figure. Put optional carbon brakes and magnesium wheels on your car, delete the standard-fit infotainment and audio system, and you’ll very likely end up with a GT4 RS that weighs less than 1400kg in running order, and that’s accounting for the optional magnesium roll cage if you want it. The last fast 911 that weighed less was the revered 997 GT3 RS 4.0 of 2011, which, incidentally, also made 493bhp.

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On road or track, this is a seriously fast car, needless to say. Its short-ratio gearbox works supremely well with that sabre-edged flat six and makes the car zap through the gears and out of the corners really urgently, with none of the heavy-legged feel of the Porsche Cayman GT4 or the GTS 4.0. The GT4 RS needs a little winding up, just like a GT3, but at high crank speeds, it feels eye-poppingly savage. Allowing for the audible theatrics, full throttle above 6500rpm is an almost religious experience - and it’s one you might well want to enjoy through earplugs, if not through a racing helmet, on a track day.

The car’s body control is supremely good on circuit, but its ride is surprisingly little compromised on all but the very worst-surfaced roads – something which, after the hardcore 992 GT3, ought to come as good news. This Cayman doesn’t bustle and jiggle you around, or physically impose itself on you like some hardcore specials can. The steering retains that beautifully linear pace, and while it isn’t testingly heavy, it communicates really faithfully. 

The suspension settings trade just a little of the standard Cayman’s readiness to roll and rotate underneath you on a balanced throttle for greater mid-corner stability at the limit of grip, and a much greater appetite for carrying speed. So much you’d expect - but it’s not a punitive trade. Just a shade of the standard Cayman’s celebrated on-the-limit handling tameness has been sacrificed, too. The GT4 RS is a slightly more challenging car to drive as you find the margins of its considerable adhesion than its range-mates are, surrendering its hold on dry Tarmac a little less progressively if you turn off its electronic aids. It’s still so naturally poised and so enticingly adjustable, though – no pussycat but no bear trap, either; just a fascinating mid-engined chassis to fully decode.

Any Cayman with a six-figure price to justify would need to be special, and yet the GT4 RS is so wonderfully raw, so extraordinarily dramatic and so superbly rewarding to drive as to melt away every rational reservation you might have about it. Even Weissach’s very own engineers characterise this car as a sort of teenage wild child, a bright-burning, long-return comet of a car whose like doesn’t come along often, but that lives long in the memory when it does.

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The funny thing is you could get a surprising amount of use out of a GT4 RS if you so chose, which flies in the face of that character definition somewhat and isn’t what we’re used to writing about Rennsport Porsches. It’s still a Cayman after all. But if it were mine, I wouldn’t take it on errands, or wrap it in cotton wool. I’d spend every moment I could on track, trying to make myself worthy of it - and I’d delight in every deafening second.