When the current 911 GT3 RS landed, it appeared Porsche - Zuffenhausen, the mothership - had finally pinned motorsport satellite Manthey into a development dead end.

This mattered because tiny Manthey's ability to turn a showroom-spec GT-division 911 into something even more special had always quietly frustrated Porsche, and especially division leader Andy Preuninger. Manthey would apply racing tricks that the factory, snared by endless homologation red tape, couldn't. Mightier wings, more aggressive geometries, belly-scraping ride heights: Porsche's RS people had the desire and the know-how but only Manthey, with its cottage status, could actually sell you anything. And boy did it reap the reputational rewards.

During the gestation of the 992-generation GT3 RS, something clearly snapped at Porsche. Test mules wore wings so huge that many assumed they were assessing aero for the Le Mans-bound 911 RSR. When the car was eventually revealed, we discovered that it had sacrificed its frunk in favour of a colossal motorsport-style central radiator, and that even its wishbones were sculpted to generate downforce. It was mutated in a way that made us wonder if its creators had lost touch with reality, but this was only the mark of a job well done. Where could Manthey possibly now take the package? Preuninger's scorched-earth engineering policy had left no avenues.

Or so we naively thought. Before us in the pits at Silverstone, radiating menace, is Nürburgring-based Manthey's take on the 992-era GT3 RS. It is a 3RS, clearly, just not a normal one. The body is slammed to the deck and the wing wears endplates that could shutter the windows of a Georgian town house. It has roof vanes to direct messy hot air escaping the central front radiator sideways, lest it interfere with the DRS rear wing. The front splitter juts out so far that it requires supports. There are canards, aero discs for the rear wheels, plus a shark fin and the mother of all diffusers, all wrought in carbonfibre. The result is downforce increased from 860kg at 175mph in the regular 3RS to more than one metric tonne in the Manthey, with no additional penalty in drag.

And those are just the bits you can see. Underneath the skin, gone are the donor car's Bilstein dampers, replaced by KW units with custom springing and valving. Manthey cars historically used manually adjustable dampers but this time the hardware is plumbed into Porsche's finickety new PASM system for altering bump and rebound on each axle via the steering wheel. One suspects the tuning of this system has not been the work of a moment. There are also braided brake lines and sticky Michelin Pilot Cup 2 R tyres that can buy you 10 seconds at the 'Ring.

None of it comes cheap. At £99,999, the opportunity cost is a brand-new 911 Carrera. Give that a moment to sink in. Equally, there is now added convenience. Where previously you needed to get in touch with Manthey, now you simply tick a box on the Porsche configurator.

And that, everyone, is the really big twist. The 992 3RS represents the first time Manthey's kits have been brought in from the cold, after Porsche's acquisition of a 51% stake in the company in 2013. It's taken more than a decade to get to this point but the result is the world's wildest optional extra. It doesn't void the warranty and is even fully homologated, which goes some way to explaining the eye-watering price.

Today, we embark on a voyage of discovery, to see how all that downforce and Manthey's other tweaks affect the lap time of the amateur driver. In November 2024, I came to Silverstone with the regular 3RS, exploring its massive potential and the benefits of that complex new PASM set-up. The quickest white-knuckle lap around the grand prix layout and therefore our benchmark time was 2min 13.10sec, the car shedding speed as though it had snagged an arresting wire and clinging on through fast bends like Copse with a demented zeal. It pulled nearly 1.8 in lateral g at points, which for a machine with numberplates and CarPlay was and remains an outrageous feat.

Exactly a year later, circumstances favour our comparison. At 12deg C, ambient temperature is identical. So too is the dampish-ness of the track in the morning, which by 3pm will be dry. Critically, and as per our request, this particular Manthey GT3 RS is shod with regular Michelin Cup 2 tyres, just as the standard GT3 RS was.

On the move, the difference between regular GT3 RS and the Manthey is subtle but obvious in the way you would notice running your fingertips from 120-grit sandpaper to 80. During sighting laps, I'm surprised at how much fizz there is in the feedback through palm and thigh. The car is more granular, and you hear the rose-jointed suspension clinking away, which adds its own theatre. Because of the shark fin, behind you is only darkness and roll-cage. Here we have a rawer, twitchier, altogether more serious personality. The thing is also pretty cantankerous on the road, the regular 3RS being far sweeter company on long drives.

But the track is what matters. A year is a long time but so rich are the synaptic memories of driving the normal RS that I recognise the Manthey car's superior ability to get its snout into tighter, low-speed bends. At the other end of the spectrum, the new brake lines, and perhaps that lower ride, contrive to make high-speed braking monumental mashings of the pedal made suicidally late feel even more daring. Silverstone is the ideal place for exploring the limits of grip in a car like this, with triple-figure transitions and corners that never end.

Subjectively, though, it's a close-run thing. The ability of both cars to contain the yaw impulse of their heavy tails during trail-braking, without killing rotation entirely, is something special. It's just that the Manthey will tolerate more ambitious turn-in, its ability to inspire confidence being just a little greater. The normal 3RS feels like an amped-up road car, while the Manthey sticks like a declassified racing car.

In the end, it puts in a 2min 15sec lap 1.95sec quicker. Checking over the telemetry, the Manthey's advantage is in its ability to carry a couple of extra miles per hour on the exit kerbs of faster bends like Farm, and carry more speed into the rollercoaster Maggotts-Becketts sequence. Outright braking distances aren't notably shorter, interestingly.

Clearly the Manthey allows you to draw more speed to the apex. During huge sweeping bends, where your senses are on red alert for the early signs of grip eking away at either axle, it also simply holds on a little longer. And perhaps, for the amateur, it just encourages you to try wilder things, more of the time.

Would a professional have squeezed more or less time from the kit? The sliver of extra confidence the Manthey 3RS seems to give you, so useful to the amateur, would matter to them less. On the other hand, a pro driving on the true limit of adhesion would maximise the Manthey's downforce advantage everywhere. Next time round we'll have to give Jörg Bergmeister a call, but today, two seconds on a full grand prix circuit, in similar conditions and on the same rubber? That counts as daylight. Just over £50k per second is a mad premium, admittedly, and a better example of diminishing returns you won't find.

I'm sure Manthey, pressing its spectacles up onto the bridge of its nose, would argue that you're getting a different machine from the regular car in subjective terms, not just a quicker one. I'd absolutely agree. In the world of official factory efforts, you're also getting no less than the most extreme track-day 911 in history, which for plenty of people will feel priceless. 

One-tonne club

Being able to claim more than 1000kg of downforce is no mean feat for a street-legal machine. Very few cars have ever managed it and they're mostly seven-figure special editions, which makes the Manthey a total bargain in this one specific metric.

Although not a member of the one-tonne club, one of the most famous of this ilk is the Caparo T1 - the 600kg canopied single-seater with an Indycar V8 and insectoid looks. In 2007 it made 875kg and we lost our minds over the fact that you could drive it to the shops yet also drive upside down along the ceiling of a tunnel - in theory. 

The T1 was a precursor to some of the cars in the one-tonne club today, taking prototype racing car architecture and offering it with a V5: look at the Aston Martin Valkyrie and the Al-optimised Czinger 21C, not to mention the Mercedes-AMG One. As for the most economical way to have 1000kg and numberplates? Look no further than the Ultima RS, yours for less than £200k.

Thanks to Silverstone - the UK’s only Formula 1 circuit – for providing access to the Grand Prix layout for this feature. Whether you’re a passionate enthusiast or a seasoned racer, take your car to the track, everyone can experience the thrill of Silverstone’s iconic circuit. www.silverstone.co.uk/track-and-testing/car-track-days