Porsche 911 GT3 RS v Manthey GT3 RS: How much quicker can Manthey make the ultimate 911?

You doubtless know the 992 GT3 RS Manthey kit by now, so we won’t spend too long running through what distinguishes a car such equipped from the standard 911 GT3 RS. It’s quicker to cover what hasn’t been touched: the engine and gearbox. In truth there’s very little juice left to squeeze from the 4-litre flat-six, which is already something of a masterpiece. 

An independent tuner might decide to bore it out by a few hundred cc and lose some of the restrictive emissions kit, but being part of Porsche means whatever Manthey does must remain within the series production car’s homologation approval. So 518bhp and 343lb ft it is.

The powertrain may be off-limits but pretty much everything else is fair game. The wild aero package brings total downforce to a little over 1000kg. That’s a 20-ish per cent gain with no increase in drag. The suspension retains the semi-active PASM tech but has been completely re-rated by Manthey and runs new controllers for quicker response and more precise control. There are also new brake pads, braided lines and fluid for a firmer pedal and absolute consistency.

Driving the standard, £192,600 992.1 GT3 RS requires some recalibration compared to pretty much any other series production car, but the Manthey RS presents an even greater challenge. Where most cars at this level have a surfeit of grunt over grip, both stock and Marvel-spec Manthey RS are the other way round, their emphasis firmly on commitment and precision under braking and corner entry rather than balancing traction on the way out. 

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Finding the limits of the standard car is hard enough; extracting the best from Manthey’s machine requires a further leap of faith. Timed runs in the standard car help settle nerves and achieve the needed mental reset. It’s a truly scintillating machine; quite unlike any other street car in the way it feels and performs. 

It absolutely flies during our timed laps on a dry circuit, achieving a best of 1:11.2, which is 0.8sec faster than we achieved in 2024 (evo 328) on the same Michelin Pilot Sport Cup 2 R tyres. It’s hard to imagine how you could make this car go any quicker through corner speed alone.

To help get dialled in to the Manthey RS, we first do a timed run with a new set of Cup 2s rather than the more extreme 2 Rs. It’s a worthwhile exercise. Not least because the resulting best of 1.11:10 eclipses the stock RS time by a whisker (8/100ths to be precise). More valuable is knowing that the additional downforce, needle-sharp front-end, resolutely planted rear-end and bulletproof brakes match the best efforts of a standard RS shod with Michelin’s grippiest road-legal rubber, apparently without being any trickier to drive.

Pressure ramps up when we swap the Manthey car onto Cup 2 Rs, which only give their absolute best for one or maybe two attacking laps before stabilising a few tenths off their maximum performance. Manthey’s technicians – who have flown in from Germany to ensure the car is in tip-top shape – have wrapped them in warmers, but this means a bit of F1-style tyre management will be required as I leave the pits, the out lap needing to be just quick enough to maintain the heat but not so quick as to waste any of that peak performance.

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If this all sounds a bit much for an admittedly highly track-optimised street car, then you’d be right. But it’s indicative of how seriously Manthey takes this test. It’s also appropriate for a car that wouldn’t look out of place on a World Endurance Championship grid. Make no mistake, the particular thrill of driving this car is rooted in knowing it thrives on commitment and focus.

After the anticipation and subsequent learnings of the preliminary timed laps on Cups 2s, the fast laps on Rs are even more special. The directness of the steering is now even more intense, with endless bite and immediate response to the smallest of inputs. It’s this confidence in the front-end that gives you the foundation upon which to build the lap, braking even deeper and stealing yourself to come off the brakes and roll as much speed as possible into the apex before trying to be just as decisive when you get back on the power.

Turn 1 is always tricky as it tempts you to turn in too early, but knowing the nose will stick means you can wait a fraction longer before slicing into this left-hander, then allow the merest moment to let it settle before chasing the throttle to carry as much speed as possible into the compressed braking area for the heavily cambered hairpin right that follows. 

It’s very easy to outbrake yourself here as the approach looks so tempting, but the Manthey RS finds so much to lean on, both braking in a straight line and while turning down into the apex. It’s a fabulous feeling, especially if you manage to blend braking, turn-in, throttle and corner-exit phases into one seamless flow. You know you’ve had a good exit when you upshift a few metres early on the run to the subsequent Church right – the fastest and most crucial corner of the lap.

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You feel the added pace as you try to judge your entry speed, again resisting the urge to turn in too early and fighting the fear of a mid-corner correction and running wide on the exit. You want a car to be perfectly neutral through here; strong initial bite so the nose is pinned, with just the right amount of rear-end stability to let the car rotate while remaining stable. The challenge is being positive with your inputs but keeping them small and tidy. The reward is running hard and fast from apex to exit, a fwarrrp from the corrugated kerb and small puff of dust from the track margin signs that every bit of track has been used. 

Just as in the standard RS it’s then time to hit the DRS button (the third of four shots during the lap) for the long run into the nameless uphill kink. Both cars take it easily flat but the Manthey carries more speed thanks to its faster run through Church. Better, the added downforce means it’s possible to bring it further to the right before the big stop from the highest peak speed on the lap into the slowest corner, Rocket.

Much like the faster turns, the Manthey RS cuts through the tighter corners that bit more cleanly, allowing you to carry small but meaningful gains to the apex then get better drive out onto the straight. Another advantage is increased composure on the few occasions you can take some kerb. 

Manthey’s bespoke controller for the PASM monitors and adjusts the damping of each wheel in real time, with special attention paid to managing vertical wheel movement over sharp impacts. This is especially useful into the awkward downhill left-hand entry to the Corkscrew, where you can run the kerb to straighten your line, and the more aggressive saw-tooth kerb that follows.

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Crossing the line to complete the final flying lap, the Vbox shows a best of 1:09.9, with the other laps within a tenth or three. That’s a 1.3-second improvement over the standard RS around a 1.55-mile lap. I have no doubt that with further laps (and fresh tyres) further improvements could be found. Not huge, but maybe half a second.

At £100k (plus fitting) the Manthey Kit is big money to spend on what by common consent is already one of the greatest road-legal track-honed cars money can buy. And yet when you drive the car it all makes sense. Sharper, more precise, more direct and more consistent, it amplifies the regular car’s capabilities then adds a layer of Manthey magic on top. 

Not everyone will see the point, but for those who do, few cars at any price deliver this kind of experience, one which immerses you in the addictive process of extracting more from yourself to get the most from your car. Perhaps the biggest testament to what the Manthey Kit achieves is the fact that this 500bhp 911 is a tenth of a second faster than Ferrari’s 1000bhp SF90 Assetto Fiorano, and second only to the ultra-specialised single-seater BAC Mono 2.5 in our leaderboard of all-time fastest street-legal cars.

GT3 RS lap times  Anglesey Coastal Circuit  (1.55 miles)