Road and track in a Porsche 911 GT3 Manthey Kit

It probably seems safe to assume that, if you’re in the market for a Manthey Performance Kit to add to a 992.2 GT3, you’ll care about the track showing. That’s the focus of this story, and feel free to skip to Sam’s verdict below for that. But it would be remiss, surely, not to experience the upgraded car on the public highway as well. The standard GT3, after all, is the most complete road and track package on sale; a change that tilts the balance too far towards the circuit could undermine that incredibly broad batted appeal. 

In much the same way that everyone around will notice the Manthey overhaul – this GT3 smoulders with presence, the new spoiler and diffuser unmissable – there’s no doubting the intent onboard. ‘Unapologetic’ probably best describes the GT3 at low speed on its four-way adjustable coilovers, jostling with every surface and borderline restless in truth. Exquisitely damped, of course, but permitting absolutely no slack whatsoever. The ‘Track’ setting, understandably for such a focused Porsche Motorsport car, simply isn’t usable. You wouldn’t think twice about commuting in a GT3; this one, not so much. Those racier pads squeal, the cage creaks, every element of the experience is angrier, more intense. 

The flipside of a more recalcitrant GT3 at low speed is an even more thrilling one with some commitment. Despite the inevitable focus on aero grip and lap times with a Manthey Kit, there’s the feel of a 911 tarmac rally car to this Gotham City GT3, endlessly absorbent and never happier than flitting through direction changes. Traction and grip are epic, the sensations flooding through your body a level above what even a regular car can deliver. There’s something deliciously old school about the experience, a true road racer that’s grumpy when pottering and never happier than when really extended. But it’s difficult, really, to suggest those Manthey enhanced highs are worth enduring the lows for if the GT3 is to remain predominantly a road car. The ordinary version is simply too spectacular to make this sort of compromise worth paying RS money for. Wonder if Sam thought similar… MB

Few road cars with a roof and airbags are quicker out of the box on track than a 992.2 911 GT3, but to Manthey, even Porsche’s current most hardcore atmospheric model is merely a decent starting point from which to create a monster. To evolve the GT3 into something that feels like a Supercup racer with plates, the factory-owned motorsport outfit has developed a suite of aerodynamic and chassis changes that have created a GT3 capable of lapping the Nurburgring Nordschleife in 6:52.98. That’s 3.3 seconds quicker than the time clocked by Porsche’s Weissach Pack 992.2 GT3, in less favourable conditions – and Manthey’s YouTube onboard video confirms that said time required astounding levels of commitment. Everywhere.

And don’t I know it? After just 15 considerably less committed laps behind the wheel of Manthey’s creation on Britain’s fastest track, Thruxton, my torso feels like it’s done an intense core workout and my pupils are more dilated than a student at a Prodigy concert. This thing’s so much quicker than I’d expected – and that’s even after I’ve been given the full run through of mods by the Manthey team.

Admittedly, they don’t expand into the engine bay, as the 4.0 flat-six and PDK gearbox remain in regular GT3 tune, but no inch of the car’s bodywork has been spared influence from Manthey aerodynamic changes. At the front, the splitter has grown by 12mm, which is the maximum engineers could do without having to re-homologate the car as a new model as far as pedestrian safety tests go. More noticeable are front canards on either side of the bumper, which are there to press the nose into the ground at speed, helping to boost downforce at this end by about 30 per cent. But look more closely and you’ll see the splitter is also angled slightly upwards, forcing a higher volume of air under the car.

This air is channeled by deflectors underneath that have grown from a few centimetres on the GT3 to being 1.2 metres long on either side of the Manthey’s floor. They’re not short either, hanging so low off the floor to maximise the airflow to the rear diffuser that Manthey finishes them with wear markers, because they’re designed to bottom out when the car’s fully loaded with downforce. Once they’ve lost 8mm in height, Manthey recommends replacements, but because they’re made of plastic, they’re apparently not that expensive. Anyway, needing new ones will no doubt be a badge of honour; like a biker that needs new kneepads from all that leaning over.

No less of an impact on performance is the fitment of a massive carbon fibre rear diffuser, along with a much-bigger carbon fibre rear wing. While the diffuser makes the most of the air that’s passed under the car with a two-step design pinched from Manthey’s 992.1 GT3 RS parts bin (the 6:45 ‘ring lap of that is also worth watching), the wing, complete with curved endplates to guide air onto the GT3’s Gurney flap, uses its swan neck design to convert airflow into downforce, ensuring the car produces 575kg of the stuff at 183mph. Porsche only quotes a 140kg peak at 124mph for its ‘standard’ GT3, but clearly there are some big gains here. The overall aero balance has shifted forwards compared to the standard car too.

Naturally, the chassis sees significant changes, with a new front spring rate that’s 20 per cent stiffer than the GT3’s, and a rear spring rate that’s actually seven per cent softer. The dampers are obviously much firmer in Track mode, but interestingly, Manthey reckons its softest setting is actually more forgiving on the road (I’ll leave Matt to confirm/contest that), although unlike Porsche’s fully electronically-controlled setup, the Manthey GT3 requires a couple clicks of the damper knobs to change the settings. How very race car. That said, you can use the steering wheel’s Drive Mode dial to change the semi-active rebound settings for both low and high speed corners, so quick trackside changes don’t require you to get the axle stands out.

As for unsprung mass, the centre lock wheels are together 6kg lighter than the GT3’s set, and while they’re 1.4kg heavier than the Weissach pack’s magnesium wheels, they’re also a heck of a lot cheaper too. Well, ‘cheaper’ in a Porsche GT sense; it’s still £9k for the set, but that’s about five grand less than the Weissach rims. You can, if you fancy, go for the mags, but knowing how hard track life can be for a wheel, it’s not surprising the car Manthey brings to Thruxton comes equipped with its tougher alloys. They come wrapped in Michelin Pilot Sport Cup 2 rubber, unless buyers opt for the Cup 2 Rs for maximum organ shifting potential. That’s not just through the bends either but also under braking, because Manthey’s pads offer more friction and track durability than standard.

To help clean up the airflow past the rear wheels, Manthey adds an aero disc to the rims, which adds an unintentional but very welcome Group C 956 vibe to the exterior. Since it ‘laminates’ the airflow around the side of the car, it actually enables some of those aforementioned other aero pieces to work more effectively, thereby contributing to the downforce gains. Manthey said the front doesn’t get these discs because, not surprisingly, it needs the wheels to be uncovered so brake heat can be dispersed. Plus, there’s something cool about a mis-matched wheel setup on a track-focused car, isn’t there?

If you’re wondering, the geometry and ride height of the Manthey setup is actually identical to the regular GT3, partly due to homologation rules but also because it’s said to be close to optimum already, even with the upgrades. There are a few smaller changes elsewhere, including some optional extras, like the tow hooks, which are titanium rods with aluminium hooks, making them light and also strong enough to pull a car out of the kitty litter. Not that there’s much of that at Thruxton. It’s all 130mph corners, grass banks and walls…

You’re eminently aware of that on the sighting laps, because Thruxton is an old school track with exposed furniture (like trees) all within a couple of seconds’ reach if things go wrong at 100mph-plus. A Hermann Tilke track this is not; a pair of chicanes are all that are there to stop this being a 140mph average speed circuit in a Manthey GT3. Or maybe that’d be 150mph average because my recorded POV footage confirms (because I daren’t look away from the track on the actual run) that the speedo shows corner approaches around the back of the track are at over 140, and the car nudges 160 before the braking point into the final chicane. And that’s on the ‘warm up’ tyre, Cup 2s.

Five laps on those confirm that the Manthey upgrades can make a 510hp flat-six and PDK feel quicker because you can get on the power harder and earlier. But the car doesn’t feel as pointy as I’d expected. Instead, it’s bolted down safe. A switch to Cup 2 Rs fixes that. These are basically a cut slick race tyre with road homologation, so they offer race tyre levels of grip, and this feels entirely appropriate in the Manthey.

The steering feel of a GT3 has always been fantastically rich, but with these stiffest of road tyres you can really get to the limits of front axle loading surprisingly quickly. And yet while there’s clearly more grip, the car doesn’t feel inert. Instead, it’s hyper agile. Keep your left foot pressed hard onto the brake pedal and apply steering lock, and the loaded-up Manthey GT3 darts towards an apex with barely believable composure. Dive and body roll is practically non-existent, but the suspension isn’t so rigid that you can’t use Thruxton’s chicane kerbs. The car doesn’t bang over them but instead clips, leaps and lands like a ballerina.

Perhaps not surprisingly, a rear-engined, Cup 2 R-shod creation such as this can handle prodigious amounts of corner exit throttle, so much so that chasing the on-power limit is almost the biggest challenge of the lap. Attacking each corner entry like Jason Plato doing one of his once famous do-or-die BTCC lunges quickly feels quite natural, but once the ESC’s off, following that up with steering lock and full throttle feels risky. Not least because typically if you get things wrong on the back section of Thruxton (especially through the rapid Goodwood and Village bends), you’re heading towards a grass verge at 140mph. But 510hp is no match for the hundreds of kilos of downforce present here; the Manthey clearly has more grip than power. Only in the lower speed corners do occasional kicks of oversteer require flicks of the wrist to gather things up.

You can get silly if you want – match an armful of lock with stabs of on/off throttle inputs and you can have the 4.0-litre behind swinging around like a pendulum. But otherwise, this Manthey is somehow astonishingly fast and wonderfully approachable. Sure, a £56,000 upgrade kit (and the rest, see the specs below) on a GT3 was always going to make something fast, truly rapid, but something that takes a handful of laps to get your head around? That’s much harder to achieve.

For those with the cash, the Manthey upgrade brings a significant boost not just in lap time performance but also driveability, and versus other aftermarket brands, having the Porsche seal of approval and access to Porsche centres for routine servicing is just the icing on the cake. For those who want the maximum in GT3 track performance, the Manthey upgrade is, dare I say it, a no brainer. SS

Engine: 3,996cc, flat-six
Transmission: 7-speed PDK/6-speed manual, rear-wheel drive
Power (hp): 510@8,500rpm
Torque (lb ft): 332@6,250rpm
0-62mph: 3.4 seconds (3.9 manual)
Top speed: 193mph (194mph Touring)
Weight: 1,439kg (DIN, 1,420kg with Weissach/Lightweight)
MPG: 20.5-20.6
CO2: 310-312g/km (WLTP)
Price: £158,200 (as standard; price as tested £280,517 comprising Jet Black Metallic for £1,067, Weissach Package without roll cage for £15,597, Porsche Ceramic Composite Brake (PCCB) with Brake Calipers painted in black for £9,797, Wheels painted in Satin Black for £1,027, Lifting system front axle for £2,701, ISOFIX fastening system for £154, Tinted HD-Matrix LED Main Headlights for £2,562, Exclusive Design Taillights for £462, Club Sport Package £NCO, Front Air Intake Grille with Weissach Package Logo for £1,233, BOSE® Surround Sound System for £1,269, Lightweight sport bucket seats (foldable) for £5,390, Sport Chrono Stopwatch Instrument Dial and digital Tachometer for £462, Aluminium pedals for £298, 911 GT3 Manthey Kit for £56,000, Carbon Set for £12,000, Lightweight Wheel Set Black for £9,160, Tow Straps Black Individual (x2 units) for £668, Racing brake pads for the front axle (PCCB) for £1,295, Racing brake pads for the rear axle (PCCB) for £1,175