Tested: The RML GT Hypercar Is Absolutely Bonkers yet Surprisingly Civil

Before we talk about what the GT Hypercar is, it’s helpful to know what RML is. RML Group (originally Ray Mallock Ltd., named for the British racing driver who founded it) is a white-label U.K. engineering and racing outfit. Basically, RML does the engineering of some cool stuff for other automakers but doesn’t take any credit. Creations RML can talk about contributing to include the McLaren Senna GTR, Saleen S7, and the Nissan Juke R.

This creates a challenge at times for RML, and others like it, beyond forgoing the ego stroke of everyone knowing what it has done. Indeed, a recurring problem for such white-label engineering is that it’s tricky to show off your portfolio to prospective partners. As company CEO Paul Dickinson told us, “I can’t go to Jaguar and show them what we did for Aston Martin.” So RML from time to time makes (or, in this case, remakes) its own road cars.

The GT Hypercar—GTH, more familiarly—is RML’s 39th such effort, and that’s precisely the number of customer examples it will produce. The car you see here is No. 6, and as one of the first 10, it’s designated as a 40th Anniversary edition. RML was founded in 1984, and the GTH was conceived at Pebble Beach in 2024; the first customer car was delivered 14 months later, a blink of an eye for a development timeline such as this one.

See All 50 Photos50

What Is It?

The GTH begins as a Porsche 911 Turbo S from the previous 992.1 (2021–24) generation, chosen purposely because it was the latest non-hybrid version. If you’re an interested customer—and at the time of writing, there are a few slots left—you find yourself a nice Turbo S (it’ll set you back around $250,000), ship it to RML in the U.K. along with £520,000 (about $700,000 at today’s exchange rate; RML does not accept checks, but it might take cheques), and what you see here on these pages is what RML will ship back (in your own choice of colors, of course). With options, you’re likely in for more than a million, but that’s still a bargain compared to RML’s Ferrari 250 SWB, a car whose base price registered $1.6 million—and that was four years ago.

What do you get for a million bucks? The transformation includes a new carbon-fiber body, formed using computational fluid dynamics and styled as a what-if exercise. Specifically, what would Porsche have done if today’s Le Mans Hypercar prototype racing class existed in the 1990s? The object of the build was to create an “ultimate GT” that melded the characteristics of the Turbo S and the GT3 RS, for a concoction that is more track-oriented than the former and more comfortable on-road than the latter.

You don’t need to be a diehard Porsche fanatic to see the resemblance to Porsche racers across the decades, so we’ll leave that bit to your own imagination and stick to the facts. The GTH’s body shape is all about airflow. Air that enters the outer portions of the front bumper goes through the radiators and is channeled out and along the car’s sides before reaching the rear fender intakes. Air at the center comes up through and over the hood and windshield, where it meets a new rooftop scoop that feeds the engine intake and, further along the now-rear-windowless roofline, intakes for the intercoolers.

See All 50 Photos50

We Like Its Style

Stand behind the GTH to see what we think is the coolest element: the “car-in-a-car,” where the tail of what was once a 911 Turbo S appears to poke out of its new exoskeleton. That’s an illusion; the rear fascia, like the rest of the skin, is a carbon-fiber re-creation, but the 911’s underlying body structure—the Porsche safety cage—remains intact. So, too, do the windshield, side glass, and inner door structure. RML specifically wanted to keep the original weatherstripping, the best way to keep the doors sealed up. Quality was a major factor in the overall design; it is, after all, a good engineering company’s calling card, so a successful project can’t come across in any way like something a bunch of maniacs built in a backyard.

We must mention the updated adjustable aerodynamic hardware, which includes electric actuation for the chin spoiler and rear wing. Even before the driver deploys the aero bits, RML says the GTH develops nearly three times as much downforce as a stock Turbo S; setting the aero to Track mode increases that by half again, and another setting shifts the movable section of the rear spoiler to instantly reduce drag by 21 percent.

See All 50 Photos50

The car has a more solid stance than the stock 911, and that’s no illusion. The track is 4.0 inches wider than stock, and the wheelbase is an inch longer. No spacers are used here; RML engineered a whole new suspension that attaches to the original mounting points. Brakes, always a Porsche strong point, are largely unchanged.

You probably expect all the carbon fiber to lower the weight, but the overall greater size and added hardware made up for the balance. At 3,759 pounds—the rear axle supports 60 percent of that total—the GTH seen here is 131 pounds heavier than the 2021 992.1 Turbo S we tested when it first came out.

Inside, the cabin looks mostly stock; as Dickinson explained, most 911 owners are happy with the cabin. GTH No. 6 sports trim and material upgrades and optional shell seats, which can be used with either a racing harness or the stock seat belts. The rear seat is gone, along with the rear window; a roll cage replaces the former, and a camera does the work of the latter.

One of the coolest alterations is on the steering wheel, which has four control dials instead of the stock single dial. The top-right dial serves its original Porsche purpose of setting the powertrain mode. The other three, in left-to-right order, control aerodynamics, ride height, and damper settings. They look, move, and feel exactly like the original Porsche dials. RML also added magnets to the shift paddles to give them a more positive feel with every pull.

See All 50 Photos50

Powertrain Details

Finally, we must talk about the engine. (You didn’t think RML would leave that alone, did you?) The company subcontracts this to Lichfield Motors, which upgrades the 3.7’s intake, exhaust, turbos, intercoolers, and software, raising output from 640 hp and 590 lb-ft of torque to 920 hp and 738 lb-ft. The eight-speed PDK twin-clutch auto can handle the extra twist and remains largely unchanged.

This car, on paper and by sight, should be scary, but it totally is not. As wild as the exterior is, the experience of getting going in the GT Hypercar is quite Porsche-like. Well, perhaps other than the fact No. 6’s optional shell seats are somewhat of a pain to get in and out of. GTH buyers can get a more ordinary seat, but this version was built for longtime NTT IndyCar Series racer and car collector/entrepreneur Graham Rahal, whose Zionsville, Indiana–based company, Graham Rahal Performance, is the GTH’s official U.S. importer and retailer. That said, once you’re in the seat, it’s like sitting in a factory-built Porsche. Turn the not-quite-key on the left, and the 3.7 fires with a raucous blat then settles into a smooth idle. You’d never guess the engine is capable of making nearly half again its original rating.

In Normal mode, the flat-six develops a mere 760 hp; the exhaust stays baffled, and the transmission shifts early—and the thrills are still sky-high. It’s no surprise the GTH takes off like, well, like a proper hypercar, with fighter-jet thrust and the deep roar of a tuned Porsche engine. Turning the powertrain dial to Sport opens the exhaust and the full 920 hp, while Sport Plus sharpens throttle and transmission response on top of that. You can use the paddle shifters, but what’s the point? With this much capability under your foot, acceleration is nearly instantaneous no matter what gear you’re in.

See All 50 Photos50

Putting It to the Test

We wondered, though: Would it beat the donor car’s numbers? RML let us hook up our timing gear for what we believe is the first independent, outside-the-company instrumented test of a GTH. We did have some arguments with the electronics and could not always disable stability control, so we made some acceleration runs with the nannies watching. RML assured us this will be addressed in an over-the-air update that was not yet applied to No. 6.

The company leaves the factory Porsche launch control intact, so that’s what we used, and its M.O. is to ride the hell out of the clutch for what seems like quite some time before blasting the power. The GTH didn’t necessarily feel as willing to hook up as the stock Turbo S, which could explain our 0–60 time of 2.4 seconds, 0.1 second slower than the ’21 Turbo S. But the GTH matched the stock Turbo S’ 10.3-second quarter-mile time, though its 131.5 mph trap speed trailed the original car’s by 0.8 mph. On the other hand, the GTH scrubbed speed better, stopping from 60 mph in an excellent 96 feet, 1 foot shorter than the 992.1 Turbo S.

See All 50 Photos50

As Rahal reminded us before we even drove the car, however, the GTH may act much like a Turbo S in a straight line, but when we hit the curves and our figure-eight handling course, it showed itself to be a completely different car, and that’s far more of its point rather than trying to set acceleration records.

“Absolutely bonkers,” said associate road test editor Erick Ayapana, who performs much of our track testing and who ran the GTH through the MotorTrend regimen. “The view from the driver’s seat is pretty much 911 Turbo S, but the driving experience is far from it.” To his point, while the chassis’ initial turn-in did not feel quite as quick, largely owing to the GTH’s larger dimensions, it’s also much more slidey, huge fun, and most important, very controllable. You can trail brake and run clean, but it’s so much more amusing to be aggressive and attack the corners sideways. We just kept grinning about the experience.

See All 50 Photos50

We also want to extoll the lack of surprises on the skidpad, where the GTH pulled 1.16 lateral g, well more than the stock Turbo S’ 1.10 g. We discovered that you always know exactly when you’re at the grip limits, and when the tires let go, they do so in a smooth and predictable way. While the ride felt overly firm on public roads—more on that in a tick—we found it surprisingly and satisfyingly compliant on the track, despite lowering it to its lowest ride height and adjusting the damper stiffness for the best possible runs.

Numbers, please: The RML GTH circled our figure eight in 22.2 seconds, 0.3 second quicker than the Turbo S and, more significant, at an average grip of 1.03 g. We’ve seen faster times, but few cars top 1.00 g of aggregate grip on the figure eight. What our handling tests and the speeds they are performed at do leave on the table is the advantage of all that extra downforce at triple-digit speeds, something we didn’t have the opportunity to test on a high-speed road course this time around.

See All 50 Photos50

What About the Real World?

Out on public roads, though, the RML feels more like a racer than a tourer. The ride, while not as punishing as the GT3 RS’, is still noticeably hard on bumpy pavement, and the car is noisy even with the exhaust in Quiet mode. You hear plenty of pebbles plinking up against the expensive bodywork, too. That said, we appreciate the adjustable ride height, which allows the GTH to deal with railroad tracks and driveways without incurring damage; the car has a nose lift system, accessible via the ride-height dial, which keeps the front end raised when driving slower than 40 mph. Dickinson recommended keeping it activated any time we were below that speed, and we found doing so had no greatly adverse effect on ride quality or appearance.

On a smooth road—or even a not-too-smooth one—you can drop the height, kick out the spoilers, punch up the powertrain, and let ’er rip, but the problem, if there is one, with all these 900-hp cars in real life is that you’re always seconds away from a lot of points on your license. “Ultimate GT” might be a bit of a stretch, as we imagine most of the lucky 39 owners will prefer their Ferrari 812 or such for long-distance travel, but this is an honest-to-goodness track superstar you can drive, rather than trailer, to the racetrack.

Final Thoughts

What impressed us most about the GTH is—well, hell, how can we pick one thing? The numbers are amazing, the styling is the business, and the performance is as serious as it is exhilarating. What really stands out, though, is how approachable and refined the car is. A 920-hp hypercar makeover of one of the top-end 911s could easily be scary and troublesome, but this is a relaxing car to drive, and it feels like something that could have rolled off Porsche’s Zuffenhausen assembly line. And that is exactly what RML was going for. So yeah, we’re sold—next time a high-end automaker needs help from someone to engineer a super performance or hypercar, even if it all needs to remain hush hush, we recommend it give RML a call.