Modified 600bhp UK’s most extreme 1998 Jaguar XKR X100

XKR BADCAT  With 600bhp due to a raft of engine modifications, plus an extreme body kit, is Badcat’s upgraded XKR the UK’s most modified X100? We dare to tame the beast to find out.


With 600bhp from a 4.4-litre supercharged V8, plus some aggressive body modifications, is this XKR the most modified X100 in existence? We dare to drive the Badcat to find out. Words Paul Walton and photography Anthony Fraser.

Thank you for not asking about costs,” says Graham Wood, owner of the extraordinary X100 XKR you see here, just before we say goodbye. I had been considering enquiring howmuch the transformation had set him back, but, like asking a lady her age, decided it would be impolite to enquire the size of the figure. Plus, judging by the many bespoke hand-crafted modifications that Graham has designed and had manufactured by small independent engineering specialists, it is obvious it couldn’t have been cheap, yet it has created a totally unique XKR that pushes the model’s boundaries. Incredibly fast, ridiculously loud, and aesthetically outlandish, this is no ordinary Jaguar; this is the Badcat.

Graham has been modifying cars since he was a teenager, so it was obvious he’d do the same with the XKR. He’s the first to admit, though, that he never intended to take it so far, but midway through the transformation he hit on the idea of reaching 600bhp at the flywheel, and every subsequent modification has been in pursuit of that lofty figure, or to tame it. The car started life as a standard XKR 4.0 coupe. Registered in June 1998, it is a very early example. Graham first saw it at a local garage in August 2007, where it was for sale. It was very clean with low mileage, and Jaguar-enthusiast Graham knew he had to have it. “I’d been looking out for a nice car for a while,” he says, “and I’d always loved the X100.”

After driving the car in its standard form for a few weeks, he became acclimatised to the speed. The process to make it faster started not long after.

In late 2007, Graham had a smaller top pulley and a larger bottom pulley fitted.

Along with a Racing Green supplementary ECU upgrade, the changes resulted in 456bhp at the flywheel, as compared to the car’s standard 390fwbhp. The first aesthetical change was swapping the original 20in Paris-style alloys for some deep-dish Ascari Pentas, which it still wears.

Knowing the 4.0-litre had reached its limitations, in July 2008 Graham found and bought a 4.4-litre V8 block from a Range Rover HSE and had it built into a full engine using stronger pistons that were specifically made by German automotive parts manufacturer, Capricorn. So began Graham’s desire to have bespoke parts, rather than simply buying off-the-shelf items.

“I thought if I’m going down the modding trail I’m not going to simply bolton aftermarket items like everyone else,” he declared. “I’m going to do it properly.”

In early 2012, Graham had 4-2-1 stainless headers made to own his own design, which added another 30bhp-40bhp over the original cast iron items. He also designed an under-axle exhaust system, and installed re-worked, ported and polished heads. Later the same year, he contacted Dan Turner at Advanced Motorsport Engineering to fit a stand-alone ECU. After some trial and error, an AEM Series 2 – the same model Derek Pearce uses in his XK8 racing car – was made to work with the 4.4 V8, allowing Dan to map the engine cylinder-by-cylinder, resulting in an astonishing 480fwbhp.

By then, Graham had made contact with marque-specialist and X100-modifying expert Tom Lenthall, who became involved in the car’s development (and still is). It was through one of his contacts that in August 2012 Graham managed to obtain an uprated Eaton supercharger that had been modified for Apex Motorsport’s XKR GT3 racing car – and had never been used; the team had folded when owner Richard Lloyd was killed in a 2008 plane crash. The supercharger gave the V8 another 30bhp at the flywheel. With so much power (now 510fwbhp), Graham’s next priority was to improve engine cooling. Consequently, Tom fitted a larger ‘charger cooler by an American company, RX Performance.

Development of the car might have ended there had it not been for a disaster in July 2016 when Graham was travelling at 150mph down the Lavant Straight during a Goodwood track day and the V8 detonated due to poor fuel pick up, in the process melting five of the eight pistons. Thankfully, the 4.4-litre block was salvageable, and the engine was rebuilt by Classic & Modern Engine Services, of Bracknell, using new forged pistons from another American firm, JE.

Graham continued the search for even more power, finding a new, even larger, supercharger. It wasn’t a Kenne Bell – a popular replacement for the original Eaton – but an American-made twin-screw Whipple W175AX that, at 2.9 litres, is larger than either the Eaton or the Kenne Bell, yet still fits between the V of the two cylinder banks. “Being different has always been part of the ‘Badcat’ mission,” he says.

Graham asked a local CNC shop, TIAS Engineering, tomachine a single piece of aluminium billet into a connecting plate between the supercharger and the inlet. The spare that he shows me is like everything else about the car – elegantly made (and another indication of his insane level of detail).

Thanks to all these engine mods, the 4.4-litre V8 has reached an astonishing 600fwbhp (around 500bhp at the rear wheels) and 33bhp more than an F-TYPE SVR, transforming this once 20-year-old luxury coupe into a genuine supercar.

It certainly looks the part, too. With its lowered stance – more of that in a second – big front splitter and huge rear wing, the Badcat is similar to Rocketsports Racing’s tubular-framed XKR that won the Trans-Am Championship in 2005. But then, its rear spoiler was influenced by motorsport being similar to one on a GT3 Le Mans car – Graham found the specifications on the internet. “We cut five ribs from solid aluminium billet, inserted threaded bar stringers through the ribs and then wrapped and riveted 1mm aluminium sheet around the form,” he explains. “The end plates were then cut to the same style as the current Emile Frey Racing Jaguar XKR GT3.” The splitter, however, was made to Graham’s own design by the same local fabricator, Gus Robbins, and fits directly onto the nose cone, which was lowered to create a small gap to allow more air under the bonnet.

I might be biased in preferring the car’s sensuous curves in their undiluted form, as in my own X100, but there’s no arguing that the extra adornments make for a very dramatic appearance. There is no doubting these aluminium components are well made and technically more interesting than any bought off-the-shelf, and because the way they have been constructed hasn’t been hidden, the spoiler and splitter look wonderfully aeronautical, as if they’ve been removed from a Spitfire. “I wanted them to appear old fashioned, with visible rivets like the C- and D-type had,” explains Graham, as we walk around his car. The yellow accents contrast perfectly with the car’s original Sapphire Blue and the ring around the front grille is akin to a Fifties sports car.

Graham tells me it was inspired by the 1956 Reims 12 hour winning D-type. “I thought this gave me permission for the accent when challenged by Jaguar purists.” The extra bonnet vents to aid cooling further facilitate its handmade appearance. Again, Graham could have had some off-the- shelf vents welded into place, but, like everything else, he wanted to do it perfectly.

So he bought a second-hand XK8 bonnet and found a classic car customiser that specialised in building rat-rods and who had the machinery needed to press in each of the raise vents individually. Along with the huge air scoop, made by Gus Robbins from a single curved sheet of aluminium, it is a pastiche of a racing car’s, and the properly constructed additions have a professional look.

The interior has received a suitably extreme makeover to match the exterior. A tight Corbeau racing seat, upholstered in the same cream leather, replaces the original, while the fascia is fabricated from a single piece of aluminium in the same curved, Spitfire-wing shape as the veneer. The central console has also been replaced with aluminium, and houses four unlabelled chrome flicker switches. Is one for a second supercharger? Nitrous oxide, maybe? An ejector seat? Knowing Graham, anything is possible. However, the biggest change is to the gear selector and not just because it’s topped by a shiny polished aluminium knob; the J-gate is missing. That’s because the Badcat is fitted with a Tremec T56 six-speed manual, a popular and effective replacement for the XKR 4.0’s original Mercedes-Benz five-speed auto. It has been linked to a competition-spec twin-plate ceramic clutch and servo by American drivetrain specialist McLeod Racing, plus one of Quaife’s famous limited-slip diff’s.

After adjusting and fastening the four-point harness that holds me tighter than an amorous boa constrictor, I twist the key in the ignition and press the starter button that Graham has inserted into the central console. The huge V8 slowly churns into life before it fires, whereupon the ferocity of the bark scatters away birds perched in a nearby tree. I depress the stiff clutch, find first and slowly ease away. Because the XKR’s standard fly-by-wire throttle body has been replaced by a Jenvy 90mm mechanical version, throttle response is progressive – as I squeeze the pedal, power delivery is remarkably controlled for a 600bhp beast. It’s only on a long and empty road that I’m able to safely put the hammer down, upon which all hell breaks loose.

At 3,500rpm and with the huge Whipple supercharger spooled up ready to release its power, acceleration is hard by racing car standards never mind a supercharged Jaguar. Yet, driving this car is like driving something much older, such as a classic Italian V12 supercar. There’s no hesitation in its power delivery, no awkward pause, just an instant and never-ending stream of old-fashioned muscular power. Gone are its Jaguar-like civilities, ousted by a mean and angry character, and its dirty, deafening, animalistic roar is unlike anything I’ve heard from any variety of XKR I’ve driven, including the incredible 5.0 R-S GT.

The clutch maybe stiffer than that on my father’s Leyland 154 tractor, but the six-speed Tremec ’box is fast and accurate while still offering plenty of mechanical feel. Strong and robust, it allows me to slam it hard into gear, aiding rapid acceleration. I change down, slipping easily into third ready to balance the throttle for an upcoming sharp bend. The car’s lowered stance is due to the adjustable dampers produced by British manufacturer Nitron and developed by Tom Lenthall Ltd. Graham tells me that they are not currently at their firmest track setting, yet there’s remarkably little body roll and the car remains calm and composed as I turn the thick, suede-covered Momo steering wheel to throw the big car into a bend.

Before I had set off, Graham had instructed me to switch off the traction control because with so much power the engine could stall if it were to cut in. As a result, I’d initially been hesitant to take a corner too quickly in case it resulted in slide-thunk-bill. Yet, in reality, with so much mechanical grip and effective aero aids, I don’t need it – the car’s fat tyres (255/35/20 at the front, 285/30/20 at the rear) stick to the asphalt and the huge GT3-inspired wing pushes the rear down so that grip is incredible. I can carry far more speed into the corner than I’m used to in a standard X100 XKR. As I come barrelling out of the bend, the car is more composed thanks to the Quaife LSD, ready for me to floor it again, which, like a kid peddling like crazy down a steep hill to generate even more speed, I gleefully do.

The ride is granite hard, though, and I can detect even the smallest piece of gravel beneath the tyres – meaning that on this typically British uneven country road I’m being shaken harder than a salad dressing. Yet I’m enthralled by the Badcat, and not just because of its speed, but also because of the engineering behind it. With every aspect of the car having either been changed or uprated, it reminds me of the track-ready Palmer Sport XKR I tested; both that X150 XKR and this X100 are pushed to their limits. But whereas a team of specialist motorsport engineers developed the PalmerSport XKRs with a little help from Jaguar, Graham has modified his car with nothing more than some good ideas, a little ingenuity and plenty of patience to get it right. And, perhaps just as importantly, a big chequebook.

Thanks to: Graham Wood (



TOP LEFT: The GT3-inspired spoiler with Emil Frey-style end plates. TOP RIGHT: Huge air scoop is made from one single sheet of curved aluminium. LEFT: leather-trimmed Corbeau racing seat with four-point harness. ABOVE: Manual gear lever for the Tremec six-speed transmission. ABOVE: Single piece of aluminum now houses the dials. ABOVE: Arden rear light clusters.


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