1998 JAGUAR XKR "Badcat" Manual

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1998 JAGUAR XKR "Badcat" Manual


Launched in 1996 and always more of a grand tourer than an out-and-out sports car, the Jaguar XK8 shared its chassis with the Aston Martin DB7, making it the thinking man’s choice for anyone in the market for a powerful, rear-wheel-drive luxury sports car.

Available as both a 2+2 coupe and a convertible, the XK is, like the Kray twins, available in two varieties: mad and madder. The mad one, which we’ll call Reggie, is the XK8. Fitted with a normally aspirated V8 engine - albeit one with four litres and 32 valves - it develops 290bhp and 290lb/ft of torque, enough to propel the XK8 to a top speed of 155mph after passing 60mph in under seven seconds.

Ronnie, Reggie’s even madder twin brother, is the XKR. Ronnie has a supercharged V8 under the bonnet - and that Eaton supercharger spins at almost twice the engine's speed, helping it churn out 370bhp and 387lb/ft of torque. So while the XKR shares the same artificially limited top speed of 155mph as the XK8, it knocks around a second-and-a-half off the normally aspirated car’s 0-60mph time, clocking in at around 5.5 seconds.

Whilst those figures might be impressive for the XKR; it wasn't quite enough for our petrolhead vendor Graham, who in 2007 embarked on a 13-year journey to improve and modify the once standard 1998 XKR into this stunning 632hp unique Jaguar, more commonly known as the ‘Badcat’

The Vehicle

There's no denying this car is undoubtedly unique and probably one of the most developed XKR’s in existence. We will start with how the Badcat developed over the 13 years to produce the impressive 632hp and an astonishing 805 nm of torque.

The Badcat started life as a 1998 Jaguar XKR, which Graham saw for sale in 2007 and having a soft spot for the X100, plus having been looking for a car for a while, this was snapped up straight away. Driving the car for a few weeks was enjoyable, but as with any petrolhead, it wasn’t long before Graham started looking into tuning options for the XKR.

This started with a smaller top pulley and larger bottom pulley fitted to the supercharger, and this was complemented with a Racing Green ECU piggy back upgrade to keep on top of the fueling due to the faster spinning supercharger. The result was 456hp, an impressive 64bhp gain from the standard bhp.

With the 4.0 litre pushed to its limits, Graham was on the lookout to further improve the performance of the XKR, and this was the start of taking the car to an entirely new level. Graham found a new Range Rover 4.4 litre V8 which became the next base for the project. The engine was rebuilt using stronger high spec’ bespoke forged pistons from German automotive parts manufacturer Capricorn, which kicked off the need to have parts purpose made rather than buying off the shelf items.

The upgrade to the 4.4 litre brought the power up to an impressive 480bhp; it was never quite enough, and the need for more power continued. This need was realised when in 2012 when Graham, assisted by Jaguar expert Tom Lenthall, found an uprated Eaton supercharger which was originally destined for an XKR GT3 racing car. This was fitted along with some other improvements to bring the XKR to 510hp.

In 2016 whilst on a track day at Goodwood, flying at over 140 mph, the 4.4 litre detonated, melting five out of the eight pistons. The cause was put down to poor fuel pick-up from the standard Jaguar tank, which would later be resolved with a bespoke designed, foam-filled ally fuel tank with swirlpot fabricated by CKL Racing, containing two Walbro 450 high-pressure fuel pumps. Only one of the pumps is needed and more than capable of providing enough fuel for spirited driving; the other pump was simply fitted as a backup. Luckily the cylinder block suffered only minor scoring and was sent off to be rebuilt at performance engine experts Classic and new forged pistons from JE in America. This gave Graham the opportunity to develop even more power, and with a freshly built engine, a new twin-screw supercharger, a Whipple W175AX, was sourced from the USA. Although being told it would not fit by the company director, Graham had other ideas. With some well calculated CAD drawing and CNC machining, the charger was made to fit, pushing the XKR to the enormous power it now produces.

This is just a very, very small part of the 13-year ‘Badcat’ development, explaining how the car ended up with the power it now runs. The whole research and development program to achieve this build is fully documented and shows the prototype costs and parts trialled and fitted to achieve this unique concept, which cost comes in at more than £178,000 and that doesn’t even include the initial cost of the car or any of the owners time..

On the Outside

Badcat by name, Badcat by nature and Badcat by looks! This 1998 Jaguar XKR has had everything it needed done to the aerodynamics to to match the power. After running the car even with an enhanced 510hp, possible cooling issues were addressed. As much cold air as possible would be needed into and out of the engine bay, when the final power upgrades were completed. . It was soon realised that as much cold air into the engine bay as possible would be needed when the car was completed with its new engine and supercharger. This has been achieved by using the bonnet from an XK8 and then adding 52 hand-pressed louvres and having an air gap at the front (which to some may look like a poorly fitting bonnet); we can assure you this is intentional. Air is additionally drawn in through the gap between the nose cone and bonnet; as it moves over the engine, it collects hot air and vents via the 52 louvres, lowering the engine bay's temperature. The large open-mouth bumper and air scoop on the splitter directs more air to the intercooler, ensuring the charge cooling system works as it should. The bespoke ally splitter adds downforce, giving the front wheels that extra grip. The headlights have been upgraded to HID, offering a welcomed improvement over the originals.

Looking down the flanks of the Badcat, there are no dings or dents to mention, and the doors align as they should. There are a few age-related stone chips here and there, as you would expect because the car had been designed to be used, which is just what Graham has done. The windows look to be in good condition, as do the aluminium trim surrounds. There is a small amount of corrosion creeping in on these, but nothing a quick rub down and repaint wouldn't sort out.

The rear end has also been catered towards the amount of power the XKR is pushing, with the fitment of an adjustable spoiler adding more downforce to the rear wheels also balancing the front splitter. The light clusters are made by Arden and have the twin light design, and these are in excellent condition with no splits or cracks.

To keep you connected to the tarmac are a set of 20” deep dish Ascari Penta wheels which have had the centres powder coated to match the exterior colour. These are fitted with a matching set of Michelin Pilot Sport R wall tyres which have a good amount of tread remaining. Graham also includes a set of 18” Hydra track day wheels complete with spacers. There is a set of Toyo 888 tyres fitted, and these have been scrubbed in, ready for use.

On the Inside

Inside, the Badcat has something for everyone. Whilst, on the one hand, it resembles a race car pedigree, on the other hand, most of the creature comforts have been retained, thus offering a level of normality. The driver's seat has been replaced in favour of an FIA approved Corbeau Sprint race seat trimmed to match the rest of the interior. The passenger seat is the original, which has retained the electric functions but has been stripped down and reinforced to accept the 4-point Luke racing harnesses fitted to both front seats. What is nice is that the original inertia factory seatbelts have been retained should you fancy a trip out in the XKR without being in full race mode (it probably won’t happen, but the option is there). There is also an intercom system which includes two sets of headphones with amplified volume controls and a universal feed for the addition of in-helmet speakers. The rear seats are in good condition but do have the harness attached between the base and backrest, but to be honest, in an XKR, it isn’t the most practical of seats, so there is no significant loss.

Sitting behind the MOMO D Alcantara steering wheel, there is some wear to the rim, as you would expect to see from Alcantara. The dashboard has been finished in a hand built one piece aluminium facia and the instruments directly in front of you are the originals. Up to the right in eye line view is a Race Tech tachometer and to the left is a GPS speedometer. The dials to the centre are the new tank compatible fuel guage and oil level, with the addition of an AEM Realgauge, which provides oil pressure, coolant and air temperature, Lambda values, supercharger PSI and oil pressure. The centre console retains the original head unit and the Harman Kardon premium sound system, which has a boot-mounted CD multichanger. The heating controls, including the air conditioning, are working as they should and just behind the billet aluminium gear knob is some additional toggle switches fitted to control various functions.

The carpets are generally in good order with just some wear to the driver's mat, which is in keeping with the age of the vehicle; under this, the original carpet shows little signs of any wear. Inside the boot, there is some space remaining, but some has been commandeered for the fitment of the foam-filled fuel tank, as mentioned earlier.


As we briefly explained earlier, the Jaguar is now running a rebuilt 4.4 litre V8 which has been hand built by C&M Engineering using bespoke parts. Since the rebuild in 2018, the engine has covered just 20,000 miles.

The rebuild started with bespoke forged pistons, which were fabricated by JE Pistons in the States. The cylinder heads have been ported and matched to the inlet manifolds where there is the creme de la creme of superchargers, fed via the plenum airbox and the huge bonnet air scoop; the Whipple 175 AX 2.9 litre charger is fed by a Jenvey 90mm progressive throttle body . Opposite the inlet are the exhaust manifolds, which have bespoke Badcat 4-2-1 tubular stainless headers , which have been Zircotec heat coated and coupled to a de-cat stainless steel exhaust system with a centre box and twin back boxes per side. Graham also includes with the sale of the car, two new matching downpipes and integral 200-cell cats. The ECU is a stand alone AEM S2, which has been mapped by SRD tuning. Managing both engine temperature and importantly air intake temperatures are the charge coolers fed through an RX Superchiller, a refrigerated AIT system, an additional heat exchanger, a large intercooler, and a high-flow coolant pump with an auxiliary second fan. Finally, to keep the oil stable, there is a high spec oil cooler and uprated pump.

With all this power and to enhance the driving experience, a manual transmission (a rare conversion) is demanded. A transmission capable of coping with everything it may endure on a spirited drive. This has been achieved using a Tremec 6-speed manual gearbox with a McCleod twin plate ceramic clutch. There has been a Quaife limited slip differential fitted, and the prop shaft has been reinforced and balanced.

On the handling and stopping side of things, as well as the lowered stance, Graham has opted for Nitron coilovers which have 24-position adjustable damping to ensure the perfect set-up. Bringing the Badcat to a halt are larger vented front discs with Brembo calipers and EBC Yellow Stuff pads. Even with all the modifications the XKR has, they have been carried out in such a way that the car is still very usable and driveable around town, and you don’t need to be going flat out everywhere to enjoy it.

History Highlights

This whole build has been developed over 13 years at a cost of over £178,000, which is fully documented down to the last nut and bolt. Along its journey, Graham has dealt with some of the best people in the business, from engine builders, CNC machinists, car designers/ builders and senior Jaguar technicians. Even receiving commendation from Ceasar Pieri, who, as the Jaguar Advanced Design Manager, said how impressive the Badcat is.

The Badcat is a well known car in the Jaguar and motorsport world and certainly no stranger to being the centre of attention either on the front cover of several magazines such as Jaguar World, Growler magazine, and Jaguar Driver Performance, to name a few and then also going on special display at some high-level events around the country. You can even visit the Badcat website, where amongst a whole host of information on the car, particularly the Dyno power graph, you can also see the car in action at the Goodwood Motor Circuit http://www.badcatjagupgrades.co.uk/

What We Think

What more is there to say about this amazingly unique and bespoke build, with over 13 years and over £178,000 spent on research and development. Everything has been logged and itemised, which will give you the entire tale as to just how much work has gone into creating something truly original.

It is a really exciting opportunity for someone to own the Badcat and probably the most developed XKR X100 in the world. Especially now, as it has a new 12 month MOT expiring at the end of May 2023!

We estimate this one-off Badcat to fetch in the region of £25,000 - £50,000

Viewing is always encouraged, and this particular car is located with us at The Market HQ near Abingdon; we are open weekdays 9am-5pm, to arrange an appointment please use the Contact Seller button at the top of the listing. Feel free to ask any questions or make observations in the comments section below, or try our ‘Frequently Asked Questions.’

If needed, Footman James classic car insurance and Classic Concierge offer storage options plus we have a list of contacts who can help with transport and shipping.  

BORING, but IMPORTANT: Please note that whilst we at The Market always aim to offer the most descriptive and transparent auction listings available, we cannot claim they are perfect analyses of any of the vehicles for sale. We offer far greater opportunity for bidders to view, or arrange inspections for each vehicle thoroughly prior to bidding than traditional auctions, and we never stop encouraging bidders to take advantage of this. We do take a good look at those vehicles which are delivered to our premises for sale, but this only results in our unbiased personal observations, not those of a qualified inspector or other professional, or the result of a long test drive.

Also, localised paint repairs are common with collectable and classic cars and if they have been professionally carried out then they may be impossible to detect, even if we see the car in person. So, unless we state otherwise, please assume that any vehicle could have had remedial bodywork at some point in its life.

Additionally, please note that most of the videos on our site have been recorded using simple cameras which often result in 'average' sound quality; in particular, engines and exhausts notes can sound a little different to how they are in reality.

Please note that this is sold as seen and that, as is normal for used goods bought at auction, return policy does not apply. See our FAQs for more info, and feel free to inspect any vehicle as much as you wish.

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Graham Wood

  • Location: The Market HQ, Abingdon, United Kingdom
  • Seller Type: Private
  • Odometer Reading: 168333
  • Chassis Number: SAJJGAEF3AR028666
  • Engine: 4400cc
  • Gearbox: manual
  • Steering position: RHD
  • Colour: Sapphire Blue Yellow Accents
  • Interior: Ivory Leather
  • Estimated Price: £25,000 - £50,000

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