How Do You Make A Chassis Go From This ….To This?
01 May 10, CAR, Ben Barry
Ask any of the team behind the XFR about what shaped this car's gestation and you'll hear one word again
and again: duality-the balancing of everyday refinement, luxury and usability with a raucous streak. They'll
also talk about trying to get the personality of the team to shine through in their product. It does, but Mike
Cross - a real-life Jekyll and Hyde - best sums up that ethos.
Meet Jaguar's chassis guru and you'll be struck by how understated his gestures are, how measured he is
in conversation. You might picture him spending Saturday night with a cuppa, a pair of slippers and the
paper. Yet here's a man who'll throw a Jaguar up the narrow Goodwood hill climb, pitching it sideways
before corner entry and exiting with a trail of tyre smoke and a stunned silence from the crowd. The man can
drive. now I've got two days with him at an empty Anglesey circuit, plus a van full of tyres and a pair of XFRs
that are raring to go. Faintly intimidating, hugely exciting.
Two days earlier and the security barrier at Whitley lifts to grant us access to Jaguar's engineering HQ.
There are XJ mules, the first XFR prototype, other cars with mismatched black and red wheels. 'red means
the wheels are the correct weight and strength, so they're essential for chassis development,' explains an
engineer. 'That's probably a powertrain development car, so it's not so important if all the wheels aren't quite
right.'
Around 200 people worked on the XFR, but closer to 10 really shaped it, and today we've got six of them
together, Cross being otherwise engaged with Jaguar Land Rover owner Ratan Tata.
The vibe is laddish pub banter. There's Big graham, Baby-Faced Matt, talk of a fledgling band that they
should really get out gigging, puns that can't be printed in a family magazine and jibes for vehicle refinement
engineer Stuart Adlard. 'remember the sign-off run for the XFR in Germany?' chortles vehicle engineering
manager Graham Williams. 'he thought he'd got through the worst on the autobahn...' 'Yeah, rang me wife,
said I'd done the worst bit,' nods Adlard, staring at the floor. 'Pffft. Then we took him on the back roads,' says
Big graham. 'his face! remember!? Pffft. Your face, mate!'
In fact, such is the incessant, blue-collar Mickey-taking it's easy to forget that every one of the blokes here is
hugely skilled, has massively, obsessively specialised knowledge and can talk eloquently about the minutiae
of engineering components that some drivers wouldn't miss if they were removed altogether.
'we started working on the XFR just as we were making the first XF prototypes,' says vehicle integrity
engineer Jeff Mitchell. 'we could only guess at how the press and public would react to that car, so in some
ways it was a shot in the dark to be already making the hot version. But we set out to build a car that was
more tactile than the Merc CLS AMG, not as daunting as an M5, and I was confident that we were moving in
the right direction.'
It started in 2007 with an XF mule equipped with the 5.0-litre supercharged V8 and electronic differential,
the latter shared with Land Rover but massively retuned for performance work. 'They're blunt instruments at
first,' says chief programme engineer Kevin Stride. 'we do tuning batches, so different prototypes focus on
different aspects - chassis, powertrain, refinement and so on.'
By November 2007 the team had a representative prototype - the same mule that Cross would later scorch
up the Goodwood hill come summer 2008-and came together to finesse the disparate elements into one
harmonious whole. 'we had what we call a basic hygiene level,' explains Stride. 'The maths give you a level of
competence, but you don't really know how it feels. we wanted to shift that competence to excellence, and to
do that we had to trust one another and go more by feel.'
Jaguar News
23 Apr. 10
Produced by Jaguar Land Rover Public Affairs 6
The steering rack became 15% quicker for greater agility; the standard car's fixed-rate dampers were
replaced with continuously variable Bilsteins; the engine swelled from the 4.2-litre supercharged V8 seen in
previous hot XKs to a healthier 5.0-litre; the electronic diff was tuned to tame the 503bhp and 461lb ft going
to the rear wheels; 35 different rear exhaust boxes were tried before the team hit on just the right kind of
cultured note.
The press launch came in early 2009. Car placed the XFR above Audi's RS6 and BMW's M5; other positive
reviews followed. 'They couldn't have been much better,' smiles Kevin Stride. 'But I think the high point was
beating the M5 in a one-marque German title. Bet their readers loved that!'
1 SUSPENSION
The XFR doesn't have in-car adjustable dampers, but its hydraulic Bilstein units are continuously variable,
meaning they are supple at low speed but firm up in direct relation to building cornering forces thanks to a
solenoid-operated bypass valve that alters the hydraulic pressure. Endless variations were tested and
discarded. The XF Diesel S's less-than-perfect ride will soon be improved by adopting the XFR's tech.
2 DIFF...
With 503bhp and 461lb ft, the engineers knew they couldn't stick with the open differentials previously used.
Unlike other manufacturers' traction control-based electronic differentials, Jaguar's E-diff is a proper
mechanical unit, but it's electronically controlled. 'A normal locking differential is passive and has to react to
slip,' explains engineer Tim Clark. 'So it has to be very tight to be effective which isn't so good for everyday
refinement. The E-diff is active, so it calculates steering angle, torque, wheel slip and yaw and responds
instantaneously. It can also lock by 100% on acceleration and deceleration where most locking diffs are 20-
30%. But it's more like an open diff in normal driving, and so more refined.'
3...AND GEARBOX
The E-differential hooks up with a conventional-sounding six-speed torque converter gearbox (yes, okay, it's
at the front of the car and you can't actually see it here), but one that hides a few tricks up its sleeve. For
instance, the converter slurs for silky smooth parking manoeuvres, but locks from second gear onwards for
direct gearshifts. The software is also in-car tweakable. Stay in Drive and the auto mode will always prevail,
even if you occasionally intervene on the paddles. Select Sport and the shift mode becomes more
aggressive and won t revert to auto once you've selected a gear via the paddle-shifters. Sport also adapts to
your driving style, but it will still change up at the limiter. Press Dynamic and you can hit the limiter, the
suspension and steering subtlety firm up and the gearbox limits the extent to which it adapts - it will always
retain a slightly manic edge, no matter how docile your driving. In all modes the kick-down step is still active.
Elsewhere, winter mode brings a 10-15% less aggressive throttle, plus more lenient traction control (some
wheel slip is beneficial in snow...) and earlier stability control intervention (...while getting out of shape isn't).
4 EXHAUST
Unlike Aston Martins, which use active bypass valves to make their exhausts suddenly louder above a
certain rpm threshold, the XFR uses a progressive valve so the soundtrack swells from barely noticeable at
cruising speeds to an insistent, throaty gurgle under heavier throttle loads. Asymmetric exhausts bring more
of an offbeat burble, and, during development, hatches cut in the silencers gave the engineers easy access
to experiment with baffles and fine-tune the soundtrack.
Now it's time to reacquaint myself with the XFR on the excellent welsh roads that all Jaguars are honed on,
before hooking up with Mike Cross and heading to the sweeping corners, dramatic elevation changes and
epic cliff top views of Anglesey race circuit.
There's nothing like an exciting car to overcome a horrifically early start and I positively bound out of the
house at 5.30am, plip the keyfob and sink into the XFR's plush leather chairs, press the starter button and
listen as the engine settles with a breathy, offbeat woofle that sounds ocean liner unstressed. There's a
loungey ambience inhere that reminds of gentlemen's clubs, understated evening wear and business class
travel- even the bottoms of the cupholders look like they've been turned from hunks of solid metal.
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23 Apr. 10
Produced by Jaguar Land Rover Public Affairs 7
The world feels like a safer, warmer place and, for the first time ever, I select radio 3 on the DAB radio, ramp
up the volume and let those sweepingly epic classical numbers seep through the Bowers and Wilkins stereo
system. Then catch myself- I'm not that old yet -and realise I really should make the most of Dev on radio 1
before that oaf Chris Moyles comes on at 6.30am.
I absolutely 100% convince myself that it's a long four-hour run and it's probably best not to turn the traction
control system off, but the maladjusted side of my brain takes over and I find myself reaching down and holding the
button for 10 seconds to ensure all safety nets are removed. Ten seconds is too long when you spy a slideable bend,
so you might as well be ready for sergeant sideways duty.
Cambridgeshire A-roads and dual carriageways are effortlessly dispatched in darkness before daylight
dawns with a soporific grey blue pallor and we're onto the M6, skirting around Birmingham, spearing west
towards wales on the M54.
The steering feels incredibly light and quick to react without being nervous, and it still telegraphs enough
road surface data to keep you informed; the throttle response is quite edgy, at first slightly clumsy, but you
learn to modulate it more gently, tipping it in, easing it out; the chassis flows with the undulations of the road
and subdues most secondary imperfections, but isn't so cosseting as to entirely quell the fizz of a chassis
interacting with tarmac; and the gearbox - a disappointing sounding six-speeder- actually works superbly,
offering all the silky manners of a torque converterwith quick changes and a well-reasoned auto logic.
By the time the A5 gets interesting I've been driving for well over two hours and couldn't have felt much
fresher in a Mercedes S-class. Then the fun begins as I dive down a B-road and start to work the XFR more
aggressively. The V8 takes on a harder edge, I switch to selecting gears on the paddles and the car instantly
morphs from exec cruiser to B-road slayer. The acceleration always feels absolutely instant, hugely muscular
and entirely linear - the stats tell you that all 461lb ft is with you from 2500rpm to 5500rpm but you're never
really aware of it coming on stream or tapering off- the gear changes are robustly instant thanks to a torque
converter that locks from second gear onwards to abolish that frustrating slush, and the steering ups its
game, giving you weight to work against as you commit more fiercely to bends.
And, you know what, despite the massive power and torque reserves, the traction is actually very good
indeed. I try to get the rear end working and at first I'm too tentative, too mindful of the XFR's rep as a tyredetonating
mobile, so I start by going deep into slow corners before timidly flattening the accelerator and
emerging with something of a tank slapper. with acclimatisation I learn it's all about having the confidence in
the chassis to go in early, so I accelerate gently but insistently just as I'm turning into a second gear turn,
the back progressively relinquishes grip and I slide through the bend while having a quick enough steering
rack to keep my hands in the same position, then pull for third and, ahem, overtake the poor bloke I'm tailing
whose eyes are by now actually bigger than his rear-view mirror.
after half an hour I've totally bonded with the XFR and even eke a delightful smudge of oversteer through a
fast, well-sighted corner in third and involuntarily yelp in delight. I know, I know, it sounds mad and
irresponsible, but these roads are deserted and the limits are lower on this car and easier to read than in,
say, an M5, so if you've got even a mill of superplus in your veins you'll get curious, you'll get braver and
eventually you'll learn to exploit the XFR and trust its benign balance.
If anything the XFR doesn't work quite as well as 2008's superb XKrS on these roads, but it's only when you
start pushing to the extremes that you notice. You can't quite work the front end as hard, don't feel quite as
confident leaning all the weight of the nose on the sidewalls of those 20in tyres, can't quite take as many
liberties with your inputs as you could in the nimbler XK. no, the better bet is to ease back a little, plan
further ahead and attack the bends in a more thoughtful, more joined-up manner. Do that and you'll have a
blast, and, really, to ask for more is a little greedy. I'd honestly take the small dynamic penalty for the extra
all-round ability. That said, the engineers nudge and wink and hint about getting ready for the upcoming M5,
quiz me on what I'd want out of, oooh, let's say an XFRS, and mention that the same-sized wheels with
wider front tyres might add the extra bite I crave. Seriously chaps, only do it if the car's equally comfortable at
a cruise.
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23 Apr. 10
Produced by Jaguar Land Rover Public Affairs 8
We rendezvous with Mike Cross and roll into Anglesey race circuit in convoy just as thick black clouds roll in
from the Irish Sea, pelting the circuit with heavy slugs of cold, hard rain. The grass at the edge of the circuit
glows a lustrous green and quickly saturates, and the track surface runs a glossy black with streaming
water. Yikes. Cross tells me that the new E-diff- a good old-fashioned English name as pub landlord al
Murray might comment - is great because it gives you traction when exiting junctions and is safer during
emergency lane changes. But it's also very good when you knock all the traction aids off and go absolutely
mental, isn't it Mike? 'Yes, that too,' he smirks. 'That too.' On cue we're into a fast corner, Cross confidently
and smoothly kicking the tail out while keeping hold of the wheel with one hand, a benefit of the faster
steering rack. It's different to my own technique of letting the steering wheel slip through my fingers as the
car swings to its maximum angle, before holding it firmly and feeding it with both hands to control it on exit
as the attitude reduces and the threat of a snap back in the other direction looms large. each to his own, and
the one-handed approach obviously works soundly enough for Cross. I reckon his sideways face is far
superior to mine, though.
Cross is incredibly proud of the XFR. 'It's the first time we've had all the componentry - the more powerful
engine, the E-diff, the stronger structure, the transmission- to go head-to-head with the Germans,' he
reveals. 'But when we started work on the car I was worried that the engine could dominate the package. It
doesn't, and I'm really pleased with the way all the components work together in harmony.'
After a couple of very fast sideways passenger laps I head out in my XFR, select Dynamic ('it'll let you hit the
limiter with that selected,' says Cross), hold down the traction control button for the regulation 10 seconds
and twist the rotary gear controller to Sport so that the auto mode won't intervene when I use the paddles.
at first we lap separately, exploring each and every corner in relative safety, all of which, as luck would have
it, are on for a bit of tomfoolery, even if some are dauntingly fast and initially invite a cautious approach that,
ironically, makes failure even more likely. with the surface so wet and the XFR so soft - the very reason it
works so well on the roads we've just driven - there's some frustrating understeer to manage at first,
especially on the slower corners, though the faster ones bring speed, and with that comes the potential for
weight transfer - the ultimate understeer bypass.
The soft chassis also brings weight transfer at the slide's end, meaning a progressive lift off the throttle and a
controlled drift back in the opposite direction is the best option for a smooth exit, odd as it at first feels to be
swinging away from the corner and back. The diff feels fantastic, always like it wants to hold a secure, fairly
straight slide that you work to tweak. It responds instantaneously too.
Before long our sliding cars are tucking up next to each other, Cross leading as I dive in alongside him, me
always wondering if his heroic amounts of steering lock will turn into a spin, him remaining resolutely focused
on his exit strategy. Soon enough we learn to trust each other, and the entry speeds become ever dafter and
dafter with judicious egging on from our camera and video crew - you can see the video on
carmagazine.co.uk-and some local builders. 'Faster!' 'Closer!' 'Crash!' It's laugh-out-loud ridiculous.
But let's not be immodest here - it isn't two days packed full of perfectly controlled powerslides and
beautifully balletic transitions. Sometimes I run out of lock and Cross has to take evasive action; other times
he spins in front of me and I have to quickly stand on the stoppers. 'They say to aim for the spinning car,'
Cross will say later, and we'll both stand there mulling it over and umming before deciding that, no, 'they've'
actually come up with a spectacularly bad idea. when we finally stop we're laughing at the sheer lunacy of it
all, relieved that both XFRs have emerged unscathed, but mentally and physically exhausted - my left knee
is heavily bruised from constantly bracing it against the transmission tunnel during big slides, my legs feel
lead weight heavy and my right foot twinges with biting cramp. Seriously, it's proper hard work, this. not that
I'm expecting any sympathy. Yet barely 10 minutes after the track has closed for the night, Mike Cross is
back to his newspaper-and-slippers best, talking about what a mess his two daughters make when they
come home from university and how he likes to relax by tinkering with his beloved motorbike when it all
becomes too much. Intelligent, reserved but with a wicked sense of fun, Mike Cross and the XFR are perfect
metaphors for each other. They just couldn't be more similar.