It's not that they're an afterthought or a profitable side line; rather, they're a spasmodic and unpreventable release of the latent enthusiasm that builds up when you are forced, for very good reasons, to spend most of the year grinding out Avensises and Aurises.
The discontinued Lexus LFA, a money-losing masterpiece that could not perhaps have been built anywhere else, is the most obvious example of this cathartic approach (although the current Toyota GT86, an extraordinary attempt to hotwire a niche concern into a mainstream offering, must run it close).
The IS F, though, predates them both. The four-door saloon, introduced in 2007, was more obvious territory for Lexus, but it was still conceived and developed in a way that made it seem more like muscle spasm than cast-iron range inclusion. It drove that way, too, being amusing and wayward and worrying in divertingly unequal measure.
The newer, fewer-doored Lexus RC F, our reason for assembling the cars that you see above, is an indirect descendant of that car - chiefly through its 5.0-litre V8 petrol engine.
In Europe, the repeat appearance of so many atmosphere-munching cylinders has provoked a collective raising of the eyebrows, most of them questioning the need for quite so much cubic capacity when the opposition - namely BMW and Mercedes-Benz - are now extracting more from significantly less.
Such dubiousness is valid, of course, if a little Eurocentric. Lexus is using the V8 not because it's a warbling throwback, but because it's the Euro 6-compliant global engine available, it being a tricked-up version of the unit that is slid into more humble fare, often with electric motors attached. This is why it can be made to function on the fuel-sipping (and gently power-sapping) Atkinson cycle, should you wish to attempt to draw the quoted 26.2mpg out of its hat.
Since the IS F, it has been revised again, mostly to make it rev higher and harder, producing yet more power along the way. The resultis the most powerful road-going Lexus V8 yet - the marketing department's way of saying that it's 54bhp perkier than before.
That, at least, compares favourably with the competition, a Germanic collective that is bisected by the RC F in terms of engine technology. On one hand, there's the new BMW M4, torch-carrier for a future generation of cars dependent on forced induction.
On the other, there's the Audi RS5, a leftover from the soon-to-be-extinct era when it was deemed okay to mount a supercar's engine over the front axle and holler out “finished” to the rest of the factory. The M4 develops 425bhp and the RS5 444bhp, leaving the RC F, at 471bhp, looking even more muscle-bound than its many bulges already suggest.
Each, though, will do 0-62mph in about 4.5sec, seat four people in relative comfort and set you back the best part of ?60k. Their designers shared a style guide, too, each being a different version of the same raked, narrow-eyed, cold-shouldered brute. The eldest, the RS5, has a certain Q-car subtlety about it.
The newest is a Japanese Brillo pad of ideas, some half finished, others overplayed, still more just stuck on for fun. Visually, it rears up at you like a manga trailer. Most likely, it suits neon and steam, not the investigative white light of the Peak District.
Inside, it swerves so violently back to the straight and narrow that you'd think the right hand missed a memo from the left. Lexus, apparently oblivious to Jonathan Ives' plasmatic revolution, builds interiors as though it were working to a 1970s Xerox R&D blueprint.
There must be 30 buttons on the RC F's centre console to go with a brusquely gated gear selector and, yes, a touch-sensitive mouse pad. Everything slots together as though it has all been machined from a single three-metre-square cube of high-grade plastic, and everything is done better - prettier, suaver, sleeker - in both of its European rivals.
Switched on, warmed over and driven in the default condition of many, many modes, each car telegraphs a different take on what expensively rendered normality should feel like.
The RS5, defined by its supreme Audiness even late on in its lifecycle, still girdles you in an unyielding pressure chamber of refinement. On passive dampers, it rides with a thick-necked stubbornness and steers with brooding intent. It feels nose-heavy and tacked to the planet like a continental shelf. It would be a boorish nuisance if there wasn't so much effervescence shimmering off the 4.2-litre V8's 1-5-4-8-6-3-7-2 firing sequence.
This, surely, was the engine on Lexus's benchmarking spreadsheet - the reason for its new titanium valves and forged conrods and that higher 7300rpm limit. The Audi unit, peppered with the nonchalant blips and clicks of its quick-witted seven-speed dual-clutch automatic gearbox, goes farther around the rev counter by almost 1000rpm, every last speck of it in a distant fuel-stratifying trill of moving parts. It is that rare and special sort of motor which has you pondering the remarkable stresses it must be under without ever considering its preservation.
In the M4, on the same damp hillside, your thoughts are more likely to turn to the welfare of your own internals. The rear axle is rebellious to the point of outright silliness in poor weather. Blithe throttle inputs of the size swallowed by the quattro drivetrain will have the back end trying to overtake the front, a tendency even repeated between the pugnacious, head-nodding manual shifts of BMW's more aggressive seven-speed M DCT.
Such overt waywardness can only be intentional - part of M division's grand scheme to ensure that its most famous son cannot be accused of detachment or dullness. Better that it growl and spit like a risk-inclined mongrel occasionally if that's what it takes to stage manage the right kind of instinctive directional energy.
This it manufactures in prodigious quantities, partly via a typically direct steering rack and its lighter, better balanced kerb weight, and partly through the viciousness located beyond the bulkhead.
There's no aerated V8 fizz here, but rather a spooled-up industrial retort from what can only be described as a glowering petrol generator of a 3.0-litre straight six. Its turbos are twofold, dinky and intended not to hinder an engine that revs, via its own set of exotic components, to well beyond 7000rpm. That's despite forced induction. The benefits of it are felt much sooner, most obviously in the savage 406lb ft of torque that it belches onto the road from 1850rpm.
It is this rip tide of coercion - summoned from less than half the crank speed of its rivals - along with the 30mpg-plus the M4 returns on the motorway that threatens to sweep the atmospheric V8 into superfluousness.
The RC F certainly has no answer. Driven modestly, it is treacly by comparison, defaulting to a baritone and gentlemanly obedience below 4000rpm. There's a hint of waft, even, helped along by the nebulous upshifts from the only conventional automatic present and a throttle that's apparently indifferent to the first few inches of pedal travel.
It can't quite match this coyness in the suspension, where the rebound is a little too eager to keep the car on an even keel, despite the bony repercussions. But it is a considerate package, nevertheless - less alert, more hospitable. Imperiously Lexus, then.
To cast off the stateliness, one must either cycle through the four drive modes or else bring your size nine down to meet the nylon shag. Either way, somewhere in the mid-range, the exhaust, or the speaker beneath the instrument cluster frantically channelling the exhaust, finds its voice - and the new valves, injection system and cylinder head finally show their worth.
The needle's sprint up to the redline isn't as riotously quick as in the RS5, nor the thrust that accompanies it on par with the M4's, but the V8's climactic roar is almost as compelling because of the sense of heft that comes with it - like feeling the ground shake beneath a charging rhino. Transferred to the wider asphalt of Blyton Park circuit, the RC F is the one car here that feels as though it could use the space of the long back straight to expend its full, long-legged potential.
In some measure, that is the shortcoming of the eight-speed auto 'box, which really must be shifted manually if you don't want to wait for the old-fashioned delay of an elastic-band kickdown. But mostly, it's the fault of the coup?'s kerb weight, a 1765kg millstone (minus driver) that somehow manages to make the extra mechanicals of Audi's all-wheel-drive car appear undernourished. The RC F carries this extra mass around a track conspicuously, making it more numb and less wieldy than it deserves to be.
The nervous system beneath the fatty tissue is clearly functional, though. Squat and appreciably more adherent than the M4, the car makes the most of its firm chassis and can be cornered with the kind of confidence that comes from knowing the front will start hinting at you before the back gives up. Optionally, there's a torque-vectoring differential to help smooth the transition from neutrality to tyre-spinning excess, a state that it handles with manageable panache.
The verdict
The RC F's adjustability and briskly fluent steering almost has it pip the RS5 in the final running order, especially given the inordinately massive lift-off required to have the Audi reconcile itself with a new line. But the RC F's ultimate inability to satisfy at either end of its changeable nature - not as a big-chested GT or flat-out thrill seeker - dooms it to Toyota's catalogue of nice ideas rather than its shortlist of unmitigated triumphs.
The RS5, certainly at Blyton, isn't any more lovable. It is, as you would expect, plainer, stickier and faithful to the point of brute force. It won't have you yearning for another lap or desperate to find the keys in your pocket when it's all over, either. And yet, unlike the Lexus, it has one virtuoso aspect in that princely V8. It also has the means to deploy it, one not dependent on the weather, time of day or even a basic level of attention.
Although, if you get the chance, we'd advise you to sit up straight; there's a man in Ingolstadt right now plotting this engine's demise - and when it's gone, there won't be another like it.
There will be more like the M4, though, and that's fine. Its laps rumble through the memory in a sweaty blur. But then there were a lot of them. The car is, at once, tenacious, tiring and ballistic. Even in drier conditions, the limits of its traction are not typically progressive.
The uptight diff makes the rear end a twangy affair, and although the chassis telegraphs it plainly enough, it doesn't make for an easy-going experience. It is an invigorating one, though, and that's largely the point.
Much about the BMW - its steroidal engine, vociferous soundtrack, delinquent handling bias and so on - is an instant fix, each made so immoderate that you could access them on your driveway. Flagrant hedonism doesn't make it perfect all the way around, but, boy, is it a coupe for our times.
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