That’s the speed at which a British Touring Car Championship-spec BMW 3-series is topping out along here during a qualifying session. I really shouldn’t get anywhere near that. At all. Obviously. I’m in a five-door family estate car on road tyres, not slicks. It weighs over half a tonne extra, and although it has more grunt than a car adhering to race regulations, there’s still a significant power-to-weight deficit.

But what’s this? One last glance at the speedo before I throw the anchors on: 151mph.

Whichever way you cut it that’s an impressive showing from the BMW M3 CS Touring. It’s a slightly lighter, slightly more powerful, track-focused take on the M3 Competition Touring – a car we know to be astonishingly good and easily one of the best all-round performance cars on sale. How does BMW top that?

It starts with a chunky price hike. The M3 Competition Touring can currently be bought for just under £92k, whereas the M3 CS Touring comes in at just over £126k. Ouch. The CS (Competition Sport) badge no doubt has good pedigree – the F90 M5 CS is arguably the greatest M car of all time – but a quick look through the spec sheet of the CS Touring shows only modest-sounding changes.

At 1850kg, it’s 15kg lighter than the Competition Touring thanks to the use of carbonfibre-reinforced plastic. The curing ovens have clearly been busy, as the bonnet, front splitter, front air intakes, mirror caps and rear diffuser have all been replaced with lightweight parts.

Along with red contouring on the grille, badges and spoiler, and new forged star-spoke alloys finished in gold, these are the key visual changes. Pair them with the exclusive British Racing Green paint and you’re onto an all-time great combo.

Under the skin, BMW’s unlocked more oomph from the S58 3.0-litre twin-turbo straight-six. There’s an increase in turbo boost and a remap to raise power output from 523bhp to 543bhp. Torque stays the same (479lb ft from 2750 to 5950rpm), but the 0-62mph sprint time is cut by a tenth to 3.5sec.

On the wide open and brutally fast Thruxton curves the straight-line speed doesn’t feel that different from a Competition Touring’s, but the corresponding level of excitement has taken a step forward. For a twin-turbo engine, response from the accelerator is about as crisp and predictable as it gets, while the frantic, brawny aural accompaniment has been dialled up. 

Part of this is down to the upgraded M-specific exhaust system that utilises electronically controlled flaps and a titanium silencer. It’s most noticeable on start-up, whereas on the move the change in cabin volume feels like it’s largely down to piped-in sound. An E46 M3 CSL at full chat it ain’t, but it sounds good enough that you’ll want to push it to its 7200rpm redline, which is a lot of fun but largely unnecessary given the levels of torque on tap; short-shifting feels key to a good lap time.

The ZF eight-speed automatic gearbox is a revelation. A controversial replacement to the DCT on this generation of M3, the torque-converter system was – on early G80 models – a little laggy. In this CS, it has all the politeness of a sophisticated auto when you want it and aggressive, snappy upshifts when you don’t. Arguably a dual-clutch would be better suited, but for a car with this road and track dual mission the balance feels just about right.

It’s very unlikely we’ll ever seen an M3 CSL Touring model, so this will be as extreme as BMW’s 3-series wagon will ever get.

There are also chassis upgrades, and like the engine mods they’re quite subtle, if more wide-ranging. Spring rates are up by seven per cent at the front and 11 per cent at the rear, with a revised damper tune and new auxiliary springs – partly to take advantage of the track tyres, no-cost option Michelin Pilot Sport Cup 2s on this car.

The steering, active M differential, all-wheel-drive system and brake control have all been modified to work with the updated chassis and tyre set-up, and to improve driveability. Cast aluminium M strut braces under the bonnet further increase rigidity, while the spring rates of the engine mounts have been stiffened.

You could argue it’s not £34k worth of improvements, but it takes only half a lap of Thruxton to make it clear the CS Touring is far more than the sum of its parts. This is a long, heavy car in the context of a racetrack but it does an almost flawless job convincing the driver otherwise. Thruxton may be fast, but it also requires precision and clean exits to carry speed. Cars this size are prone to roll over their outside wheels and wash wide of the ideal line. But while the CS Touring still requires caution, its ability to turn in, settle and hook up is outstanding.

It’s an aggressive, pointy set-up but one that feels like it’s been properly dialled in over thousands of hours on road and track for excellent driveability. It’s faster than the Competition Touring around a circuit (by 5.5sec at the ’Ring), but it’s the improved responses and nailed-on front end that make it so enjoyable.

Turn in at speed and there’s more conviction to the way the front end responds and deals with any mid-corner bumps. It’s confidence-inspiring in a way very few cars – let alone estate cars – can achieve. That said, much of the actual feel of what the car is doing is through the seat. The steering on the CS Touring is lighter than ideal for track use and ultimately does rob a layer of feedback, regardless of what setting you’re in.

Just like in the Competition, the CS’s steering response is one of many settings that can be customised, along with engine mode, gearbox aggression, damping and braking. BMW’s drive-mode configurability is without doubt one of the best in the game, in terms of how much choice the driver has, and how much difference the settings make.

For example, switching from an all-wheel-drive setting well suited to fast road use to a much wilder tyre-toasting rear-wheel-drive configuration with adjustable traction control is done in the blink of an eye, giving the car a significantly different personality. The M3 CS Touring on track offers the potential for a degree of fun seldom – no, scratch that – never seen before with a roadgoing estate car.

Full disclosure: our track driving was done on the Cup 2 tyres and optional (around £9k) carbon brakes. Sure enough, after 20 laps or so, the front left tyre was blistering badly. It’s a common issue for anyone lapping Thruxton hard, but it raises key questions about the CS Touring. How many customers will take their car on track, and how often? If that phenomenal on-track performance comes at the expense of on-road ability, doesn’t that defeat the inherent point of a fast estate?

Make no mistake, this can be driven and used like any 3-series estate. Interior tweaks are moderate – a lovely M alcantara steering wheel and heated M carbon bucket seats – and retain the decent legroom and boot space (500 litres with the seats in place) of the Competition Touring.

And what of the on-road ride comfort? The M3 is a firm car and never quite has the flow over bumps of cars like the Alfa Romeo Giulia Quadrifoglio, so the prospect of even stiffer spring rates feels like a daunting one.

Not so in reality. We’d have to put them back-to-back to be sure, but the CS Touring’s revised damper tune has greater flow and control at high speeds and, if anything, slightly less edginess at low speeds than the Competition. The CS Touring feels taut and composed rather than harsh and crashy.

Clearly, there’s plenty of range in the adaptive damper settings. While Sport+ still feels like overkill for the public road, Comfort delivers a well-rounded, usable setting at the expense of a little response and body control. It’s small gains over the Competition Touring, but the extra polish is welcome even if road noise is still on the high side.  

What’s more, the calibration of the power steering is more at home on road. Feedback remains average, but at lower speeds the delicate touch and immediacy of the rack gives a super-positive, lightweight feel to the front end. Coupled with the low, involving driving position it means the CS Touring is a highly enjoyable car at the energetic cruising pace of a good road drive.

That’s also where the ZF ’box confirms its value. A DCT transmission simply couldn’t match the docile verve of the single-clutch slushmaster when driving around town, and the breadth of ability suits the estate’s personality so well. A dedicated button – an actual physical button – to adjust the gearshift setting is also welcome. The most aggressive mode, while delivering fast shifts, gives an abrupt and exaggerated lurch during every up-change. Okay on track, not so much on road.

In their sportiest settings the gearshifts, carbon brakes and dampers are the three areas of the car that are a little too much for the road. Braking power is truly awesome and the ABS shows valiant restraint, but the pedal could be more linear. It’s easy to scrub off lots of speed at the top of the pedal’s travel but modulation thereafter takes some adjusting to. At £9k the brakes are pricey and – if you’re not using the car on track – arguably unnecessary.

This is one example of the questions a potential CS Touring buyer needs to address. It is, without doubt, the best track-ready estate car on sale today – possibly of all time – and a notable step on from the Competition Touring. It goes, stops, corners and thrills in a way that goes so far beyond its ‘box on wheels’ roots you cannot help but doff your cap to Munich’s M division.

And perhaps more impressive still is that it doesn’t ask for any on-road compromise to achieve this. If anything, it’s gained a touch of focus and finesse.

Yet for those unlikely to take an estate car on track – who, let’s face it, must be most of us – it’s hard to make the case that the on-road improvement justifies the additional cash (nearly 40 per cent more) over the already exceptional Competition Touring.

Look back at previous Competition Sport products and you’ll find instances where M has taken the other path. While the F90 M5 CS, for example, gained ability on track, it is revered for the vast improvement in its roadgoing prowess. It transformed an already strong M5 and sent it into orbit with upgrades that could be enjoyed on every journey.

In contrast, you really need to venture beyond the public road to understand why the CS Touring is a five-star car. Its value is best appreciated at Brands Hatch rather than on the B660, and for an estate car – even a quick one – that’s unusual.

Regardless, it’s hard to deny that where Audi once ruled, BMW’s domination of the fast estate market is now beyond question.