Like an RS badge to a Porsche enthusiast, CSL – for Coupe, Sport, Lightweight – is an adornment to deify for any BMW fan. But where these days a RS Porsche is an expected 911 variant, the CSL moniker has only ever graced two coupes from Bavaria.

To find the first, one has to wind back to the early-1970s; back before the now-legendary M-Division was formally formed.

While Phase III Falcon GT-HOs and XU-1 Toranas slugged it out in Aussie Series Production Racing, a battle royale was raging on the circuits of Europe. Ford’s Capri RS2600 had taken the European Touring Car Championship driver’s titles in 1970 and 1971, beating the ageing BMW 2002.

BMW’s response was the E9 3.0 CSL, a lighter and more powerful version of the achingly pretty 3.0 CS coupe. First unveiled at the 1971 Geneva motor show, with production cars delivered from mid-1972, the CSL would go on to win the 1973 ETCC, then enjoy an uninterrupted run at the top from 1975-79. But that’s a story for another day…

Fast-forward to the early-2000s and the M-Division was well established as a group who could take BMWs regular offerings and really amp-up the excitement factor.

The third-generation E46 M3 may not have been a homologation special like the original E30-series, but it had developed into a compact, fast, grippy and capable coupe; powered by a 3.2-litre version of BMW’s legendary naturally-aspirated straight-six.

In a nice piece of symmetry with that maiden ETCC victory, the M-Division decided to resurrect the CSL badge in 2003, this time on the rump of a limited-run road car.

Evoking the spirit of the E9, the M3 CSL was both lighter and more powerful than the model on which it was based. To achieve its final 1385kg figure – 135kg lighter than a regular M3 equipped with the SMG clutchless manual transmission – the CSL sported a carbon-fibre roof, like today’s M4, that saved six kilograms instantly.

The material was also used for the front air-dam and associated winglets, the rear exhaust valance and liberally throughout the interior (door cards, centre console). But perhaps the coolest application was found under the bonnet, where a massive carbon airbox was fed by a butterflied opening so large you could almost fit your head inside. It drew air from a hole cut out of the front bumper, on the left-hand side.

M engineers went through the CSL from back to front, using a thinner-walled exhaust system, aluminium rear control arms, thinner rear glass, a lighter boot lid (with elegantly-incorporated up-sweep to reduce lift) and fixed-back glassfibre front seats trimmed in cloth/Amaretta.

There’s only two, rather than three, seats in the rear, there’s no cruise control and niceties such as air-conditioning and a stereo were no-cost options.

To make the most of the weight reduction, the straight-six was modified for an additional 13kW and 5Nm, the peak of 265kW arriving at 7900rpm, with 360Nm torque at 4900rpm.

Changes to intake system and camshaft timing, along with revised exhaust valve geometry and the altered exhaust, are key to the engine’s increased output.

Linking to BMW’s Formula 1 involvement with Williams, the M3 CSL was available solely with the ‘Sequential Manual Gearshift’ six-speed automated manual. The link may have worked for the marketers, but it went against the otherwise uncompromising weight-saving mantra that CSL was built around; the SMG ’box weighed 25kg more than the conventional six-speed manual!

Braking – not a BMW strongsuit at the time – was taken care of via 345mm cast iron discs up-front, cross-drilled for lightness and ventilation and 20mm up on the M3’s. Rear discs remained the same at 328mm. Single-piston ‘swinging’ calipers were employed all-round.

Specifically-designed 19-inch CSL alloy wheels were available with a choice of tyres, both designed by Michelin. You could have Pilot Super Sports, or semi-slick Pilot Sport cups… though you had to sign a disclaimer if you opted for the latter, acknowledging you understood their ineffectiveness in wet or cold conditions.

Even if you were flush with funds in 2004 – when the CSL became available locally, though only 23 of the 1400 total build came here – the $210,000 ask was steep, especially when considering the standard M3 was $142,000 with either transmission.

On first approach, the E46 M3 CSL (kindly supplied by BMW Australia, who remains the sole owner of this example that rides on Pilot Super Sports and is optioned with air and stereo) remains visually arresting today. Its stance, hunkered-down with wide arches swallowing stunning alloys and its carbon roof glistening, is full of subtle menace. Then you note further carbon details and that intake slot, identifying the CSL to those in the know.

Lift, rather than pull, the door handle and you immediately note the Alcantara-trimmed wheel’s gear shift paddles and singular switch, used to activate a dynamic mode for the stability control system.

The fixed-back seat is bolstered stiffly enough to punish your back if you are the type that lands, rather than sits, in the seat, but once ensconced it forces an upright, cosseting driving posture that’s perfect for ultimate command over the CSL’s controls.

It is curious that there’s any rear seating at all, and the level of trim detail – even in the lined boot – seems at odds with the lightweight ethos, but the carbon door-trim eases the feeling.

Ahead of the stubby, console-mounted sequential gearshift sits three buttons, though the one to the right is perhaps the most intriguing. Simply marked ‘Sport’, it unleashes the CSLs feral side… but we’ll get to that.

Make sure the gearbox is in neutral, and twist the key. The CSL yawns into life with the requisite E46 M’s tinny idle slightly amplified by the thinner exhaust. Flick the lever to the right, and automatic mode is engaged.

There’s five ‘modes’ offered in auto, just like in sequential mode, and ranging from slurring shifts to maximum thump and bump brutality. Blend the throttle in so as not to overload the automated clutch and the CSL pulls away somewhat graciously as the engine takes up drive. If you’re not in a rush, the softest mode slurs quickly to sixth gear for economy, masking the engine’s ferocity with unexpected docility. It can do it, but it’s not what the CSL is about.

Slip the lever into sequential mode, up the shift speed, hit that sport button and the shackles are broken. Much has been written about the CSL’s sound, but in reality words can barely match the experience.

From under 3000rpm, full throttle reveals a slurping, gushing intake of air, not dissimilar to a classic British six on Weber carbs. Breach the 3000rpm barrier and a metallic resonance buzzes the cabin through to the 4900rpm torque peak. The bass then takes over, sounding almost V12 Lamborghini-like in pitch as the CSL hits stride, bursting with energy to 8100 revs.

Intoxicating can’t begin to describe it.

Sadly, the SMG box can’t keep up with the engine’s unadulterated wild side. It’s not that it’s overly slow in the most brutal mode, but it’s inconsistent. Sometimes, a slight lift of the throttle brings a sharp shift, but the next time you grab a gear the same trick sees the CSL fall out of the feral zone. Keep the throttle planted and a sharp thud kicks through the cabin; not something I’m keen to do in a car with only 8500km on the clock.

Arrive at a sequence of corners, however, and the paddles are welcome, the downshifts providing consistency and therefore confidence, with a delicious rev-match.

Braking for a tightening but smoothly-surfaced left-hander reveals progressive pedal feel but a lack of ultimate retardation, and a tendency to trigger the anti-lock brakes; no wonder many CSL owners upgrade to an AP Racing brake kit.

But from the first steering input on, it’s all smiles. The quicker rack (14.5:1, compared to 15.4 in the M3) allows an uncanny link between driver and front tyres, the CSL’s revised suspension tacking the front-end to the apex with complete accuracy and unfiltered feedback.

The road unravels before a third-gear right, allowing a brief burst of throttle, the chassis revealing an ability to adjust its line via small changes to steering or throttle. It’s with you every step of the way.

Short-shift to third, wait a second, then hear the mounting crescendo bouncing off the rock shelf. Flick the intuitive steering to tack the BMW hard into the lumpy right-hander, and once more the CSL is revelatory, the damping able to cope with small bumps softly, but dismissing larger oscillations with disdain before taking full power once more – the rear only hinting at oversteer; apparently the CSL is a natural slider, but we are on the road, after all…

It’s also deceptively quick. The bark initially feels more than the bite, but a glimpse at the speedo suggests otherwise.

We’re in rarefied air here. The CSL lives up to its legend, and then some.

The fact it was built by a manufacturer and came complete with warranty makes it even more compelling. But it’s pricing does make you wonder; today, you’d be looking at $80,000-plus for CSL ownership, where a standard E46 M3 could be had for under $30,000.

Perhaps it’s time for the motoring.com.au team to come up with project E46: manual with big brakes, tuned and stripped out?

Or perhaps we should simply bow to those three simple letters that makes this car so special.

2003 BMW M3 CSL pricing and specifications:
Price: $210,000 (when new)
Engine: 3.2-litre six-cylinder petrol
Output: 265kW/370Nm
Transmission: Six-speed sequential
Weight: 1385kg (Tare)