An M4 with 543 horsepower has been developed to compete with Porsche's 911 GT3. Rich Report explores the performance of this car. 

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It has long been a tradition for BMW's M division to develop performance-tuned versions of the automaker's standard road cars, and over the years, machines like the M5 and M3 have earned a reputation for expertly balancing track prowess with daily driving comfort. Occasionally, BMW lets the M division loose to build cars like the M4 CSL, where performance takes precedence over balance.

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During the 1970's, the first Competition Sport Lightweight (CSL) model was introduced to the market in the form of the 3.0 CSL, which was a limited release homologation special that was created so that the svelte coupe would be eligible to compete in the European Touring Car Championship. There was no doubt that the 3.0 CSL race car would take home the series title the following year.

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Despite the fact that it had been more than three decades since BMW revisited the badge, the 2003 M3 CSL made up for lost time. This hard-core version of the CSL sports coupe is a hard-core version of an already beloved sports car. 

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Due to the use of lightweight materials and the removal of some of the creature comforts of the standard M3’s standard body, the CSL dropped more than 200 pounds as a result. Additionally, grip and power were both increased to make the car even more athletic.

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As a result of the M division's success in producing special edition M cars in the years since, none of them have been adorned with the CSL badge, until now. There are only 1,000 examples of the M4 CSL in the world, and it follows the template established by its predecessors. With carbon fiber used for the hood, roof and rear decklid, as well as some sound deadening material removed from the rear seats, the M4 CSL drops 240 pounds in weight versus its M4 Competition counterpart. 

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Additionally, unique carbon-bucket race seats, titanium exhaust system hardware and model-exclusive forged wheels were used to reduce weight. By combining these efforts, the M4's curb weight drops to 3,640 pounds. 

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Pilot Sport 4S summer tires are also available as a no-cost option, but the alloy wheels come wrapped in ultra-sticky Michelin Pilot Sport Cup 2 R road-legal track tires.

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The improved grip is complemented by a range of chassis modifications that are specific to each model, including stiffer springs, bigger sway bars, revised adaptive dampers, strengthened engine and transmission mounts and a new aluminum strut brace installed in the engine bay. 

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Compared to the M4 Competition, the CSL's center of gravity has also been lowered thanks to its 0.3-inch lower ride height, which means the CSL's center of gravity is also lower.

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CSL also comes with more power: Although the 3.0-liter twin-turbocharged inline six engine has the same torque figure as the M4 Competition, at 479 ft lbs, an increase in boost pressure and recalibrated engine software add 40 horsepower to the CSL. 

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As a result, the engine's grunt is exclusively sent to the rear wheels through an eight-speed automatic transmission, resulting in a zero-to-60 mph sprint in 3.6 seconds.

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M4 CSL's design is based on the M4's polarizing front end, but its kidney grilles are bespoke to the CSL and optimise airflow to the radiators. As a result, the overall look is significantly more aggressive and compelling thanks to the new front splitter, hood scoops, red accent striping and integrated spoiler on the rear decklid, which evokes the M3 CSL while providing extra downforce at speed. Yet, this motorsport-inspired machine does not seem outlandish at all.

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Similar to the M4, the CSL's fixed-back carbon race buckets have been developed specifically for the M4. A lever at the front of the seats allows for forward and aft adjustments, but a tool kit is necessary for height adjustments. As with the tires, buyers can opt for the easier-to-live-with option at no extra charge over the power-adjustable and heated carbon-backed seats on the M4 Competition.

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We immediately appreciate the track-ready seats once we're behind the wheel. With the revised exhaust system and reduced sound deadening, the engine comes to life with a sense of authority when you press the ignition button, while the hunkered-down seating position and exposed carbon fiber on the center console are clear indications of the CSL's mission: a track-focused monster with a license plate to rival the Porsche 911 GT3.

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Its raison d'être aside, the M4 CSL is quite agreeable when it's conscripted for more mundane driving duties. Although there is some road noise inside the cabin, and few can gracefully emerge from those aggressively bolstered carbon buckets, the seats are generally comfortable once you are seated.

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There are a multitude of performance settings available in BMW vehicles, including shift firmness, exhaust volume, brake pedal response, and steering effort, among others. As long as all adjustments are set to the softest settings, the car is as easy to drive around town as a garden-variety M4, albeit with noticeably stiffer suspension settings.

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At the end of the day, though, every moment spent puttering around is just downtime between lap sessions. The M4 CSL didn't get a chance to be tested on a track, but an extended drive up Highway 74 in Palm Desert, Calif., gave us an idea what it was capable of.

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Even in Sport mode, the electrically assisted variable-ratio steering lacks meaningful feedback, and the effort remains too light for our tastes. However, thanks to the tenacious mechanical grip and the chassis with plenty of negative camber, turn-in is almost instantaneous and precise.

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With every successive corner, we press harder and dip deeper into the loud pedal every time the road straightens out, held in place by those gnarly race buckets. BMW's CSL power rating seems conservative, and we wouldn't be surprised if independent testing revealed that the CSL has an additional 60 horsepower that isn't mentioned on BMW's site. The standard carbon-ceramic brakes provide plenty of fade-free stopping power, so we're not complaining.

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Powered by an eight-speed automatic transmission, the car sprints to 60 mph in 3.6 seconds, and reaches a top speed of 191 mph. Uwe Fischer, courtesy of BMW.

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Inevitably, at $139,900, the starting price is nearly twice as high as an M4 Competition's base price. When a vehicle has its performance limits set at this high, public roads can only tell a part of the story. Every indication points to a machine that has many more thrills to offer when set loose on a closed course, for those few lucky enough to get their hands on one.