After the original 3.0 CSL and M3 E46 CSL, the M4 CSL is BMW's third-ever Coupe Sport Lightweight. Come to think of it, the official name has been changed to Competition Sport Lightweight with the new hardcore G82 model. As part of its festivities to mark 50 years of the M division, the German luxury brand unveiled last week a bunch of never-before-seen concepts. Now, Top Gear had the opportunity to get up close and personal with two of them.

The M3 E46 CSL seems awfully familiar at a first glance, but a closer look at the front bumper shows two intake holes rather than just one. Firing up the engine is a dead giveaway about how special this one-off project is since the sound doesn't come from a straight-six. Instead, BMW's engineers managed to cram in the larger 5.0-liter V8 from the M5 E39. It's a fully functional prototype that has covered a respectable 10,000 kilometers (6,213 miles).

Secret BMW M CSL Prototypes

While the standard M3 E46 CSL had 360 horsepower on tap, this one-of-a-kind car was substantially punchier courtesy of a 4.9-liter S62 engine replacing the original 3.2-liter S54. It's worth mentioning this wasn't the only V8-powered E46 as BMW also built a two-seat M3 GTR road car as a homologation special with loads of carbon fiber and 380 hp on tap. However, only 10 were ever made in 2001, so most of us remember it from Need For Speed: Most Wanted.

Top Gear then moves on to the M2 CSL, which died in its infancy as BMW's head honchos decided to green-light the M2 CS instead. The most obvious change is noticeable at the back where the engineers added a manually adjustable carbon-fiber rear wing with 3D-printed pillars finished in red. The coupe also received other bespoke aero and carbon upgrades, along with carbon-ceramic brakes.

When inquired by Top Gear magazine, BMW refrained from talking about the engine upgrades the M2 CSL could have received had it gone into production. However, logic tells us technicians would’ve pushed the straight-six engine beyond the 450 hp of the M2 CS while shaving off roughly 100 kilograms (220 pounds).

It's too early to say whether the upcoming M2 G87 will receive special treatment, but with BMW saying this will be its final M car powered solely by a combustion engine, hopefully, there'll be a CSL further down the line.

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