Just this week, our spy photographers caught BMW testing what appeared to be a prototype of a new M8 CSL with aggressive, motorsport-style aero. But that isn't the only BMW getting the CSL treatment. Back in April, we got our first look at the new hardcore BMW M4 undergoing testing, which we think will also sport the legendary suffix.

As testing of the M4 CSL continues, our spies spotted a new prototype parked with less camouflage, exposing the grille for the first time. Sadly, the M4's gigantic maw hasn't been downsized, but the CSL has different inserts to distinguish it. The prototype also has a more prominent front spoiler and special M design headlights (hence the camouflage on the lens).

While the new design direction has caused a lot of controversy, the M4 Competition's performance is undeniably impressive thanks to a 3.0-liter twin-turbocharged inline-six pumping out 503 hp and 479 lb-ft of torque.

BMW's CSL cars represent the pinnacle of M performance, so expect the new M4 CSL to be the lightest and fastest version of the sports coupe yet. Allegedly, BMW will crank up the M4's inline-six to produce 540 hp, while significant weight reductions such as new carbon components and removing the rear seats will make the CSL even faster. For reference, the regular M4 Competition will sprint from 0-60 mph in 3.4 seconds.

Unlike the regular M4, the new CSL will reportedly only be available with rear-wheel drive and a six-speed manual transmission. The last M model to wear the legendary CSL badge was the 2004 BMW M3 CSL.

This will be the first time the M4 has ever been given the CSL treatment. Reports suggest it will enter production in July 2022, so we can expect it to debut online a few months earlier, possibly at the 2022 Geneva Motor Show in March. Expect production to be extremely limited just like the previous-generation M4 GTS; BMW only made 700 examples.