Mercedes-AMG is rightfully proud of its little M139 four-cylinder 2.0-liter turbo. It's the most potent four-cylinder engine in mainstream production, generating 416 horsepower and 369 lb-ft of torque we get to enjoy in the CLA 45. It's a large part of the recipe that makes the A45 S that we don't get in the US one of the best hot hatches in the world, but, of course, people always want more. Renntech, down in Florida, is currently testing its tune to make absurd amounts of power, but the German tuning house Brabus has brought its new tune to market, and it comes with a warranty. It's new A45 S based B45 makes an absurd 450 hp and 406 ft-lb of torque.

The extra power is squeezed out by remapping the already AMG prepped 2.0-liter turbo engine, fitting a new airbox duct, and Brabus's BoostXtra adapter. According to the tuning company, the BoostXtra adapter allows the B45 to make blow-off noises like a race car. In our neighbor's dilapidated slammed Civic, we would mock that. In a 450-hp Mercedes based hatchback, we endorse it.

According to Brabus, the B45 hits 0-60 mph in 3.7 seconds, but the top speed remains limited to 168 mph. And, because it's Brabus, the B45 also has some chassis performance and interior upgrades.

Specially produced ten-spoke Monoblock wheels sport wider Continental summer tires, and Brabus has fitted tuned and height-adjustable sport springs. They can lower the car by zero to 30 millimeters to affect the center of gravity and add to the hot hatch's agility.

Inside the B45, illuminated stainless scuff plates with the Brabus logo can be added with 64 colors available to synch with the existing interior lighting. Brabus aluminum pedals and floor mats with the Brabus logo embossed are also available, but Brabus is always willing to customize as far as a customer is willing to pay.