According to Autocar, the engine is a further development of the new turbocharged 2.0-liter four-cylinder developed by AMG for its future compact car range. In the upcoming A45 AMG and CLA45 AMG models, this 2.0-liter mill will deliver more than 330 horsepower and 295 pound-feet of torque.
The 4.0-liter V-8, meanwhile, should deliver more than 450 horsepower in its base form. Higher states of tune could see the engine pumping out closer to 600 horses!
It will replace the current naturally-aspirated 5.5-liter V-8 found in the SLK55 AMG in AMG’s future, turbocharged engine hierarchy: the 2.0-liter forms the base and is followed by this new 4.0-liter V-8. Further up the ladder is the 5.5-liter V-8 and 6.0-liter V-12 found in a number of current AMG models.
Sadly, it looks like AMG's venerable 6.2-liter V-8 (pictured above) is on its way out.
If the report proves accurate, look for the 4.0-liter V-8 to debut in the 2015 Mercedes-Benz C63 AMG due out next year.