I feel as if calling this engine the most powerful production 4 cylinder ever should be followed by several asterisks. It is the most powerful series production 4 cylinder. The FQ440's 4B11T still remains the most powerful production 4 cylinder, and still has the specific output crown.
Ohhhh Germeezy, again! Welcome back, dear.
This engine from Mercedes-Benz is the most powerfull 4 cyl engine. Of course, we are talking here about normal cars, those that the auto companies produce for the normal market. Of course, you can find a more powerful 4 cyl engine for track, competitions, special purpouses, tunning, shows.... And I´m sure that the engine you are talking about is not the most powerfull 4 cyl engine builded.... sure there must be another more powerful.