A system and method of controlling maximum available engine power of a combine harvester wherein the engine drives the harvester and additionally powers a threshing mechanism for separating harvested crop into grain and crop residue and at least one further crop processing subsystem that may be selectively configured and disengaged, including a straw chopper engageable for chopping the crop residue and propelling the chopped residue from the harvester, structure configurable for directing the crop residue into the chopper or to bypass the chopper, utilizing a controller for automatically reducing the maximum available engine power as a function of the status of the engagement of the subsystems, particularly the chopper and the configuration of the associated structure.