What Is The Difference Between A GP38 And GP40?

In the GP40, a 16-cylinder turbocharged version of the engine produced 3,000 horsepower. ... The GP38 was a 16-cylinder, non-turbocharged (Roots-blown) model that produced 2,000 horsepower, initially using a DC generator and later (in the GP38AC) using the same AR10 alternator as the GP40.