FishOnOne wrote:
Ford went from 860 to 925 with just a tune and reports there's still plenty left from the engine/transmission design.
The Ford 6.7L changed to a bigger turbo to get there 2015 numbers of 440hp and 860 lb-ft. I have no doubts that they could not have gotten to that 925 lb-ft without that larger turbo either. The Cummins 6.7L went from 650 to 900 lb-ft without any mechanical changes to the engine.
If the old "there is no replacement for displacement" adage holds true power wise, the Cummins 6.7L is the biggest. However, I think they would need to step up to the added fuel pressure of the CP4 and the added precision of the piezo injectors to get there with emissions. They way those things are failing on the Powerstrokes and Duramax's, I would rather have lower power numbers.
Reputable tuners like Ryan Milliken and ATS have stated that the Cummins 6.7L(deleted and intake) can get up to a little over 500 hp/1,100 lb-ft at the wheels. That would be about 575 engine hp given a 15% drivetrain parasitic loss. The only thing holding it back is the turbos. Once you add bigger turbos and get to 700 hp, then it is the injectors and fueling holding you back.