Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The EMD GP22ECO is a 2,150 hp (1,600 kW) B-Bdiesel-electric locomotive rebuilt by Electro-Motive Diesel and Norfolk Southern's Juniata Shops. Initially EMD built two GP22ECO demonstrators, one based on a GP9 and one based on a GP40, but thus far all orders have been for conversions based on EMD GP40 and EMD GP40-2 series locomotives. The rebuild involves replacing the existing prime mover with an EPATier-II-compliant turbochargedV8710G3A, with Electronic fuel injection. The prime mover is mated to an AR10 alternator for traction power, a CA6 alternator for control power, and a computerized control system. Applying this to a 6-axle locomotive results in a SD22ECO. Some 6-axle locomotives could alternately be converted into a SD32ECO, using a 3,150 hp (2,350 kW) V12 instead.
When applied to GP40 or GP40-2 series locomotives, this conversion does not alter the external appearance of the locomotive, although the conversion of the GP9-based demonstrator required extensive changes to the long hood. The GP22ECO offers customers a 'factory' upgrade of existing locomotives.
Norfolk Southern's units were rebuilt from GP38AC units. They also feature electrical, mechanical, and emissions improvements.
References
David Lustig (July 2008). "EMD returns to re-power market". Trains: 24.
KCS #2820 post-rebuild with a "Retro Belle" paint job
