MRCs are a hit or miss, and sound very.... bad.
If you can find an older soundtraxx decoder (pre-tsunami), the sounds are decent (although not as good as the tsunami) and they are cheap enough.
The AC4400 has a FDL-16 and not a GEVO. The AC4400s are basically Dash 9s in a new carbody with AC traction motors since the Dash series only came in DC. The GEVO is a new prime mover, the 12-GEVO which is BASED on the FDL, but sounds different. Nobody currently makes a stock sound decoder with a GEVO-12, but Soundtraxx may be doing one since Intermountain is doing ES44ACs and DCs.
Here's a breakdown
For modern diesels, theres the Dash series. In the Dash 7 line, the designation is *##-7 where * is the truck (B or C, DD for export), and the ## representing the horsepower rounded DOWN to the nearest hundred. For example, a C32-7 was a 6-axle locomotive that put out 3250 horsepower.
After the Dash 7 series, the Dash 8 series and Dash 9 series was designated like this: Dash $-##*(W). The $ is the Dash line, the ## representing the horespower rounded DOWN to the nearest hundred, and the * for the truck arrangement. With the Dash 8 line, GE offered the option of the North American Safety Cab which would add a W to the end of a designation if the locomotive was equipped. For example the Dash 8-40CW was a locomotive in the Dash 8 line, generated 4000 horsepower, had 6 axles, and was equipped with the wide cab. Some railroads, not wanting to break with convention, or with CSX, which has a computer that can only accept a 6-character designation, used the Dash 7 method of designating their locomotives (such as CW40-8 or C40-8W)
Then, GE introduced the AC series, which was the Dash 9 with AC traction motors, designation is AC####CW (would have a -CTE on the end if there was weight added to the frame to improve traction. UP and CSX have ordered some with this option) The # represents the horsepower. For example, the AC4400CW was a Dash 9, which put out 4400 horsepower, had AC traction motors, 6 axles, and a wide cab. If the railroads wanted the DC version, they got the Dash 9. The AC6000CW is an exception. It is NOT a Dash 9 with AC traction motors. It is a locomotive with a German built HDL-16 prime mover (which was deemed a failure)
After the AC series, GE introduced the Evolution series which conformed to the (then new) EPA tier 2 emissions standards. By this time, standard cab (as opposed to the wide cab) locomotives were no longer available due to the conventional and popular use of the wide cab. Also, by this time, all new road freight engines have 6 axles as they work better and provide more tractive effort for the horsepower generated. Because of this, GE dropped the truck configuration and cab configuration letters from the designation. The new engines, with the GEVO-12 prime mover, which can generate up to 6250 horsepower (but in practice is governed to 4500HP max to cut down on wear and tear on the locomotives) The designation is ES##** where the ## is the horsepower (rounded DOWN to the nearest hundred) and the ** is for AC or DC traction motors as the DC version came out first.
I'm not too sure about UP or BNSF, but CSX had their engines delivered as ES44DCs generating 4400 horsepower, but later the software was changed to govern the prime movers at 4000 horsepower to save on maintenance costs. The new ES44AC-CTEs on CSX still generate 4400HP. Norfolk Southern had their ES40DCs delivered with 4000 HP, but they are buying AC engines now, with 4400 horsepower (ES44ACs). Some of CSX's AC6000CWs with the unreliable german prime movers were returned to GE and had their HDL-16 replaced with a 12-GEVO generating the full 6250 horsepower.
The MBTA just ordered 20 passenger locomotives with the 12-GEVO on board and will have them governed at 4650 horsepower for passenger service. (the extra is for the head-end power, and because passenger coaches are heavy!)
