My Northwestern Pacific fleet includes now an environmental friendlier engine. The new CLP60WTI4 built by the Rebuilder Calpower (California Locomotive Power) is right now on lease for evaluation.
According to the specs, it is a rebuilt SD60M with special upgrades so that the engine already meets the Tier 3 requirements and most of the Tier 4, way ahead of schedule. This would make it very attractive to smaller railroad companies. They could take advantage of the huge numbers of SD50 and SD60 engines that have been retired by UP and other companies over the last few years.
It still has the same amount of horsepower as the SD60 but with less fuel consumption and smaller amount of pollution.
Here are some pictures.