conrail_engineer wrote:...Fuel is used by the prime mover; and how much fuel it uses depends on LOAD.
Whether that load on the alternator is with two traction motors, six, or twelve (with a slug attached) isn't going to be drastically altered. What matters is how much weight has to be moved; and how much power goes through the traction motors to effect this.
Agree - it's basic physics.
Designers are aggressively attacking the question of fuel usage; and some of their solutions are surprising. The newest GEs, for example, seem to have only three positions on their electronic governors: About 400 rpm; about 800 rpm, and 1047 rpm (full throttle). All that's varied as the engineer goes through the notches, is the exciter; how much current is allowed to the traction motors.
I suspect this may done also to help meet Tier 3 emission requirements.
Turbocharged diesel engines – all current production locomotives - emit the most particulates (smoke) during the several seconds between the throttle is notched up and when the turbocharger “catches up” to the new higher RPM/load. (Classic example is the trademark Alco eruption of oily black exhaust when first throttled up.)
By reducing the number of possible RPM settings from 8 to 3, then grouping 2 or 3 throttle notches into each RPM setting, the frequency of RPM increases is reduced as the throttle is worked up and down. Hence particulate emissions will also be reduced.
Unfortunately however this doesn't make for as impressive trackside photos...