GE FDL Diesel Engines - installment No. 2

In our first installment, we noted that the differences between GE prime movers employed during the production of the Universal series are rarely discussed and gave as a matter of introduction the briefest of tables indicating what the letter submodels were and in which locomotives they were used. There are exceptions of course, and we'll go into that and more in some further detail in today's installment.

Keep in mind that there is not a lot of data to be found - but also know that we have practically all that CAN be found. While this description isn't all inclusive, it will probably be more complete than anything in print or on the net so far.

FDL-16A This is the engine that GE used to power the production U25 locomotives. It is known that there were further sub-variations of the model numbering that correlated to modifications; for example, the engine model given in manual GEJ-3814 is 7FDL16A1. None of the exact breakdowns are known as far as the sub-letter number designations and these are almost never seen. In general it's very safe to say that in any GE manual, drawing numbers E-9900, E-9900A and E-9900B cover the "A" model and that it was production standard during all of the U25 and U50 runs. There were numerous changes in the engine during this time- most important was a change in firing order that appears to have occurred between 2/62 and 5/63. Perhaps concurrent with this was a switch in orientation of master and articulated connecting rods; at some point during "A" production, the rods were changed from master rods in the right bank of the engine to master rods in the left bank; E-9900B reflects this change which occurred before 10-64. Also at some point during "A" production, small check valves in the oil passages in both master and slave rods were omitted; E-9900B is also the first to show this change as well. Another alteration in the "A" series was the change from individually replaceable, keyed camshaft lobes on the camshafts to sectionally replaceable camshafts with non-removable lobes and again E-9900B is the earliest to reflect this change; a GE service bulletin in our large U25B Maintenance Manual (issued to the NYC) indicates this change occurred 5-64. Sometime before 5-62 the early one-piece crankshaft was changed to a two-piece design and mounting of the vibration damper was altered. In 1-64 a low water pressure shutdown was added to the engine governor. In 2-64 the Elliott H-588 turbochargers began to be delivered with increased thrust bearing area to extend service life. Also in 1-64 improved radiator panels, with improved core and tube design began to be applied to new production U25 locomotives; there were two different types of improved design, both interchangeable with the original. These radiator units appear to have been designed to reduce leakage due to expansion and shock. In 2-63 a field modification order was issued to change the setting of the lube oil pressure regulating valve, and later all engine made after August 15, 1963 had a new style lube oil pressure regulating valve. In 6-64 a new style of engine and generator hold-down attachment was employed, designed to reduce transmission of shock from the underframe to the diesel engine.

FDL-16C No "B" series engines were used in domestic locomotives, although for reference it seems as if the reversal in location of connecting rod mountings (from one bank to the other) happened with introduction of the "B" series. The "C" series powered all locomotives of model U28 in the US; it also was employed on various pre-production, field-test locomotives built in the midst of, or in place of, conventional U25 locomotives prior to the official introduction of model U28. The most important changes on this engine are the alteration of the cylinder unit design to include a removable, steel head section that contains all four valves (two intake, two exhaust) and the injector nozzle. This head was bolted into the cylinder assembly. Also, the exhaust system was altered from a somewhat complicated design of individual pipes for pairs of cylinders to a single-pipe exhaust in which cylinders simply fed a large tubular manifold. Engine speeds for the "C" remained the same as for the "A" although of course there was the increase in rated power, from the 2500 HP for traction / 2750 gross HP of the "A" to 2800 HP for traction / 3050 HP gross for the "C." Increased fuel rack travel was employed with exactly the same fuel system top to bottom. The cross-sectional drawing for the FDL-16C is E-13461. Apparently, the new style of cylinder unit, with steel head, was designed to interchange with earlier "A" units so that it could be backfitted to U25 or U50 locomotives, although one manual notes that old engine frames should be checked for proper depth of bore clearance to ensure that the cylinder units would fully enter into and properly seat in the engine frames; some small amount of grinding of bosses in the frame was all that was needed in some cases to clear this up. It also appears that the "C" model (although it might have been the "B" first, for export) introduced a new style of cylinder liner. The new style - first shown in a manual actually for the U25B/U25C and included after E-9900B - had a jacket applied to the cylinder liner that GE would later describe as the "Belly Band" type of cylinder liner. This was essentially a modification to further reduce exposure of larger engine parts to water; on the A, none of the frame was exposed to water at all, but the inside of the cylinder assemblies along the bore formed the outer water barrier for liner cooling (the liner itself being the inner barrier.) On the "C" engine, or should I say on the belly band liner, the cylinder assembly was protected against water exposure because the cylinder liner now had both inner and outer surfaces to contain cooling water.

That's enough for now on this topic. Next time we'll introduce the FDL-16D that appeared with the U30.