Rich_S wrote:Kali wrote:I have read ( obviously I've never driven one! ) about dash7 or dash8 series taking 2 mins or so at least to get usable tractive effort. Two-stroke EMD engines were more responsive anyway, and secondly EMD turbos are physically driven by the engine at lower notches ( technically making them superchargers at that point, I guess ) so there's much less waiting around.
Dash 8's are not that slow, if it's taking 2 minutes to load there is a problem. Now if you wipe the throttle, yes it may take the governor 2 minutes to allow the diesel engine to reach full RPM's.
Yeah, the 2 mins was from idle -> enough on the ammeter to get the train shifting; been investigating uboats a lot, they dropped all the current every transition which must be just wonderful on a steep hill, jeez.
Rich_S wrote:I don't know if I'd say EMD's are more responsive because of their Turbocharger. Of course that was always a selling point with EMD, "Every stroke is a power stroke", but if that is the case then why do the EMD 710's load at just about the same time as the GE's Cooper Bessemer 4 cycle?
Pass! I presume it's electronics & emissions stuff... the Jenbacker engine in the 70s loads really quickly with the same control system as the GEVOs, so I presume it really is down to engine design. Admittedly the 70 is 3700bhp.
Rich_S wrote:Not sure what Al Krug is talking about? but from everything I've seen thus far, each notch on the throttle still has a set RPM for the diesel engine speed. Al maybe confusing diesel engine RPM with main generator control.
http://www.alkrug.vcn.com/rrfacts/dash9.htm if you want to argue with him :) I will listen to anyone.
Rich_S wrote:EMD's have a device on their newer units called a chopper. Basically the computer can control the field of the main generator using gated diodes, so in theory you can be at a lower throttle notch, but if the computer senses a higher demand, it can gate the diodes for a longer period of time creating a higher output from the main generator. GE's have the same thing, but I always liked the name of the EMD device, sounds cool
Other name for a thyristor ( it's an AC transistor more or less ) - it's how you control AC traction motors too. Chopper is still the best :)