Questions Regarding Conventional Mode

I have the same issues. What is happening is that where the lock on is located is where the electrical current is most strongest. Though it should be even all the way around. Especially on layouts that are small. When the locomotive passes over this area, the flow of electricity appears to be almost surging, but in reality, it isn't. All the locomotive knows is that it is getting a strong current in the vicinity of that lock on and thus she may speed up a tad.

Is this harmful to the locomotive? No. Now if the locomotive takes off, really takes off fast each time, then yes this can become problematic for the locomotives motors. In my case, I ignore it and adjust the speed if necessary. I run in conventional mode as well, but with the remote. So, I can control the speed of the locomotive.

Actually, this problem/issue was way more pronounced when I ran G gauge.

Pete

On a 4 by 8 loop you should not see a dramatic slow-down/speed up due to having only one feed point on the loop, but installing a second feed on the other side of the loop would help stabilize speed.  What is happening now is that the power has to travel through a number of pin connectors between track sections to get to the farthest point from the feeder (that on the other side of the loop).  While the pin connectors between track sections are metal to metal, they often are not perfect conductors and present a smal amount of resistance to current flow.  Over several track section junctions, say six or more, you can see a volt or two or voltage drop under some conditions, enough to be equivalent to if you deliberately dropped the throttle on the power supply back a notch or two.  The train slows, then speeds up as it nears the feed point again and sees better voltage.  

Should you move on to building a permanent layout, soldering all the junctions, and installing a feed point every 12-20 feet or closer will assure virtually no voltage drop and smoother running.  

Note that trains will normally slow down noticeably in curves compared to straights and you might see this effect somewhat, although it is most noticeable when the straights are longer than the train, which normally is not the case with a 4 x 8 layout.  

Since you already have the Z1000, the DCS Remote Commander will allow you to run your PS-2 &3 engines remotely. It is plug and play with your Z1000. It's an inexpensive gateway to Command Control. The one limitation is the engines must have a Factory Reset. No biggie if your engines have never been run with DCS before.

Maybe Santa will drop one in your stocking.

Gilly

Thanks for the replies. Appreciate it. 

Perhaps I wasn't fully clear in that I don't see speed fluctuations when the trains are just running in circles. I do however see speed fluctuations when blowing the whistle and/or ringing the bell and that is what my questions above were directed to. 

I did install another feed and do see a more noticeable speed up when blowing the whistle in that area. I assume it is normal. 

I mostly see (or hear in the steam locomotives chuffing or increase in diesel engine sound) obvious speed up when ringing the bell and/or blowing the whistle in quick succession such as a crossing signal of long, long, short, long. Again, I assume normal? I think the proper term is DC Offset?

I have command control and have used it but after much headaches in getting it set up and working properly, I opted to go conventional. 

Speed up when the bell or horn button is pressed is normal on many different locomotives.  This is because to signal is an additional voltage to the track, but it's DC instead of the AC the trains use for motion.  Even with the difference, it's still an additional voltage on the track and thus the motors do see it and go a bit faster.