[ErickC]

I first noticed this bug when I updated to the most recent Monogame build a few weeks ago, and it's present in the latest unstable builds as well. OR is not following the throttle RPM schedule as outlined in the diesel engine block. When you reduce power by one notch, the RPM will stay wherever it was at the last notch. The power at the wheels will decrease to the appropriate output. When you reduce power again by another notch, the engine speed will drop, but not to where it is supposed to be. The only way to obtain the right RPM at the right notch is to throttle up again. The problem gets worse as speed increases. This worked fine in all builds before the diesel model changes.

Corrollary to this is a perpetual wheelslip indication and erroneous power readings (i.e. greater than zero) for for locomotives that are unpowered (such as cabooses that are specified as locomotives to use a 3D cab).

[steamer_ctn]

This functionality did go missing for a while, but should now be back in the latest unstable version. Generally there is a small time delay for any changes to flow through from the unstable version to the MG version. So it is always best to check these type of issues in the unstable version first to see if the issue is still current.

I have done a quick test with my test stock, and it appears to be working ok in the latest unstable version.

Can you please recheck the outcome with the latest unstable version, and my test stock and confirm whether problem still exists or has now been corrected?

If you believe that it still exists in the latest unstable version, can you send me the log file, and describe the testing scenario that you used with the test stock so that I can reproduce the issue in my test environment.

Thanks

[ErickC]

I am using U2020.02.16-0106. Your test locomotive doesn't have a ThrottleRPMTab, and I should note that all locomotives lacking as such work just fine. The problem I am experiencing is with my own GP7 and GP9 locomotives (the same ones I sent). I was going to retrofit them with tractive effort curves to see if maybe this might solve the problem. I should also note that all of the other problems I was having with previous builds are now gone in this build, and everything seems to otherwise work great.

I am considering the possibility that it may be related to the nonlinearity of the throttle. As is correct for EMD locomotives, the engine speed in Run 1 is the same as idle (actually, it decreases slightly, which is generally what happens in the real world as load is introduced), with engine speed increasing in Run 2 through Run 8 (the amount per notch depends on the locomotives, with the 567C in the GP9 topping out at 835, and the 567B in the GP7 topping out at 800).

EDIT: I just ran a test where I retrofitted the throttle notches and an ORTS diesel block containing only my 567B RPM tab to your test locomotive, and it responds to the throttle exactly as it should. Something in the current GP7 and GP9 physics is what's causing the issue, but I'm at a loss as to what it might be. The next step was to add the whole 567B ORTS diesel block from the GP7 - with the whole block, the locomotive now has the throttle problem. Systematically, I deleted several blocks of data to see which might be the culprit, since an OR diesel block containing only the RPM tab works as it should:

-Removing the diesel torque table does not solve the problem
-Removing the fuel consumption table does not solve the problem
-Removing the diesel power table crashes the sim
-Removing the rest of the variables does not solve the problem

I suspect that the culprit is an interaction between the throttle RPM table and the diesel power table, however, it can't be tested because you can't remove this table without removing everything but the RPM table.

EDIT 2: I have isolated the problem.

-You can remove the diesel power tab if you also remove the diesel torque tab. This does not solve the problem.
-Removing the maximalpower parameter does not solve the problem.
-Removing the diesel power tab (along with the torque tab) and the maximalpower parameter solves the problem. However, then the power curve will become linear, which is not correct.

[steamer_ctn]

I have tried running your GP7 #381 unit, and I can't see any problems with its operation, as the units rpms seem to go up and down as the throttle is moved.

Which GP7 unit were you experiencing the problem with?

Can you give me a step by step test scenario so that I can see what you are seeing?

Thanks


EDIT: One thing that I notice in the INC file is that the RpM change up rate is a lot faster then the change down rate, so it will take longer for the rpm to drop, then rise.
The fact that the TAB is non-linear should not make any difference.

[ErickC]

All of the GP7s use the same include file for the engine parameters. All I am doing is starting a train and moving the throttle from notch to notch as the speed limit and terrain demand. When the locomotive is stationary, the throttle does exactly what it should. But any locomotive with an ORTS engine block that includes both the maximalpower parameter and the diesel power tab (with its associated torque tab) exhibits the same behaviour when the train is in motion, and the problem gets worse with speed. It really becomes noticeable above 18 miles per hour or so. This includes your test locomotive when the data is added, even when the change up and change down parameters are deleted. Only deleting both the maximalpower parameter and the diesel power tab eliminates the issue.

The slower power down is correct. A 567 throttles up slightly faster than it throttles down. When the offending parameters are removed, the engine responds as it should.

[steamer_ctn]

Ok, I now see the issue that you are raising.

I will look into it.

[ErickC]

Excellent. It's been really vexing because I spend most of my in-sim time switching, which means a lot of rapid power changes. I put a lot of effort into the audio, so it's been sounding really funky around here lately.

[steamer_ctn]

I have identified what was causing the issue.

It was a piece of (pre-existing) code that was comparing the diesel engine output power with the rail hp. If the rail hp exceeded the output power then it would hold the RpM at this equivalent value.

I don't understand the logic behind this code and the reason for it inclusion, as it would never be expected that rail hp should exceed the diesel output power, provided power settings are correctly set.

For the time being I have disabled it in a patch just uploaded to the unstable version. Please check and confirm that this corrects the issue that you have raised?

If anybody is able to shed any light on the purpose of this section of code, I would be happy to hear from them.

Thanks

[ErickC]

Everything is right as rain in U2020.02.19-0151. Very odd. I had a weird feeling that it was something along those lines, I noticed that rail power was exceeding output under certain regimes and it seemed to coincide with the problem. At some point in the near future, I am going to generate tractive effort curves for all of my existing OR units, compare your demo units to mine, and do some more pruning and adding of parameters as necessary. I hate issuing patches, but I think people will be pleased with what they get for their trouble.

[steamer_ctn]

ErickC, on 18 February 2020 - 07:04 PM, said:

Everything is right as rain in U2020.02.19-0151.

Thanks for the feedback.

ErickC, on 18 February 2020 - 07:04 PM, said:

At some point in the near future, I am going to generate tractive effort curves for all of my existing OR units, compare your demo units to mine, and do some more pruning and adding of parameters as necessary. I hate issuing patches, but I think people will be pleased with what they get for their trouble.

It shouldn't be necessary to go to the effort of developing traction force curves, unless you really want to do it.

I will be interested in the outcome that you achieve.

I am particularly interested in how you have set up the prime mover, as this is still a grey area for me at the moment.