PlayStation (major) Ac4400 Dynamic Brakes Behaving Incorrectly

Stujoy, maybe my question is redundant since the issue is on the road map but could you perhaps test the locomotive in full dynamic braking like this:

1. Stop the train on a grade that is higher than what the dynamic brakes can handle (using air brakes). Go into full dynamic braking while stopped and release the air brakes. The train should start rolling.

2. Record the klbf value on the HUD/MFD at maybe 5mph, 15mph etc (or in steps of 5mph).

This way it can be compared to real world values.

EDIT: The important thing is to have the dynamic brakes in notch 8 to avoid having to infer a maximum value.

 

I did that very thing as part of my testing, but didn’t write down the numbers because I didn’t feel the need due to what I observed. During that test the braking force was so high at low speeds that I had to keep releasing the dynamic brakes to get the train to roll faster than 1mph with braking force approaching 100klb at 1mph (All air brakes were fully released). I could get the train up to various speeds up to around 8mph (by releasing completely to get the speed to increase and then applying the DB again) but it would always slow down and the braking force would rise again as it did. If I let the train reach around 12mph, the train would then accelerate away, even in Notch 8, and the braking force would continue to decrease as the speed got faster (therefore increasing the rate of acceleration too) until there appeared to be very little braking going on at around 30mph. Again no numbers but a clear inverse relationship between speed and braking force. But just the massive braking force at very low speed was enough to show there was something very serious going on, that’s why I didn’t write the numbers down. The braking force numbers were the same on the MFD as they were on the HUD throughout.

 

So from what I have gathered, the 100 klbf at 1mph is not necessarily incorrect as the AC4400 has AC traction motors which can produce high braking force at very low speeds (check the SD80-MAC numbers you posted) but the early drop off at ~ 12mph seems to be too early since that would would imply a brake power rating of 3300 hp rather than 4400 hp. A more realistic speed for when the braking force decreases should be around 16-17 mph. After that point you would still see an inverse relation. You also mentioned earlier that you had around 90 klbf at notch 3 which also seems like a bug as that would imply something like 240 klbf at notch 8.
So basically If I understood your numbers correctly the bug is too low braking power but the overall form of the curve is not necessarily incorrect.

But I don't think the following statement is correct if you read the SD80-MAC numbers:
"But just the massive braking force at very low speed was enough to show there was something very serious going on"

Check this graph for the braking force vs speed for a SD60 and SD40-2:
https://www.tsb.gc.ca/eng/rapports-reports/rail/2001/r01w0007/images/r01w0007-figure-02.gif
The SD60 iirc is a DC locomotive (unless they ommited "-MAC", I could be wrong here though, it might be the AC variant) with extended range braking so it does not achieve max brake force at quite as low speed as an AC would, but you can still see that it is realistic for a locomotive to hit max brake force at low speeds, and you can also see that all locomotives would have an inverse relation for force vs speed at higher speeds (although not 12 mph, especially not for a powerful locomotive as AC4400).