Jim Exler, Nampa, ID October 12, 2022
Ref: (TSU2 Diesel UG Pg 63)
When CV 10 is set to 0, the amount of load compensation is constant over the entire speed range, according to the value of CV 212. Setting CV 10 between 1 and 127 will determine the speed step at which the load compensation is reduced to 0. Setting CV 10 between 128 and 255 will select a partial load compensation reduction at full speed.
In general, you would want to have full load compensation at low speeds that will gradually reduce to 0 at top speed. Set CV 10 to 126 to achieve this. (See note on 128 vs 126 speed steps.) If you are using the Dynamic Digital Exhaust (DDE) feature, it uses the BEMF feedback to determine the effect levels and reducing the BEMF too much may affect the DDE output.
I have found after a lot of trial and error that I set CV10 = 0 and CV212 = 255 which is their defaults. I like a lot of DDE.
Note: Of the 128 speed steps, two are reserved for special commands such as Emergency Stop. This leaves 126 usable speed step commands to control the locomotive normally. Thus, any throttle or cab with a display will only show 126 speed steps at full speed and not 128.
Jim's methods: (use whole number values for percentage, not the decimal equivalent.)
To achieve zero cutoff at a percentage of full throttle, use this formula to find the speed step where the cutoff will reach zero.
CV10 (1-126) = (desired %) x 126 / 100 e.g., CV10 = 40 x 126 / 100 = 50This applies to both 28 and 128 (126) speed step modes, the decoder will interpolate the values.
Each step in 28 step mode represents 4.5 steps in 128 mode.
If you desire to set the minimum cutoff point at full speed to a percentage between 0 and 50% of the full throttle value, do this.A setting of CV10 to values between 128 and 255 will set the cut off at a percentage of full throttle between 0% and 50%. To find this CV value, use this formula. Not perfect but adequate.
CV10 [129-255] = (desired %) / 100 x 255 + 128 e.g., CV10 = 50% / 100 x 255 + 128 = 255 CV10 [205] = 30%, CV10 [192] = 25%, CV10 [179] = 20%
By combining CV10 with CV212, you can customize the BEMF intensity and cut-off. CV212 sets the maximum intensity and CV10 sets the point it is reduced to zero or to a point of 1% to 50% of the full speed setting.
Note: See the file "SndTrx CV212-10 settings je.xlsx" for a spreadsheet to calculate custom values.
CV212 intensity = CV212 / 255 e.g., 200 / 255 = 0.78 or 78%
BEMF intensity = CV212 x ( 1 - (speed step [128 mode) / CV10 )) / 255
| CV212 | CV10 | Speed Step [128] | Intensity @ half throttle | Intensity @ full throttle |
|---|---|---|---|---|
| 255 (100%) | 255 | 63 / 126 | 75% | 51% |
| 255 (100%) | 179 | 63 / 126 | 65% | 30% |
| 217 (85%) | 255 | 63 / 126 | 64% | 43% |
| 217 (85%) | 179 | 63 / 126 | 55% | 25% |
| 204 (80%) | 255 | 63 / 126 | 60% | 40% |
| 204 (80%) | 179 | 63 / 126 | 52% | 24% |
| 179 (70%) | 255 | 63 / 126 | 53% | 36% |
| 179 (70%) | 179 | 63 / 126 | 45% | 21% |
Two passenger cars probably isn't much of a load, depending on the motor type (if the motor/gear box provide a lot of torque). Another test would be to hold the loco while running, causing the wheels to slip... can you hear a change in the exhaust sounds as the wheels start to slip? Then, gently add a little more pressure to the loco with slipping wheels, loading the motor a bit more... can you hear a change? (Don't hold it for long... particularly is it has traction tires)
The change as the loco accelerates (I assume under control of the acceleration settings in CV3) from a stop is not be due to load, but rather the difference between the throttle setting and actual speed (measured by the B-EMF), adjusted by the throttle sensitivity setting in the B-EMF (s/b DDE) controls (CV 2.511). As the loco accelerates and this difference decreases, the loco exhaust sound will be adjusted by the decoder as you observed...
Another thing that I do, tho' it probably doesn't affect the sound, is set the B-EMF feedback cutout (CV10) to the approximate top speed step I run a particular loco at. IE: I run my 4-6-0s at a top speed step of 50-60 (with my speed table, this corresponds to 25-30 smph, unloaded on level ground) and CV10 is set to 50. Doing this gradually decreases the B-EMF feedback as the loco accelerates, and B-EMF reaches about 0 as the loco hits full road speed. When set this way, the loco will slow down on hills (unless you advance the throttle) and speed up on the down hill (unless you brake).