Hi Old.Professor,
Protosound 3 decoders by default use a different calculation for acceleration and deceleration rates. CV 3 and 4 don't do anything unless you turn on "PWM mode" using CV52. As you surmised, to get a shorter stoping distnace in the default SMPH mode, you enter a higher value into CV 54 (MTH deceleration rate). The default value is 64, which equates to 8 smph/second of deceleration. As Randy suggested, the max value is 255, which will give you a deceleration rate of 32 smpgh/second.
0 in CV4 means no momentum. So, that's as low as it can go. If MTH uses CV54, then adjust that. Higher number should increase the deceleration rate. They don;t say what the maximum value is, try 255, which would be the normal maximum for a CV. That should make it slow down at a rate of 32 smph per second.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I'm attempting to adjust the decelation on an MTH GG-1 so that it stops in a shorter distance. The manual page indicates that engine has MTH PS3.0 electronics. Changing the value in CV4 from the default value of 0 (zero) seems to have no effect. I noticed that CV54 is identified as MTH Deceleration Rate with a default value (decimal) of 64. The deceleration formula is given as 1/8*sMPH/s. I increased the value stored in CV54 and got the locomotive to stop in a somewhat shorter distance. Is there anything else I can do?