Depends if yoou are using 28 step or 128 step mode for control. I use Digitrax which defaults to 128 step and I always use it that way for finer control. There are less than 128 actual steps because a few are reserved as part of the DCC control packet, so middle is not 64, more like 63. Start is step 1, as I like my locos to just barely crawl at step 1. With 28 step mode, the middle would be 14.
But it's not just "at" that step. You are effectively drawing two lines through 3 points when using CV2,5, and 6. One from the CV2 value to the CV6 value, and one from CV6 to CV5. The flatter the line, the less change there is per step on the throttle, the steeper the line, the greater the change. One way to utilize this is to first set CV2 for best starting, and set CV5 so the loco goes a realistic maximum speed at full throttle - no 200mph steam locos, please. Then adjust CV6 based on the usage of the loco. A drag freight loco will spend more of its time running slow, so use a lower value for CV6 than would make a perfectly straight line through all 3 points. A passenger loco will typically get up to road speed quickly after each station stop, so in that case uses a higher value for CV6 than would make a straight line. What you get is a freight loco that has fine speed sontrol at the lower speeds, where it takes more steps to change from say 5smph to 15smph than it takes to go from say 30smph to 40smph, and a passenger loco that uses fewer speed steps to get from 5smph to 20smph than it takes go get from 40smph to 65smph. Slow acceleration but finer control when making pickups and setouts for the freight, fast acceleration and finer control at road speed for the passenger.
--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 do not think these CV values match up other than speed step 1. This is what I do:
Be aware that some decoders to not have CV5 or CV6. You will need to build a custom speed table. If you can get the speeds within 5 mph, you should have no problems consisting engines.
I have an AccuTrack II speedometer that I use to measure the speed of my engines when I program them. This is invaluable for 'speed matching'...
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Are there particular speed steps that are used for low, mid, high speed matching?