...or is it other effect? Kinetic energy cap vanishing?
I've built a test setup: six powered rails on the bottom of a 40-block incline of unpowered rail, and a short loop of rail on the bottom.
If I ride in a cart slowly onto the powered rail, it pushes me near the top of the incline, almost all the 40 blocks and after descent back, through the powered rail, the loop and the the powered rail again I get ejected a long distance from the top of the incline, with a plenty of power to spare - as if energy from descent and double pass through the powered rail accumulated.
Now if I push an empty cart onto the powered rail, it goes some 10 blocks up, descends, then goes around the loop, and back, 10 blocks up. The same happens if I push the empty cart down from the top of the incline.
Similarly, if I leave a long span of unpowered track on the bottom of a long incline, I can ride a long way after the descent, but an empty cart stops a short way from the bottom of the hill.
I'd think such a blatant effect would get mentioned somewhere in the wiki. Or am I doing something wrong? Need to release brakes on empty cart or something?