Minecraft wiki entry for Minecarts, associated text: Thereafter, the optimal spacing of powered rails on a level track is to use 1 every 38 blocks for occupied carts (that is, a repeating pattern of 1 powered rail followed by 37 normal rails, then another powered rail, and so on) which maintains a constant minecart speed of 7.97 m/s. If gold is in short supply, it is possible to use powered rails with more space between them at the cost of reduced overall speed (see above). If you definitely must have the full 8 m/s you should place a powered rail on a level track 1 every 34 blocks for occupied carts.[2]