QuickEngine Builder is included to provide a quick method of getting a ballpark figure powercurve for an engine you may have in mind, as well as for entertainment. There are numerous sample engines in the menu to experiment with. While not complex enough to be used in the actual development and modification of real engines, it does provide enough variables to duplicate most real world power curves, and with enough practice, it's fairly simple to get within 10-15% of measured values. You can also study basic cylinder charging effects when changing intake valve closing points, as well as intake runner diameter and length, compression ratio, and displacement.
The rest of Straightline Accleration Simulator can use any power curves you generate with QuickEngine Builder when testing vehicle combinations.