These engines are not the fastest, but they are the smallest and cheapest ones, two of them are made of 8 blocks, and one of them is a record breaking 7 blocks flying engine!
In the download there are also buttons and signs on the engines, when you press the button the engine will start moving and drop off the button and the sign on it. You can activate the engines in many different ways, all you need to do is to update one of the pistons. (block update is when a block changes near another block, causing it to check what's around it and interact with it)

Please let me know if you created a smaller version of these engines! I really want to see if it's possible to make them smaller, I will also add a link to your project if you upload the smaller engines to PMC.