How does the Super Awesome Micro Project work? I've recently read an article about a car which is made entirely of LEGO and it runs on air. I'm curious about how it works. Can someone explain the details of it?

Here is the car:



These are all the details I have:


  Super Awesome Micro Project is: A car made of Lego, that drives, has
  an engine made from Lego which runs on air. (wheels and some load
  bearing elements are non-Lego)
  
  Super Awesome Micro Project Factoids
  
  
  More than 500,000 LEGO pieces were used.
  The car engine is made from standard Lego pieces and runs on air!
  The engine has four orbital engines and a total of 256 pistons.
  Top speed is not very fast, around 20-30km
Assuming that you're asking about the engine in particular, it seems to be a large number of pneumatic engines that have been coupled together in order to supply the required torque. LEGO pneumatic engines typically consist of a pneumatic cylinder driving a crankshaft. Here's a basic picture to give you an idea:



The shaft usually also controls a pneumatic valve that switches the direction of the piston to allow continuous rotation as shown here:



This allows the engine to run on air pressure being directed to the pneumatic valve without the use of any electrical components.

These images come from a fairly simple single cylinder pneumatic engine by nico71 on Rebrickable that includes instructions if you are curious about more of the details of how these work, or if you would like to build your own.