From the parent article:<p><i>The new engine will meld the best characteristics of gasoline and compression ignition engines with an innovative piston architecture refined by Achates Power that sets two pistons moving in opposition in one cylinder. As the crowns of the pistons slide toward each other, they compress a mixture of air and gasoline to such extreme pressures that the mixture auto-ignites without the need for spark plugs in a process known as compression ignition.</i><p>which is the same principle as the deltic engine.