As a young amateur engineer, I considered the traditional internal combustion engines too large after comparing its combustion volume and the total volume it demands inside a car. It is approximately 1:25-50, which means we need a space of 40 to 70 liters under a hood for a common 1.5 liter engine itself. Then I came on a purpose of reducing the second unit of 1:25-50 to 5-10. Plus, traditional IC engines have many reciprocating parts which limit the maximum revolution, and also consume a considerable portion of output energy. After several unsuccessful efforts I managed to create my own engine that meets both demands: more compact and more rotary (works at the usual 4 stroke and same process).
I am going to give a little explanation of my own engine. It doesn't have reciprocating parts like pistons, connecting rods, valves, springs, and even a camshaft. Instead, it has a single central part that acts as a piston for all 4 chambers. It moves as a pendulum and two rotary tube shaped small gas controllers. It is incredibly compact and light. It's 4 stroke, but can be referred to 2 stroke as one chamber is used twice in one cycle (4 stroke - 2 cycle). It's approximately 5 to 8 times smaller than traditional IC engines with the same power, besides more efficient and considerably cheap to make due to the perfect weight (lightest) of its only non-rotary part (all-in-one propeller shaped piston) and other small parts. Cooling and lubricating is not an issue.
While all followers of the "Green World" are trying to replace internal combustion engines with electric motors, my engine will take a place under the hood of heavy vehicles, sport cars, super cars and all future vehicles, at least as an "additional engine" showing everyone how small a high performance IC engine can be!