The Micro Cirrus 4-cylinder inline engine (water-cooled) was designed by Merritt Zimmerman in 1974. The 1/12 scale models were built in Ukraine, 2001 and 2003. This engine is 5″-long, 6″-wide, and 4″-high.
Two variations of the model Cirrus engine include these micro engines from Ukraine. They run on methanol with glow ignition and are among the smallest multi-cylinder 4-cycle engines in the world. The custom glow plugs are only a 5mm hex with a 3.5mm thread. The engines are less than 4 inches long and have a mere .5cc displacement in each cylinder, making the 4-cylinder only 2cc and the V8 only 4cc total displacement. Initial test results proved these micro engines would spin their 7- and 8-inch propellers to 13,000 revolutions per minute.
Only 25 of the 1/12-scale 4-cylinder air-cooled engines were produced in 2001 and another 25 of a water-cooled version. In 2003, the remaining parts for the 4-cylinder engines were used to manufacture less than a half dozen each of the air-cooled and water-cooled V8 engines.