By Christopher A. Sawyer
LiquidPiston, Inc. recently unveiled its X Mini 70 cc four-stroke engine, which has just two primary moving parts and a box volume of 6.6 x 6.2 x 5.4 inches. At an indicated 10,000 rpm the prototype produces 3.5 horsepower and weighs about 4 pounds. When development is complete, LiquidPiston expects the weight to drop to three pounds, and power output to increase to five horsepower at up to 15,000 rpm.
The engine design is based on a LiquidPiston-patented thermodynamic cycle and engine architecture that, in the past, spawned compact, low vibration, high-efficiency 40 and 70 hp compression ignition diesel engines. This is the first time LiquidPiston has paired its concept with both downsizing and spark ignition.