Liquid Piston gets more DARPA funding for 30KW engine 30 times smaller than todays engines

DARPA has awarded LiquidPiston an additional $2.5 million to continue development of its 30kW X4 rotary diesel engine prototype, bringing DARPA’s total funding of the engine technology to $6 million.

When development of the fully packaged engine is complete, the 30kW X4 engine is expected to weigh just 30lbs and fit into a 10” box, while achieving 45% brake thermal efficiency – approximately an order of magnitude smaller and lighter than traditional piston diesel engines, and also 30% more efficient. The efficient, lightweight, and powerful rotary Diesel/JP-8 X4 engine offers a disruptive power solution for direct as well as hybrid electric propulsion and power generation.

* it will be about 4-30 times less volume and weight than existing engines
* it will be about twice as efficient

It can be used for breakthroughs from drones, robotics and exoskeletons.

Lightweight and Compact

High power density – up to 2 HP/Lb (3.3 kW/kg)
30% smaller and lighter for spark-ignition (SI) gasoline engines
Up to 75% smaller and lighter for compression-ignition (CI) diesel engines


No poppet valves
Exhaust turbulence minimized by over-expansion; no muffler required


Only two primary moving parts, optimally balanced, resulting in near-zero vibration


20% decrease in fuel consumption possible for SI gasoline engines
50% decrease in fuel consumption possible for CI diesel engines

Multi-Fuel Capable

Diesel, gasoline, natural gas, JP-8


From 1 HP to over 1000 HP