For years, hydrogen cars have been hyped as the future of clean transportation. but quietly, something entirely different has emerged — a reinvented rotary engine that may outshine them all. What if we said that there is currently a solution to several issues that limit the improvement of piston engines, through a multi-fuel engine that is lightweight, compact, and adaptable to various scenarios?
Smaller, lighter, and smarter
Created by LiquidPiston, this compact and powerful prototype runs on various fuels and challenges everything we thought we knew about internal combustion. The X-Engine aims to be a game-changer: up to five times smaller and lighter than traditional diesel piston engines, but with fuel cell-level efficiency. unlike the older Wankel rotary engine — which never overcame issues like sealing, emissions, and fuel inefficiency — the X-Engine redesigns the concept from the ground up.
At the heart of this innovation is the High Efficiency Hybrid Cycle (HEHC), a new thermodynamic cycle that blends aspects of the Otto, Diesel, and Atkinson cycles. The result? Higher compression, more complete combustion, and larger thermal efficiency — leading to better fuel use and fewer emissions.
Even more impressively, the engine isn’t restricted to a single type of fuel. It can run on diesel, jet fuel, propane, hydrogen, and even high-proof vodka, showcasing remarkable adaptability. This flexibility makes the X-Engine ideal for multiple industries also being a valuable tool to help bridge the global shift toward cleaner and more sustainable energy solutions.
Fixing old problems with smart design
Rotary engines have long delivered smooth performance and high power-to-weight ratios, yet persistent design flaws held them back from widespread use. The Wankel engine, for example, faced chronic challenges with incomplete combustion, sealing complications, and inefficient lubrication systems.
LiquidPiston’s X-Engine promises to fix these flaws with a stationary combustion chamber, solving several challenges at one. Because the chamber doesn’t rotate, fuel injection becomes more precise, and the burn is cleaner. The chamber’s shape can also be optimized for different fuels, increasing efficiency further.
Another big improvement is stationary apex seals. Traditional rotary engines needed oil mixed with fuel to lubricate fast-moving seals — wasting oil and increasing emissions. The X-Engine positions the seals in the housing, where they’re easier to lubricate and seal more effectively, reducing both blow-by and oil consumption.
One engine, many fuel possibilities
The X-Engine’s true power might lie in its flexibility. It supports compression or spark ignition, depending on the fuel and application, and has already been tested with a surprising list of fuels — including gasoline, diesel, kerosene, jet fuel, propane, hydrogen, and for everyone’s surprise: vodka.
This adaptability is great news for basically all of the engine industry but has especially caught the attention of the aerospace and defense sector. Aircraft manufacturers need compact engines that work efficiently with the jet fuel and weigh little. The U.S. Department of Defense, on the other hand, enforces a single-fuel mandate for all its vehicles — mainly jet fuel — to streamline logistics across global operations.
Enter the XTS-210, a compact, two-stroke, 25-hp supercharged engine specifically optimized for both jet and diesel fuels. Compared to a similar-output diesel engine, it’s dramatically smaller, significantly lighter, and remarkably efficient, making it ideal for hybrid electric setups or mobile, portable power generators.
A revolutionary solution quietly emerged
While the whole world focused on hydrogen, a new rotary revolution was slowly taking shape. LiquidPiston’s X-Engine is compact, efficient, and versatile enough to change how we think about combustion engines. It might not just rival hydrogen power — it could rewrite the rules of clean energy altogether. In a future where flexibility and sustainability are key, this reimagined rotary has everything to lead the charge.
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