LiquidPiston X Mini Engine Could Be the Smallest Range Extender

LiquidPiston X Mini engine 1 photo
Photo: LiquidPiston
Until we’ll benefit from the promised future batteries that are three times better than what we use now, we’re still going to optionally rely on range extenders for those longer electric vehicle trips. Some consider the best of their kind being the linear free piston engines, but do take a look at this little marvel from LiquidPiston.
The engine specialist company based in Bloomfield, CT, develops compact, powerful, quiet, efficient, multi-fuel combustion engines that are scalable from 1 to 1,000 hp. Their latest creation is the X Mini gasoline four-stroke rotary engine, which is no bigger than your hand, yet develops enough power to move a go-kart.

Right from the start, we’ll advise you not to believe this is one of those low-compression Wankel engine. It is indeed a rotary engine, but it works on a completely different way, having three combustions chambers and each firing in a full rotor revolution.


The engine uses a High Efficiency Hybrid Cycle (HEHC) combining the advantages of Diesel, Otto and Atkinson thermodynamic cycles, including:
  • high compression ratio and spark-ignition
  • a dwell near top-dead-center to force combustion occur at nearly constant-volume conditions
  • uses a larger expansion volume than compression
  • cycle-skipping power modulation to allow high efficiency at low power settings
  • possible use of water injection to cool the engine and also increase chamber pressure

What does all this mean in the real world?

The alpha prototype of the 70cc X Mini makes 3.5 hp and, after it will make it into production, it will make over 5 hp at around 15,000 rpm, while being quite silent and weighing only 3 lbs (1.4 kg). Also, it will be able to operate for 1,000 hours before maintenance is required.

All this makes the tiny gasser suitable for handheld outdoor power equipment, lawnmowers, generators, mopeds, drones and even electric vehicle range extenders.

Compared with other combustion engines in its class, the X Engine will sip 20% less gasoline, will be 30% smaller and offer one of the best power density of up to 2 hp/lb (3.3 kW/kg).

And let’s not forget that its simple construction, which you’ll see in the video bellow, allows for easy scaling and meet different industry requirements.

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 Download: LiquidPiston X Engine specs (PDF)


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