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LiquidPiston’s Combustion Engine

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Based out of Bloomfield, CT, Liquidpiston designs and develops compact, high efficiency, high power to weight, quiet, and low-vibration multi-fuel internal combustion engines. With a horsepower output range from 1hp to over 1000hp. The team continues to do R&D out of their very own state-of-the-art facilities specifically designed and tailored to creating their LiquidPiston engines.

Among many attributes these engines have, the first that comes to mind is the engine’s award-winning efficiency. As EV vehicles progress combustion engines will naturally see a decreased demand. However, the team at LiquidPiston has created an innovative technology that may just prolong the life of internal combustion engines. It may appear to be loosely based on a rotary engine but the similarities end at the surface.

LiquidPiston's Combustion Engine

combustion cycle graph.

LiquidPiston’s power density –

With a power density of close to 2hp/lb, these engines pack similar power-to-weight ratios to full-on superbike race engines. The 30% smaller footprint along with high efficiency and reduced vibration is impressive considering the power output. Plus, these can run on a variety of fuel sources from diesel to gasoline with a few in between. With no valve train and exhaust designed to result in turbulence reduction, these engines are capable of record-setting noise level records. These same attributes also contribute to the massive reduction in engine harmonics and vibrations. Compared to a gasoline engine of the same horsepower output you can expect to see a 20% decrease in fuel consumption. The diesel counterpart will see a whopping 50% reduction in fuel consumption.


LiquidPiston's Combustion Engine

LiquidPiston’s visual combustion cycle.

LiquidPiston’s Combustion cycle –

At the heart of LiquidPiston’s engine technology is the reason for its high power density. they have a proprietary combustion cycle call HEHC (High. Efficiency. Hybrid. Cycle).
Air is compressed to a high compression ratio, fuel is then injected and compression ignited (CI-HEHC). The X Mini utilizes a spark-ignition (SI-HEHC) version of the cycle with a lower compression ratio standard for gasoline engines.

A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions.
Combustion is over-expanded using a larger expansion volume than compression volume, as in the Atkinson Cycle.

Cycle-skipping power modulation allows high efficiencies while cooling the engine’s walls and providing partial heat recovery. Water can be injected internally to cool the engine. Some of this cooling energy is recuperated, as the water turns to steam, increasing the chamber pressure.

LiquidPiston's Combustion Engine

Engine size comparison, LiquidPiston on the right, typical diesel on the left.

LiquidPistons advantages –

These engines have many advantages, from reduced weight to reduced Engine manufacturing costs. The efficiency of the vehicle Goes up directly resulting from engine efficiency and the weight savings. Plus with the ability to run different fuel sources the carbon footprint of these engines becomes negligible.

LiquidPiston's Combustion Engine

LiquidPiston’s 70cc 5hp engine.

LiquidPiston R&D – 

LiquidPiston is currently doing R&D on their mini-x engine, a version they claim will weigh 3 pounds and produce over 5 hp at 15,000 RPM. The size of this engine would work well in the handheld combustion segment. Another current engine model in R&D is LiquidPiston’s 40hp diesel engine. Weighing a fraction of its standard combustion counterpart.

LiquidPiston's Combustion Engine

70hp model.

conclusion – 

Time will tell whether or not LiquidPiston’s engine is capable of the service intervals required by the riggers of day-to-day use, With durability testing currently underway

We can see how this engine design would thrive between the frame rails of a modern motorcycle. Our industry thrives on both the pursuit of power and weight loss to which LiquidPiston offers both, Efficiency being the bonus.

As the CEO of The Hard Tail, Jacob Stoner leverages years of immersion in the world of motorcycling. He not only embodies the spirit of the open road as a devoted rider, but also has experience in custom motorcycle design. Though he has dipped his toes into the realm of customization, his main focus remains on riding and the motorcycle community at large. The Hard Tail, for him, is more than just a professional endeavor – it's a reflection of his enduring passion for motorcycling.


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