Internal combustion engines can have their revolution too: meet LiquidPiston and HEHC

The recent Nissan announcement of a revolutionary fuel cell, the SOFC, may have given internal combustion engine lovers the impression their beloved way of life is doomed or condemned to a restricted circle of petrolheads. But LiquidPiston wants to give them a sparkle of hope with their invention, the HEHC, or High Efficiency Hybrid Cycle. This new engine design mixes concepts such as the rotary engine, also known as Wankel, after its inventor, with air cooling, a fixed volume combustion chamber that ends up being 3 of them and a piston that looks like a peanut. Check this beauty working below to better understand the concept.

Instead of a triangular rotor moving inside a peanut-shaped space, Nikolay and Alec Shkolnik, inventors of the HEHC, have inverted the concept. The engine has the peanut-shaped piston we have mentioned before moving inside a triangular space. Each of the vertices become a combustion chamber, while only one side of the common Wankel engine has a compression function. See a conventional rotary engine in the video below to compare.

Ultra high energy efficiency

Even being an Atkinson cycle 4-stroke engine, with admission, compression, combustion and expansion, the HEHC engine is said to have an energy efficiency of 75%, or 50% more than the most efficient diesel engine. The first video shows that all the piston’s movements create at the same time an expansion and a compression movement, what helps explain its efficiency. There is no information on emissions, especially being such a simple engine, with no need of liquid cooling. We will contact the company in order to have more information about it.

So far, the engine has just been outside the lab to power a go-kart, as you can see in the video above. With 3 spark plugs, but it could also be powered by diesel or any other sort of fuel, according to LiquidPiston. The HEHC engine can provide 0.75 kW per 0.45 kg, or 1.7 kW per kg, a remarkable achievement. LiquidPiston has named the engine X-Mini. With only 70 cm³, it generates 2.6 kW at 10,000 rpm and weighs 1.8 kg. The company expects it to produce 3.7 kW at 15,000 rpm and to weigh 1.4 kg with further development. Listen to how it sounds in the video below.

LiquidPiston believes the HEHC can be used for applications of up to 75 kW with little change, but the concept can also be applied to production cars. In a 2012 press release, the company has invited automakers to know the concept in order. Will we ever have a HEHC car? Early to say, but we would really like to see it on the streets. Especially because we do not like to know that only about US$ 20 of each US$ 100 we spend on refueling a petrol car really converts into movement.

Gustavo Henrique Ruffo

I have been an automotive journalist since 1998 and have worked for many important Brazilian newspapers and magazines, such as the local edition of Car and Driver and Quatro Rodas, Brazilian's biggest car magazine. I have also worked for foreign websites, such as World Car Fans and won a few journalism prizes, among them three SAE Journalism Awards and the 2017 IAM RoadSmart Safety Award. I am the author of "The Traffic Cholesterol", a book about bad drivers that you can buy at Hotmart, Google Play, Amazon and Kobo.