Automotive

Game-changing rotary engine muscles a go-kart

Game-changing rotary engine mu...
This tiny engine, compared here to an iPhone, outputs almost 3.5 horsepower
This tiny engine, compared here to an iPhone, outputs almost 3.5 horsepower
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This tiny engine, compared here to an iPhone, outputs almost 3.5 horsepower
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This tiny engine, compared here to an iPhone, outputs almost 3.5 horsepower
Front and side view of the X Engine in its Mini form. This rotary engine is scalable to over 1,000 horsepower
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Front and side view of the X Engine in its Mini form. This rotary engine is scalable to over 1,000 horsepower
The engine's parts in their entirety, showcasing its simplicity – to the right are the central rotary parts, with the oval-shaped to rotor to the right of the shaft; the holes at bottom allow for air intake while the holes at top allow for exhaust expansion to eliminate the need for a muffler
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The engine's parts in their entirety, showcasing its simplicity – to the right are the central rotary parts, with the oval-shaped to rotor to the right of the shaft; the holes at bottom allow for air intake while the holes at top allow for exhaust expansion to eliminate the need for a muffler
The LiquidPiston X Mini (right) is roughly 30 percent smaller and lighter than the equivalent four-stroke piston engine it replaces
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The LiquidPiston X Mini (right) is roughly 30 percent smaller and lighter than the equivalent four-stroke piston engine it replaces

Imagine an engine that's 30 percent smaller than a traditional piston design of like output, and that runs smoothly, with less noise and vibration. Plus, it burns several types of fuel. That's the LiquidPiston X rotary engine, which was recently demonstrated powering a go-kart.

The LiquidPiston rotary engine is a non-Wankel design that we've featured on Gizmag before. Back in 2014, the company announced the engine's development. Now it's showing the new engine with a novel application to showcase its power-to-weight capabilities.

The LiquidPiston X Mini shown in the video at the bottom of the page has nearly 2 horsepower per pound (3.3 kW per kilogram). It's 30 percent smaller and lighter than the equivalent spark-ignited gasoline engine it replaces, and can be up to 75 percent smaller than a like-output diesel engine.

The LiquidPiston X Mini (right) is roughly 30 percent smaller and lighter than the equivalent four-stroke piston engine it replaces
The LiquidPiston X Mini (right) is roughly 30 percent smaller and lighter than the equivalent four-stroke piston engine it replaces

Even better, the engine's design means that it has no poppet valves and exhaust is balanced through over-expansion, removing the need for a muffler. The X rotary engine can be as much as 20 percent more fuel efficient than its gasoline counterpart and 50 percent more efficient than an equivalent diesel engine. What's more, the LiquidPiston X can be powered by gasoline, diesel, natural gas, or JP-8 fuel. The design, says the company, is scalable from 1 horsepower to over 1,000.

The X Engine is designed as a unique rotary that has three combustion events per rotor revolution, explaining its high power density and balanced operation. The engine is designed to be made with 2-dimensional manufacturing methods, making it simple to build. This also means that it can be easily modified by enthusiasts – something that LiquidPiston is expecting, having released a developer's kit for the X Mini.

The engine's parts in their entirety, showcasing its simplicity – to the right are the central rotary parts, with the oval-shaped to rotor to the right of the shaft; the holes at bottom allow for air intake while the holes at top allow for exhaust expansion to eliminate the need for a muffler
The engine's parts in their entirety, showcasing its simplicity – to the right are the central rotary parts, with the oval-shaped to rotor to the right of the shaft; the holes at bottom allow for air intake while the holes at top allow for exhaust expansion to eliminate the need for a muffler

One of the secrets in the X Engine's design is the unique rotary cycle. Unlike a Wankel rotary, which uses a triangular center rotor, the X Engine has an oval-shaped rotary which rotates in a cloverleaf-like core. This creates higher compression with better seals and exhaust pressure. It also creates a larger expansion volume than compression volume, similar to the high-efficiency Atkinson Cycle engine used in hybrid vehicles.

The design of the X Engine also allows for cycle skipping for lower-output needs and low-RPM power. In larger versions of the engine, LiquidPiston says, water can be injected into chambers after the exhaust cycle to cool the engine when under high loads.

The engine being used in the video to power the go-kart is a four-stroke 70cc gasoline version that produces about 3.5 horsepower (2.2 kW) at 10,000 rpm. LiquidPiston expects to have the engine producing 5 hp (3.7 kW) soon.

Source: LiquidPiston

LiquidPiston X Mini Go-kart

25 comments
Chizzy
awesome, turns any electric vehicle into any any fuel vehicle when added as a generator.
Milton
3HP @ 10,000 RPM ? holy-moley!
Mr T
Wow, I just don't get why people are still wasting so much time, money and resources on developing IC engines when electric motors are smaller, have higher torque and power outputs per volume/weight, are more reliable, last longer and are silent. Battery development is happening at such a rapid pace now that ICE vehicles are going to be considered dinosaurs within a decade or two (many people already consider them to be!)
SaysMe
The two of the first applicatios of this engine should be, generators and lawn equipment! Then move on to bigger versions...
Stradric
@MrT: Well, this is not being touted as a clean energy solution. It's more of an interesting engineering accomplishment. Academically interesting.
Tom Lee Mullins
I think that has a lot of potential. I think it could power a generator and be used as a range extender in electric or fuel cell vehicles. Since it can be small or really big, it could power vehicles of different sizes. Since it uses a variety of fuels, it could be very green.
Grunchy
More than merely academically interesting - Dev kit starts at $30,000! I think I just figured out what's wrong with this motor. If it has any utility - which btw has yet to be proven, and in particular emission sins - it will have to wait 20 years for the patent to expire. Oh well, see you later.
Mzungu_Mkubwa
Are you listening Mazda? (or any other automotive or aviation company willing to take a risk on awesome?) Let's get this sucker going, and pronto! ------------ @Mr T: These are still being developed simply because we're still going to be using I/C engines for some time to come despite such "rapid pace", and any improvements are welcome and useful, as long as there are those willing to take on the commercialization challenges. For all the battery development going on, there is still lacking a sufficient way to store enough electrical energy in a portable, cost-effective and safe fashion. Liquid carbon-based fuels still hold a huge advantage in this area. The nice thing about this design is its flexibility in the kinds of such fuels it can utilize, including, I'm sure, synthesized types. I say, "keep at it folks!" Let's keep 'em coming! ☺
Jimjam
It could be a big deal for hybrid flight using gasoline and this engine to generate current powering multiple electric motors. You could use batteries, but their power stored to weight ratio is still way to low to be applicable or more than short flights in the medium term.
WilliamEdstrom
@MrT ICEs will be with us for a long, long time. When electric finally does become truly mainstream (>40% of vehicles on the road) the price of fossil fuels will go down, limiting the capture of the remaining market. In the mean time more efficient engines are very important. That said, rotary engines are not more efficient. Have they addressed the lubrication or MPG problems with this design?