Here’s a 4-pound, 3-hp experimental rotary engine in a go-kart

LiquidPiston’s X Mini engine

isn’t new

, but it is endlessly fascinating. It’s a rotary, but it doesn’t have much in common with the best-known rotary, the Wankel engine popularized by

Mazda

. The LiquidPiston engine uses an oval rotor that spins eccentrically in a triangular housing. A Wankel, by contrast, uses a triangular rotor spinning in an oval housing.

To show off the engine again (and keep interest on simmer), LiquidPiston shoved one into a go-kart to help demonstrate the power density. It’s rated at three horsepower at 10,000 rpm and weighs just four pounds, which is significantly lighter than the 40-pound horizontal reciprocating piston engine it’s replacing in the go-kart.

It’d just be nice, and more impressive, if LiquidPiston was comfortable showing the kart moving at something more than just off-idle speed. The video simply doesn’t demonstrate much except that the engine runs, at what seems to be steady throttle inputs.

The DARPA-funded company is hoping the tiny, light engine can be used in range-extender applications, as well as household power tools like lawnmowers and so forth. The range extender idea also parallels Mazda’s thinking with the

circa-2014 Mazda2 RE Range Extender

, which featured a 330-cc single-rotor Wankel that was only used to recharge batteries for the

EV

. It’s too early to tell if LiquidPiston’s engine will live up to its promise, and while this video does show it powering a vehicle it’s not a terribly impressive demonstration. If the company can overcome some of the inherent weaknesses of the Wankel and produce reliable, power-dense engines at extremely low weight in range-extender applications, it would be very impressive. We’ll keep following LiquidPiston and let you know how the X Mini develops.

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