It’s Opposite Day For This Novel Wankel Engine

The Wankel engine seems to pop up in surprising places every so often, only to disappear into the ether before someone ultimately resurrects it for a new application and swears to get it right this time. Ultimately they come across the same problems that other Wankels suffered from, namely poor fuel efficiency and issues with reliability. They do have a surprising power-to-weight ratio and a low parts count, though, which is why people keep returning to this well, although this time it seems like most of the problems might have been solved simply by turning the entire design inside out.

A traditional Wankel engine has a triangular-shaped rotor that rotates around a central shaft inside an oval-shaped housing. This creates three chambers which continually revolve around inside the engine as the rotor spins. The seals that separate the chambers are notoriously difficult to lubricate and maintain. Instead of using a rotor inside of a chamber, this design called the X-Engine essentially uses a chamber inside of a rotor, meaning that the combustion chamber and the seals stay in fixed locations instead of spinning around. This allows for much better lubrication of the engine and also much higher efficiency. By flipping the design on its head it is able to maintain a low moving parts count, high compression ratio, and small power-to-weight ratio all while improving reliability and performance and adding the ability to directly inject fuel rather than rely on carburetion or other less-ideal methods of fuel delivery that other Wankels require.

Astute internal combustion aficionados will note that this engine is still of a two-stroke design, and thus not likely to fully eliminate the emissions problems with Wankels in a way that is satisfactory to regulators of passenger vehicles. Instead, the company is focusing on military, commercial, and aerospace applications where weight is a key driver of design. We’ve seen time and time again how the Wankel fails to live up to its promises though, and we hope that finally someone has cracked the code on one that solves its key issues.

28 thoughts on “It’s Opposite Day For This Novel Wankel Engine

  1. I was about to comment “Didn’t ‘Liquid Piston’ already do this years ago” then followed the link and realised that this _is_ Liquid Piston.

    It does seem like a clever design, like the best ever Betamax in a world of VHS (inexact analogy, as no-one was actively legislating against Betamax)

      1. Those rules aren’t for internal combustion engines. They’re for cars.

        Internal combustion engines aren’t just used in cars.

        From the article: “Its immediate use cases are expected to be in portable generators and UAVs, although a separate project is evaluating it for use in a hybrid-electric VTOL UAV.”

        These engines are pushing the power/volume and power/weight boundaries, and it’s safe to say pure electric isn’t going to touch that until they can grab and vent oxidizers from the atmosphere, too.

      2. I love the comment board on that site. It’s full of upper-middle-class twits who just don’t realize that the new rules make new cars completely unaffordable to 80% of the population.

        1. Don’t think unaffordable is part of the master ‘plan’? It will work in the long run….

          That’s why in my ‘circle’ we talk about keeping our current vehicles and eventually put permanent license plates on ’em. Last year I did that on my ’97 RAM. Keep it for rest of my life. Can’t really afford the new stuff they putting out with all the useless electronic do-dads (more to go wrong) they put in these vehicles when all you need a vehicle for is to get from location x to location y. The environmental movement now is now a ‘religion’ which is trying to force everyone into their way of thinking… Sad.

        2. Yep. And nothing makes a bureaucrat feel more proud than long lines at the E vehicle chargers. Hopefully the rules will get rolled back. They are idiotic and worthless.

  2. Orbital Engine company in West Australia did produce direct injection 2 stroke engines that did exceed emission requirements (at the time). The concept was used by Mercury Marine for some time, though eventually dropped for 4 stroke due to bad press on 2 strokes generally making it a tougher sell.

  3. These guys keep popping up. They claim the apex seals wont be a problem because they arent moving, but friction is friction, wear is wear. They *WILL* be a problem. However, their design allows for something other rotary designs do not – externally replaceable apex seals. It can be as easy as changing spark plugs…well, almost. Angles won’t be great, and the seals need to be spring loaded, but they could still be held against a threaded fastener, long enough to relieve spring pressure, and allow the apex seal to be replaced without cracking open the motor. Until they do this, its *just another rotary* with all the problems associated with rotary engines.

    1. No, the “moving” part is real because if the seal’s in the rotor, the forces between the seal and the sealing surface (the housing) vary as a function of load (due to the seal being located in the rotor and necessarily having play). Modern rotaries “fix” this by essentially oversealing, which means they wear more. If the seal’s stationary, you don’t need that.

      The other point is that if the seal is in the rotor, you can’t lubricate it directly because it’s moving. With the seals being stationary, you can lubricate them from the housing directly. Imagine like, a springed cylinder that ends up picking oil from behind it much like rings. In the assembly/disassembly videos you can see the shaft for the seal in the engine.

      You don’t have to have apex seals be easily replaceable, rings aren’t either.

  4. Wait.. it’s not a new battery (not yet out of the laboratory)… or a new EV (that is still in design)…or a new electric non rare earth element motor (theoretical) ? Seems we have been assaulted by tons of articles of the aforementioned lately (not HaD but all news media). Nice to see an article on a new (or improved) ICE concept that is more than smoke and mirrors (and not pandering to the green crowd). Liquid Piston seems to be headed in the right direction. Except for the emissions it would make a good match, size and performance-wise, in a hybrid.

    1. Yeah how are they supposed to vertically integrate this for maximum profits, from the rare metal mines in China and Africa all the way up to the captured regulation body which is led by a woman who shut down the largest US rare earth mine so that her husband’s shares in the Chinese one would explode? They make hundreds of millions on a combined salary under 400k, but I’m sure they do it because they love the environment

  5. Wankels are not two strokes as the exhaust and intake don’t happen at the same time. They are more akin to four strokes as they have an intake, compression, combustion, and exhaust cycle.

  6. That reversal of the NSU/Mazda Wankel was know when the Wankel engine was patented. (~1957). It definitely is nothing new. NSU had the DKM and the KKM. DKM= Drehkolbenmotor, it had the rotor and the housing rotating. The eccentricity was the distance between the centre of the housing and the centre of the rotor. KKM= Kreiskolbenmotor where the centre of the rotor orbits around the centre of the housing, while rotating around its own centre. The original DKM by Felix Wankel was converted by NSU to the KKM for practicality reasons by Hanns Dieter Paschke.

    The Mazda Wankel had high fuel consumption, mostly due to the large surface area of the combustion chamber, equivalent stroke-to-bore ratio is only near 0.33, lower than the former F1 engines of 0.40, and by higher seal leakage allowing only one apex seal. It’s like having one piston ring in the RPE. The same will apply to the LP inverse engine.

    The LP engine has a few good features: The spark plug does not have to be recessed into the housing and the combustion chamber is more favourable for fast combustion. The stationary apex seal are not exposed to centrifugal forces. The contact pressure is only that of the seal spring. Yes, lubrication is easier.

    Negative points are:The air inlet and outlet is through the central shaft, which was the main reason NSU did not do that version.

    Last point: The LP version is equivalent to an inline 3-cylinder, 4-stroke RPE. The RPE has good control of the intake and exhaust. LP does not. However, The RPE nas better seals. LP is smaller in size and also has 3 spark plugs. The claim of the HEHC seems wishful thinking. To combine only the good features of Diesel, Otto and Atkinson is unrealistic. Adding heat at constant volume (Otto) is not possible, 7000 rpm for a Diesel engine? LP has 2 shaft rotation for all three chambers to fire just like the 3-cylinder, 4-stroke RPE.

  7. Mazda RX8 ans citroen were the only cars buolded with rotative motor. And it was catastrphic for repairs…. But it is a technology whiche is to be learn to everybody who wants to know this….

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