This inside-out design solves most of the rotary engine’s problems
- Thread starter JournalBot
- Start date
Aww man, it’s ok to call him out on it, but don’t drag Doritos down with him!
Upvote
31
(31
/
0)
Yeah I got myself an oil siphon and the top mounted filters on the TDI were great for easy changes. No need to get under the car.
Upvote
1
(2
/
-1)
Looking at the about us page, I do not think they can just do this themselves easily.
They have been working on it for a while, and can produce in some small volume, but that is not a huge manufacturing facility. They probably do not have that kind of expertise (or money).
The idea is a good one, and the cycle should be efficient in a few ways, but competing engines have seen a very large amount of refinement in general. It still will not be easy to bring this to market, especially for something with reliability requirements like a passenger vehicle.
Upvote
18
(18
/
0)
Its not that there are no seals. Its that the seals are now in the engine housing instead of in the rotor. Getting oil to the rotor (and out the seals mounted there) was very tricky. Getting oil to the seals in the engine housing will be easier and more-efficient.
HOWEVER, the seals will still be a wear item and there's no way to avoid some oil-burn due to the arrangement of seals swiping across the "piston" surface. Of course, typically reciprocating engines also have a little bit of oil burn (as the oil-control rings on the sides of the pistons allow a little bit of oil to leak by). The question is whether the seal wear and the oil-burn are both low-enough (and the new shape's compression-ratio & thermodynamic efficiency high-enough) to make it competitive with small reciprocating engines.
Upvote
33
(33
/
0)
While cool, it really messes up one of my favorite explainers for how rotary engines work. (I still would like to drive an RX-7 or RX-8 in anger someday.)
I had an RX-8. It was a blast and surprisingly capable. The weight balance was perfect and you could toss it around super easily. I miss it somewhat regularly. I don’t miss the maintenance and the terrible fuel economy.
Upvote
13
(14
/
-1)
Manufacturing themselves is just a different risk. Setting up large volume manufacturing is a huge capitol expense which would require them to raise a lot of funding. Then you are betting the entire company on getting the manufacturing plant up and going and being successful.
Upvote
15
(16
/
-1)
Wankel seals on apex of triangular rotor = high wear, poor lubrication. Cam rotors = good surface area, less wear, improved combustion.
Upvote
4
(6
/
-2)
Most modern submarines are moving to pumpjets. They're actually less efficient, but they significantly solve the cavitation issue.
Upvote
14
(14
/
0)
There is a huge space of possible engine designs that have not yet been explored. A great many more possible designs were explored in the early days of engine design, but either failed to catch on, or died out entirely. When was the last time you saw a Napier Deltic engine, or anything with sleeve valves?
I've been keeping an eye on a lot of these new engine startups for decades. They always burst onto the scene as a reveal of a skunk-works project by a handful of really bright engineers and technologists, who put together a beautifully machined prototype in their garage. There's a flurry of media attention about how THIS TIME, the cool new tech will really be revolutionary. They raise some capital.
Then they go quiet for a while. A long while.
Then they show up somewhere on page 30 of a newsletter about pink-sheet stocks.
The OX2 engine has been in development for what, a quarter-century now since they showed their 180 lb prototype beating the crap out of a standard small-block Chevy on the dyno? And AENG stock is now down to $33.... not per share, that's the market cap of the whole company?
Getting the incredibly cool new engine to work on the test bench is hard, but it's actually the easiest part of the whole process. Once you have it running, you need to keep it running without wear & tear for thousands of hours. Then you need to get it to meet emissions regulations. You need to figure out a manufacturing process that gets your BOM cost down to less than that of competing engines, which have 120 years of factory optimization behind them. Then you need to make prototypes and convince other companies to test them and invest in them. Then you need to build out a full supply chain and a spare parts distribution network, and train thousands of mechanics to work on them. All of that is hard, and expensive, and risky.
Boats would be a good market, especially if it's multi-fuel and can sustain continuous-duty operation. When the engine gets installed and rigged before the deck and superstructure are added, it's easy to forget about the importance of access....
PHEVs would also be an obvious choice. Along with portable generators. And sports cars. And UAVs. I like that they're considering mid-range power levels (10-100 hp) which is a regime where it's often hard to find good off-the-shelf choices in many applications.
There are plenty of markets willing to throw money at it. The hard & expensive part is the remaining development and commercialization to go from a lab prototype to mass production, and then building out a global parts and support network.
Last edited:
Upvote
36
(36
/
0)
I've seen this a year... or maybe more ago?
They certainly have some great ideas that should make the rotary better. But it looks like they're still in the "get funding" stage. Unfortunately with a lot of engine designs, you can only really tell if it's any good when the rubber hits the road, so to speak.
Run a dozen of them for 100,000km in real conditions and let's see what happens. Things that should have been solved can turn out to not be, and new issues will pop up. Nobody tries to make a bad engine but even major manufacturers screw up basic I4 deigns.
Nissan and Mazda themselves had some really cool ideas with variable compression ratios and and compression gas engines, they did make it into production and seem to actually work, but yet they haven't taken over. In reality the benefit might not be worht it. I do hope it works great, of coure. Just been burned before.
They certainly have some great ideas that should make the rotary better. But it looks like they're still in the "get funding" stage. Unfortunately with a lot of engine designs, you can only really tell if it's any good when the rubber hits the road, so to speak.
Run a dozen of them for 100,000km in real conditions and let's see what happens. Things that should have been solved can turn out to not be, and new issues will pop up. Nobody tries to make a bad engine but even major manufacturers screw up basic I4 deigns.
Nissan and Mazda themselves had some really cool ideas with variable compression ratios and and compression gas engines, they did make it into production and seem to actually work, but yet they haven't taken over. In reality the benefit might not be worht it. I do hope it works great, of coure. Just been burned before.
Upvote
-5
(5
/
-10)
Exactly what I was also curious about. Seems like you can have any number of chambers, why did they choose three?
Upvote
-2
(1
/
-3)
With two rotors, you just invert one. Have the intakes on the ends, and a common exhaust in the center. With more than two, you would need a significantly heavier side-ported shaft, and a plenum to feed it.
Upvote
12
(12
/
0)
Modern US Navy submarines do. Royal Navy submarines have been using them for, well, decades longer, and a lot of torpedoes used them long before that.
It's gratifying to see that USN boats are now effectively clones of the basic architecture that the RN had, all the way back in the 1970s. Though they still don't put beaches on the US boats, for some reason.
Upvote
5
(6
/
-1)
It sounds like they're trying to get around this by getting funding for manufacturing from DARPA, which gives them a relatively low-risk way to build a manufacturing base and not dilute their ownership by issuing stock. Not a bad start-up method (albeit slow), presuming your employees don't revolt over working for the military.
Upvote
15
(15
/
0)
That's where most radically new engines die. Getting it to work on the bench is hard and expensive. Getting it to work for 8,000 hours under real-world loads without self destruction is obscenely hard and absurdly expensive.
Novation Analytics figured that Nissan's VC-Turbo variable compression scheme was good for an 11% improvement in fuel economy in the QX50 versus a fixed-compression equivalent.
https://www.caranddriver.com/features/a24434937/nissan-new-vc-t-engine-fuel-economy/But it's still a CVT-equipped QX50; I don't think I've ever seen the word "unfortunately" used as liberally as it is in the reviews of that thing.
The engine is just one component of a car. Very few people buy cars based on the engine alone; they buy based on the entire package and experience.
Upvote
12
(12
/
0)
The RX-7 is a lot of fun to drive. Light, perfectly balanced, rear wheel drive. Unfortunately, it doesn't produce much horsepower unless it's in the top half of the tachometer. And even then, only maxes out at 180ish for a '87 turbo. Also, I found it's not very forgiving if you don't correct oversteer quickly (at least, that what my ham-handed driving skills found).While cool, it really messes up one of my favorite explainers for how rotary engines work. (I still would like to drive an RX-7 or RX-8 in anger someday.)
One nitpick about that diagram - the spark plugs don't have that little hook shaped electrode. (At least, my '87 doesn't). The electrodes are a pin in the middle and another that goes around it, so it can sit close to the face of the combustion chamber.
Upvote
5
(6
/
-1)
yeah, this thing has both apex seals and face seals, but since the apex seals don’t have to traverse the open port holes as in a traditional wankel, apex seals will wear less. The problem still remains with the face seals though. So, this engine is likely to be less reliable long term compared to a regular piston engine but probably quite a bit better than a traditional Wankel.
Upvote
3
(4
/
-1)
This X-engine is probably rpm limited, the article is silent. But the low hp test variants are telling. It is pollution constrained in the article. Small 8% efficiency is 0 benefit .v. BEV. It’s that 75% weight reduction that’s its real MVP, as you surmise.
DARPA is done with it. So it joins the lawnmowers and gensets.
Upvote
-4
(4
/
-8)
I also miss my RX-8, and largely for the same reasons.
I also don't miss constantly feeding it oil and only getting 16mpg no matter how I drove it lol.
Upvote
7
(8
/
-1)
Upvote
0
(0
/
0)
Upvote
6
(6
/
0)
Marine engineer here...These seem like a great idea for large ocean-going ships with slow-speed direct-drive engines (no gearbox.) Most other commercial vessels use variable-pitch/constant speed propellers, which to me look fundamentally incompatible with the toroidal design. These have two major advantages; they dramatically reduce the complexity of the gearbox and clutch (no need for a reversing gear), and they allow allow ships to make electricity from a simple PTO off the main reduction gear driving a generator. (W
Upvote
14
(14
/
0)
I expect putting the seals in the housing means you could make much taller seals, with a longer wear life before needing replacement.
Upvote
6
(6
/
0)
"That's a big reason why we are raising outside capital, to cross these productionization and emissions bridges so that we can get to the commercial market."
I'm curious about the emissions of this engine. That huge narrow area that opens up just after ignition is unlikely to burn completely. Otherwise, it's a pretty cool design.
I'm curious about the emissions of this engine. That huge narrow area that opens up just after ignition is unlikely to burn completely. Otherwise, it's a pretty cool design.
Upvote
8
(8
/
0)
In a Wankel the fuel-air mixure moves around.
Fuel-air enters the engine in one location where the intake ports are.
Then it moves and gets compressed into the area where the ignition plugs are;
Then it keeps moving and expanding and then compressed again towards the are where the exhaust ports are.
(Note the absence of valves.)
LiquidPiston's engine is somewhat closer to 3 cylinder radial engine.
There are 3 chambers and in each chamber the fuel-air goes through all 4 states. And each chamber has it's own set of
But instead of 3 pistons reciprocating they have one rotor rotating.
Last edited:
Upvote
14
(14
/
0)
It's all fun and games changing the oil filter on a Subaru, but god forbid you want to change a bog-standard headlight. At least on the Outback, you're fumbling around up to your shoulder through the unbolted plastic liner of the f'ing wheel well from underneath. To change a regular low-beam. WUfff.
Upvote
12
(12
/
0)
So it turns out that the secret to converting the Cooley rotary steam engine to a successful internal combustion engine is to keep the "cylinder" stationary and only have the "piston" rotate?
I wonder how Mr Umpleby (1908) and Mr Tsukagawa (1966) would feel about the news...
(not trying to detract from LiquidPiston's success; just thought I'd share a bit of the history of that specific "cylinder" and "piston" combination)
I wonder how Mr Umpleby (1908) and Mr Tsukagawa (1966) would feel about the news...
(not trying to detract from LiquidPiston's success; just thought I'd share a bit of the history of that specific "cylinder" and "piston" combination)
Upvote
14
(14
/
0)
I think I've been seeing news about them for a decade+. For along time they seemed sketchy with the constant "invest in us" ads/articles, it seemed like a bad Kickstarter.
However they finally closed their investment window and actually have a contract to develop a finished product.
Hopefully they succeed - especially since they're a relatively local company to me.
But I expect once they see more substantial success that they'll be bought by a larger company that will either at best slow the advancements/rollout of the tech or at worst hoard the patents and do nothing with them once existing contracts are fulfilled.
However they finally closed their investment window and actually have a contract to develop a finished product.
Hopefully they succeed - especially since they're a relatively local company to me.
But I expect once they see more substantial success that they'll be bought by a larger company that will either at best slow the advancements/rollout of the tech or at worst hoard the patents and do nothing with them once existing contracts are fulfilled.
Upvote
8
(9
/
-1)
Upvote
16
(17
/
-1)
Way too many modern cars need you to remove the whole bumper to change a light.
Upvote
6
(6
/
0)
From the caption of the top picture:
Elsewhere, there's an i between the u and the d.
How sure are you he wasn't saying "sealing" surface?
Upvote
8
(9
/
-1)
Toroidal propellers are beautiful, aesthetically pleasing pieces of engineering, that are even more satisfying on a fuel cost analysis spreadsheet than they are to the machinist's eye.
Having cleared my fair share of weeds and crap from the blades of traditional propellers, I would hate to be the poor SOB who draws the short straw when it's time to get a 14" diameter log, or a tangled fishing net, or a dolphin carcass, out from between the blades of a toroidal prop.
Upvote
17
(17
/
0)
My 1988 RX-7 also got 16 mpg. Loved the car otherwise though.
Also got a speeding ticket for the record books with that car. Bought a boring car after that.
Upvote
2
(3
/
-1)
I wonder what this thing’s power curve looks like. Could be that its efficiency partly comes at the expense of the kind of power curve you need for a wheeled vehicle. Airplanes do much better on narrow power curves, as their loads don’t change so much. Generators need to be able to change loads, though, so maybe this does have a good power curve.
Upvote
3
(3
/
0)
"We can directly interface the apex seals with the face seals. Now that there are no gaps anymore, the blow-by is significantly reduced, and... we can directly lubricate the seals by metering tiny amounts of oil... right to the ceiling surface,"
I'm still not understanding how the seals are changing. And I think the last "ceiling" might be "sealing". Doesn't help I don't know where the face vs. apex seals are either (to visualize how they're changing and magically have no gaps now).
But by the helpful video link added at the end, it looks like there is still a sealing point for each cylinder's combustion area (apex seal before, right?). And there is a surface that needs to brush along it through the cycle... which I assume would have similar results as the wankel (oil being moved past the interface, and burning).
Either way, color me curious. I just hope this doesn't get stuck somewhere, behind a paywall. Only appearing in the military stuff for a few decades, with no car company willing to pay royalties to use it.
I'm still not understanding how the seals are changing. And I think the last "ceiling" might be "sealing". Doesn't help I don't know where the face vs. apex seals are either (to visualize how they're changing and magically have no gaps now).
But by the helpful video link added at the end, it looks like there is still a sealing point for each cylinder's combustion area (apex seal before, right?). And there is a surface that needs to brush along it through the cycle... which I assume would have similar results as the wankel (oil being moved past the interface, and burning).
Either way, color me curious. I just hope this doesn't get stuck somewhere, behind a paywall. Only appearing in the military stuff for a few decades, with no car company willing to pay royalties to use it.
Upvote
0
(1
/
-1)
I got popped in the RX-8 on the expressway one time doing triple digits (I was admittedly being dumb but there were no other commuters around at the time). I was sure I was going to jail that afternoon but I got off with a failure to obey a traffic control device and a stern lecture. To this day I'm not sure why he let me go.
I got rid of the RX-8 because I knew the engine was a ticking time bomb that I didn't want to deal with and I was tired of the wife complaining that she couldn't drive my cars because she doesn't drive manual. Bough an Acura and hated driving automatic so much I got rid of it a year later and bought a manual Z, so I'm back to the horrendous gas mileage but at least I don't have to worry about apex seals lol.
Upvote
4
(4
/
0)
This is HEHCin’ cool.
More seriously, it really is awesome to have a geometry that allows them to pick apart thermo cycles, as the article says. The cutaway video somebody posted really drives home how they can do that. The most bizarre bit for me is the intake through the inside of the moving rotor.
Also, Mazda sports car plz…
More seriously, it really is awesome to have a geometry that allows them to pick apart thermo cycles, as the article says. The cutaway video somebody posted really drives home how they can do that. The most bizarre bit for me is the intake through the inside of the moving rotor.
Also, Mazda sports car plz…
Upvote
1
(1
/
0)