“Inside-out Wankel” rotary engine delivers 5X the power of a diesel

https://newatlas.com/automotive/inside-out-wankel/

by geox • 3 years ago

255 200 3 years ago

debacle• 3 years ago

My understanding is that everyone acknowledges that rotary engines are great, bt in comparison to piston based engines they have far shorter longevity.

tudorw• 3 years ago

I understand this too, however, the technology might be worth revisiting with modern techniques, I understand the power output is 'smoother', which can reduce vibration, some applications might need that?

brodouevencode• 3 years ago

Nearly all engines need some level of vibration reduction if anything just to prevent it from damaging itself.

djaychela2• 3 years ago

They also have issues meeting emissions targets - both because of the basic design (there isn't the ability to actively control valve timing events), and also because they typically need some sort of lubrication for the combustion chamber. They are similar to two-stroke engines in these respects.

skullone2• 3 years ago

Running them at a pre-determined RPM constantly can resolve lack of VVT, but that limits their applications. New materials for apex seals being researched could alleviate their longevity issues too. But, I have a big soft spot for rotaries and would love to see them applied more :(

manarth• 3 years ago

Whilst also being worse-performing?

Take a two-stroke Moster 185 engine: 25 HP at 7.800 RPM, for a 15kg package.

I'd be keen to understand how (if) this outperforms a typical two-stroke.

Supermancho3• 3 years ago

My near-mint condition 2009 Mazda RX-8 never had a Wankel engine problem (over 100k miles). It would have easily lasted another 5 years without a doubt or hiccup.

Wankels are usually excluded from all engine comparisons, because it's a considered a different class...for piston engine marketing reasons.

I sold off my RX8 in 2018 because my fiancee and I moved to Seattle (passing emissions testing wasn't anything special). We needed the money and we had her car, which was more functional. I do miss it.

mywittyname2• 3 years ago

More antic-data: i worked with a guy whose brand new RX-8 needed two engines in the time we worked together. Granted, his was a 04 automatic, which is the worst combo. But still, Mazda didn't go out of their way to extend the engine warranties on the early RX-8s for no reason.

Did you happen to have an 08+ model with the updated engine and/or remove teh catalytic converter?

msandford• 3 years ago

The folks in the article seem to have figured some of the longevity problems out.

Gordonjcp2• 3 years ago

They're not great, at all. They have very few moving parts and they are very smooth because there are no reciprocating parts.

Other than that, they have emissions like 2-stroke engines because of the incomplete combustion and we have never been able to devise any kind of material to make the apex and side seals last anything like as long as piston rings.

Piston engines are a terrible way to power vehicles, but everything else we've tried is worse.

himinlomax• 3 years ago

Wankel engines are great in one respect, power density. But they have terrible reliability and fuel efficiency.

Turbine engines also have great power density and terrible fuel efficiency, but they are very reliable.

Diesel engines are reliable and fuel efficient but heavy.

This one appears to have improved reliability and fuel efficiency over the Wankel without sacrificing power density.

projct• 3 years ago

LiquidPiston addressed both of those issues.

busterarm• 3 years ago

My '88 RX-7's engine went 120k miles before I decided to rebuild it and it still probably had a good 30k miles before it would have 'gone'.

This is completely normal through the 70s and 80s when these engines were popular. We didn't start getting million-miler cars until the Lexus LS400 came out.

The problem with the rotary is heat and the damage it does to other components. The RX-8's engine design was actually bad and doesn't adequately lubricate, but that gets 'fixed' in the last three model years.

The biggest reason that RX-7 owners have seal failures are often due to adding on too much power without adequately upgrading the fuel system. Keep in mind that Wankel engines are absurdly popular in the world of amateur aviation without any of the stigma.

rascul• 3 years ago

Some years past, a friend who worked for Mazda explained to me that the engines need to be driven for a bit because until they're warmed up fully there can be a lot of carbon buildup and it needs to be run some amount of time to get the carbon through. Once they're warmed up and running for a bit they're fine. Supposedly it's the short trips of only a few miles that can kill them over time.

Not sure if that's correct.

Enginerrrd• 3 years ago

Yeah I talked to some race mechanics that said the mazda rotary engines had much better longevity if you really drove the piss out of them. They liked to rev high and hard, which would be basically consistent with that notion.

devnullbrain• 3 years ago

If we lived in a world of rotaries and BMW came out with the S85 we'd say that piston engines were emotive and fun but too unreliable for mainstream use. When we refer to rotary engines we mostly talk about two generations of one engine from one manufacturer used in sports cars that were designed before emissions targets changed.

ww5202• 3 years ago

The problem with rotary engine is that its max power efficiency is at a very narrow rpm range and loses power at most other rpm ranges. This is due to the constant air intake inherent in the design. Piston engine has variable valve air intake to ensure optimal air oil mixture compression to deliver max power efficiency at a long range of rpm’s. That’s why rotary design is not popular for cars.

Mazda is reviving small single cylinder rotary engine design for HEV by running it at a constant speed with max power efficiency to charge the battery.

mywittyname2• 3 years ago

A non-turbo diesel is an interesting choice of competitor. The big selling point of the Kohler motor is that it's almost silent - even the valve train is belt-driven to reduce noise.

Not sure a rotary engine screaming at 6500RPM is comparable here to a diesel with a peak torque at 2000 and peak power at 3600.

LiquidPiston has been working on these X-engines for nearly 20 years now,

I'm guessing they will never actually release a commercially viable product. 20 years to design an ICE is...too much.

Zak• 3 years ago

The specific version described in the article appears to be a Diesel rotary that runs on jet fuel with military UAVs as a primary application.

Cthulhu_2• 3 years ago

I think a lot of commenters in articles like this will only think about automotive as a use case for alternative engine designs.

I'm reminded of a linear piston engine (iirc two pistons that just go back and forth without their motion being translated into rotation; one where they were side-by-side moving alternately, the other one where they'd actually move towards each other and share a combustion chamber). The use case for that was to have the pistons move through coils, thus generating electricity. We used to have a flashlight that works with the same principle, shake it to generate electricity.

astral303• 3 years ago

rotary engines do not really scream at peak power... this is why Mazda has plans to use rotary at peak power to generate electricity for their hybrid EVs.

re 20 years to make a new engine point, compare investment $ in traditional ICE across the car industry vs investment $ into rotary or other alternative engines (the former is order of magnitudes more)

red-iron-pine• 3 years ago

Mazda still holding on to those rotary engines, eh?

Still, call my interest piqued. I'll keep an eye out for their Wankel-EVs

rgmerk• 3 years ago

As cool as the rotary engine is, Mazda’s attempt at a rotary hybrid is flogging the deadest of dead horses.

hommelix• 3 years ago

Yes this ils comparing apple and banana. 2-stroke vs 4-stroke, supercharged vs naturally aspired.

stronglikedan• 3 years ago

If it's truly a 5x size reduction, then there's still plenty of room for sound dampening materials!

toss1• 3 years ago

Seems likely. Several years ago when working on a hybrid-powered UAV, I was checking out high power/weight engine platforms, and actual Wankels in development or available did better.

A 30sec DDG search turned up options that are definitely better, e.g., the AIE 80S, with 15BHP/11.2kW at 5kg or their 225CS, with 40BHP/30kW at 10kg [0]. In contrast, this weighs 19kg to produce 26HP/20kW. The net power - weight for these Wankels is 2.24kW/kg and 3.0 kW/kg vs Liquid Piston's 1.05kW/kg.

While IDK about availability from AIE (it just turned up at the top of the search), I know there are others on the market that are/were available. Meanwhile the LP prototype still isn't available 7+ years after I was first looking at them, and the were suppose to ship "real soon now".

We'll see...

[0] https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/

m4633• 3 years ago

btw: I had a mazda rotary engine car, and the 7000rpm shown on the tach seemed exciting compared to a piston engine... except it wasn't really true. It really ran at 1/3 that speed.

pengaru3• 3 years ago

There's only a grain of truth to what you're saying here.

The eccentric shaft does indeed spin at the indicated RPM, just as a crankshaft on a piston motor does.

It's just the rotors move at 1/3rd the eccentric shaft's rate, which is a design feature enabling substantially higher than 7000RPM with little effort.

BWStearns2• 3 years ago

Sounds like it could be awesome for some GA applications given the lack of weight budget and it seems like they did solve the issues with rotaries. Hopefully someone starts cramming them in some experimentals!

stametseater2• 3 years ago

General aviation are perhaps the most cautious and wary ICE users around. Most of the engines used in GA, Lycomings and Continentals, are essentially 1960s designs with very well known cost, performance and reliability characteristics.

That is not to say change is impossible, GA's overdue changeover to unleaded gasoline seems like an inevitability. Unleaded gas is already being approved for many of these engines, like new production O-360 engines (which date back to the 1950s.)

BWStearns2• 3 years ago

General aviation are perhaps the most cautious and wary ICE users around.

That depends on if you're describing the pilots or the ~manufacturers~ Textron. The experimental fleet has been pretty adventurous and it's a fast growing fleet. I think most of the conservatism in GA ICE tech has been driven by the broader issue of consolidation into a near monopoly on the cheaper end of the market. If you have no competition then why bother innovating?

causi3• 3 years ago

Ok, so they're "shooting for" a performance of 1hp per 1.57 lbs of engine weight. A Toyota Camry engine produces 1hp for every 1.41 lbs of engine weight. It produces 1ft-lb of torque for every 1.94 pounds of engine weight, compared to 1.58 for the Camry.

How is this revolutionary motor being outdone by a mid-range sedan engine?

SV_BubbleTime• 3 years ago

Add 10,000 or 20,000 lbs to the vehicle weight, does it all scale the same?

causi3• 3 years ago

I'm not sure what your point is. The XTS-210 hasn't been put in a vehicle as far as I know.

shadycuz• 3 years ago

The engine is the size of a push mower.

XTS-210 is about the size of a basketball, weighs in at 19 kg (42 lb), and displaces 210 cc.

So you are talking about a 26HP lawn mower.

While the Camry might make more power at its normal size. It would not if you scaled it down to the size of a basketball. I'm guessing it would make 1-3HP at that size.

93po4• 3 years ago

A Traxxas 5407 TRX 3.3 engine used in RC cars makes 1.42 horsepower, weighs 305 grams, and fits in the palm of your hand.

This is 1hp per 0.46 pounds of engine weight, nearly three times better than the camry engine.

Granted an RC engine runs on a mixture of fuel and nitromethane, and doesn't have any reasonable durability compare to a Camry engine. But it also only costs $200.

ww5202• 3 years ago

The Camry engine has 4-6 cylinders for its size. A single cylinder is not much bigger than a basket ball.

bluGill5• 3 years ago

Every motorcycle mechanic I've seen has a sign in the shop: speed costs money, how fast do you want to go. That sign isn't referring to the costs to modify an engine to go faster so much as the cost to constantly rebuild the engine after they modify it to go fast. I've seen two identical engines, one rebuilt to stock and one rebuilt to max speed - the cost for both rebuild jobs was about the same (the parts for speed were more - but not much more compared to the labor which was the same), but the engine rebuilt to stock ran for thousands more hours, while the one rebuilt for speed has the mechanic bragging that it lasted a whole 80 hours!

Syonyk4• 3 years ago

How is this revolutionary motor being outdone by a mid-range sedan engine?

Go ask your Camry engine to make 100% rated power indefinitely, and see how long it holds up. That's the difference.

A typical car engine is designed to make 30-50hp sustained, and occasionally generate more power for reasonably short periods of time.

An aviation engine, generator engine, or any sort of "industrial" engine is going to be able to sit there, making full rated horsepower, for thousands of hours without any trouble at all.

causi3• 3 years ago

going to be able to sit there, making full rated horsepower, for thousands of hours without any trouble at all.

The XTS-210 can do that?

kube-system3• 3 years ago

IIRC some automakers do test automotive engines at 100% duty cycle (in a test stand configuration). And more than a few automotive engines are used in slightly modified variants for marine and aviation applications.

As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration.

Examples:

https://youtu.be/GNPB3RtHN2M

https://www.vikingaircraftengines.com/engine-options

bell-cot• 3 years ago

Their target market is the military - which has plenty of kerosene / jet / diesel fuels as part of its standard supply chain. The Camry engine will only run on gasoline - which the military neither carries, nor wants to.

bluGill5• 3 years ago

Toyota makes some great diesel engines (they don't put them to the US bound products in general), which could run on jet fuel with some small modifications.

codeflo3• 3 years ago

I know this is off-topic, but I'm curious. I always had the impression that even in the US, standard units are used for engineering. Reading about "ft-lb" makes me think I was wrong (and my head hurt, tbh). Do you really compute stuff like torque in imperial units? Don't you need weird factors in every formula to make that work?

bluGill5• 3 years ago

There are lots of weird factors in engineering anyway. We have different factors, but there are still factors. Besides, nobody is calculating this, they are measuring and that is just a matter of what label you put on the dial.

Most engineering in the US is done in metric units. Then marketing applies a metric to imperial conversion.

I suspect China does more engineering in imperial than the US, both in total an per capita: most things I buy made in America are all metric (cars are all metric except for parts designed in the 1960s and the adapter bracket to make them fit on a modern metric car). Most things I buy made in China are imperial. I don't really know for sure, but that is my impression of industry.

m4633• 3 years ago

For the camry, is that just the motor? Does it require support, like say the cooling system?

pkphilip• 3 years ago

I think the primary advantage is the size (about the size of a basketball) and the number of moving parts (just 2), and also its ability to use a range of fuels.

jldugger2• 3 years ago

I guess the "inside out" is that the rotary block is also the fuel injector? Would have to read more to figure out how they get fuel into a thing moving at thousands of rpm.

Etheryte• 3 years ago

We do this all the time with cylinders, no? I don't see how this is any different.

bagels3• 3 years ago

They were, I think, imagining placing the fuel injector on the moving part itself (eg the piston) which doesn't makes much sense to do, taking the inside out bit to the extreme.

bagels3• 3 years ago

That is unlikely, it's probably in the housing, just like a wankel.

HWR_14• 3 years ago

A traditional Wankel engine has a rotary block in the shape of a reuleaux triangle moving in a more cylindrical stationary chamber. The "inside out" refers to how this engine is a more cylindrical rotary block moving inside a stationary reuleaux triangle chamber.

andy_ppp• 3 years ago

I'm surprised the air intake isn't more aerodynamic, more like a fan blade to compress the air into the engine?

Could this engine be fitted inside the rear wheel to save space and weight as well?

bmelton4• 3 years ago

That's a really good idea.

Mazda is doing something that I think is fairly novel, which is almost exactly what you've described. They've scaled down the rotary engine from their RX cars to a single-rotor and put it into their new EV (almost tucked into the front wheel well,) and letting it act as a 70ish horsepower generator for the otherwise battery-powered car to extend range.

tromp• 3 years ago

Presumably this new model: https://www.greencarreports.com/news/1138444_mazda-mx-30-r-e...

digdugdirk3• 3 years ago

Mazda really seems like the only company innovating in the ICE space (this, wankel rotary engines, skyactive engines) and their cars look damn good these days too.

On top of that, they make fun cars. With buttons and knobs on the dash!

I'm glad they're still around doing their thing.

detourdog• 3 years ago

This was done by BMW for the i3 with REX (range extender) equipped models. To be classified as an EV the gas tank range can’t be greater than battery range. This led to a 2ish gallon tank.

jdmichal• 3 years ago

I always wondered why "electric with an onboard generator" didn't take off as a subset of available vehicles. AFAIK, hybrids all work with complex gear boxes to allow the engine to directly power the wheels, while also charging the batteries.

I suspect the answer is because it's more efficient from a MPG perspective to allow the engine to directly power the wheels, at the cost of the extra complexity of gearing. Converting motion to electricity back to motion is lossy, and even more so if you insert battery storage as an additional step.

hoosieree• 3 years ago

Actually mounting an engine inside a wheel increases "unsprung weight" which is bad for handling. But putting such small engines near the wheels (but still on the body so the suspension can do its job) that could indeed improve cargo space. Pushing the engine weight outward toward the wheels would also make the vehicle harder to rotate, which is bad for track cars and go carts, but good for passenger and freight vehicles.

AnotherGoodName• 3 years ago

You want the unsprung mass to be as low as possible. As in you want the wheels to be much lighter than the rest of the car for a smooth ride. The wheels should bounce around but the rest shouldn't. Newtons law and all.

Putting engines in wheels causes a very rough ride. Even if the engine is light you're still likely creating an order of magnitude more unsprung mass. That's an order of magnitude rougher ride.

Cockbrand2• 3 years ago

Surely the engineers who came up with this are a lot smarter than myself, but to me it looks like the lower half of the rotor rotates into the combustion and thus has to work _against_ its force. If this is true, I'd assume that this takes away a lot of effectiveness.

KAMSPioneer• 3 years ago

I'm not sure what you mean -- are you referring to at the end of the combustion cycle during the exhaust phase? If so, then because the exhaust channel is open, the gases in the combustion chamber won't be exerting appreciable force on the shaft/rotor, the gasses will simply escape through the exhaust channel. At least, that's how I see it.

But maybe I've understood you wrong.

Cockbrand2• 3 years ago

Yes, it’s a bit hard to explain, and I’m not a native speaker. But you got me right, and now I see that too. Thanks for the heads up!

qbrass• 3 years ago

It actually happens less on this engine than piston engines because the lobe on the rotor kind of rotates over the combustion chamber for a while instead of moving towards or away from it.

On the other hand, it exposes a lot of surface area to heat, which gets absorbed by the rotor but isn't used to turn the engine. It's a problem it shares with wankel engines. The advantage over wankels is the extra time air and fuel spends burning in the combustion chamber before the chamber volume expands. It means it gets more time to combust evenly which should help reduce both hydrocarbon and nitrogen oxide emissions.

eYrKEC2• 3 years ago

I know this goes towards steam-engine design, but why can't that heat be re-captured as steam? When the engine heat gets above a threshold, inject [distilled?] water instead of fuel.

spydum• 3 years ago

I suspect a lot of folks confusion on how this works is better explained by this from warped perception (first place I heard of this inverted rotary):

https://m.youtube.com/watch?v=jLtyNtf9_ew&t=10s

dingaling• 3 years ago

Confusion is also possibly due to misuse of the term 'rotary'. A true rotary engine turns on its crankshaft. The Wankel is a rotating-sleeve-valve engine.

LesZedCB2• 3 years ago

https://en.wikipedia.org/wiki/Wankel_engine

https://www.britannica.com/technology/Wankel-engine

both seem to disagree with your technical definition. at the very least, the colloquial usage is broad enough that adhering to some archaic technical definition isn't sufficient to explain some confusion.

even this wiki article says it's obsolete https://en.wikipedia.org/wiki/Rotary_engine

tbruckner• 3 years ago

Surprised they didn't consider the Middle-out wankel.

stillworks• 3 years ago

Haven’t been exposed to the rigorous competition of TechCrunch Disrupt as yet I guess ?

davidbanham4• 3 years ago

A commodity chainsaw (Stihl ms660) returns 1.4kg per kw from 2 stroke fuel. Before any performance tuning takes place.

That’s at about a quarter of the size of this. I bet there’s efficiencies to be had if it were scaled up.

I’m just not sure this is the game changing breakthrough the article’s tone suggests.

kortex2• 3 years ago

Two-strokes are extremely dirty, due to blow-through of the fuel-oil mixture, incomplete/less efficient combustion due to crude fuel metering, and inability to use conventional catalytic converters (due to fouling from the above two points). But they do afford roughly double the power-per-RPM of four-stroke engines, and a further power-to-weight multiplier due to their simpler design.

AFAIK there's nothing mechanically stopping you from scaling a 2-stroke, but it would very quickly render the immediate area noxious.

But they are simple, lightweight, and easy to shrink.

This is actually a really important point as we are trying to clamp down on VOC/NOx emissions. Ignoring CO2, two-strokes emit way more emissions than cars per unit work. But a 4-stroke engine, in addition to expense, does not lend itself to tools like chainsaws. In theory this engine could fill that niche.

davidbanham4• 3 years ago

The rotary in the article is a 2 stroke design, by my understanding.

Fuel injected 2 strokes have been around for years now. In saws, the Stihl 500i.

Scaled 2 stroke engines, both with and without fuel injection, have also been around some time. The KTM 300 XC is a very modern example with 300cc displacement, so the same general category as the one in the article. Modern outboards on boats go even bigger.

Yes there’s a push on at the moment to retire the fleet of small 2 stroke engines in older garden power tools. Emissions controls have been tightening up on new tools over the years. Electric tools are rapidly displacing them with lower maintenance requirements and less noise.

There’s a lot more to 2 stroke engine development than just saws and lawnmowers from the 80s, though.

Synaesthesia• 3 years ago

This mechanism is really ingenious. I really liked the video explanation, it does seem like a very efficient and promising design.

soliton4• 3 years ago

about 5 decades to late, but non the less impressive

elihu• 3 years ago

Kind of weird article that doesn't talk about either the main benefits or design hurdles. The advantage of the LiquidPiston design is that at the time of ignition, the combustion chamber is a roughly round shape, as opposed to a traditional rotary where it's a long crescent. This should theoretically improve the emissions and fuel economy to be more like piston engines.

I don't think Liquid Piston was talking about a 2-stroke version before. That's news to me, and it seems like it would throw out the efficiency/emissions benefits in exchange for more power. Maybe the author of the article was confused and this isn't actually a 2-stroke design?

The main design hurdle has been longevity. Their prototypes in the past only work for a short time and wear out. That's probably just a matter of doing the necessary R&D to figure out the best alloys to make the engine out, and the best ways to lubricate everything. It's not clear from the article if this new version has this solved so it can last a normal amount of time or not.

m30472• 3 years ago

2 stroke has poor unburned emissions because of mix flow-through when ports are open. If air charge / purge is completed before fuel is injected then that doesn't occur; whether that's diesel or something else is irrelevant.

As a bonus, built in EGR if properly managed.

abfan11272• 3 years ago

I thought 2-strokes had poor emissions was the injection of lubrication oil into the air fuel mixture. traditional 2-strokes I'm familiar with pull in air into the crank case (which requires lubrication), then uses a portion of the exhaust stroke to compress the fuel/air creating forced induction. By keeping air out of the crank case and providing lubrication delivery outside of the air/fuel mixture, emissions can be significantly improved. The article claims the design allows external lubrication, but it doesn't say how. I'd like to see how the seals are better than apex seals.

dsr_• 3 years ago

The four strokes of a four stroke cylinder are intake, compression, combustion, and exhaust. That's down, up, down, up. Since there's no down or up in any of this engine's combustion chambers, "strokes" is probably inappropriate.

Cthulhu_2• 3 years ago

I think for comparison, this (and the Wankel) would have to do two rotations for a single cycle.

RickHull• 3 years ago

The strokes have nothing to do with up and down (e.g. flat motors, like a boxer), but to do with compression and expansion. The direction of compression doesn't really matter aside from packaging concerns.

As you said, 4 stroke has intake, compression, combustion, and exhaust. That's expansion, compression, expansion, compression. It fires between compression and combustion.

A 2 stroke motor has compression and expansion. It fires between compression and expansion. Intake, exhaust, and combustion happen during the expansion phase.

A rotary motor is traditionally 4 stroke, and I'm not sure a 2 stroke version is feasible. The LiquidPiston rotary appears to be a 4 stroke to me, despite the article text.

ajmurmann• 3 years ago

All the numbers in the article were really small and seemed to aim at use cases that are all about small and reliable. Is anything stopping this from being scaled-up to be a light but very powerful engine for a sports or supercar? This could be a huge innovation in racing if it scaled.

tacroqueen• 3 years ago

I don't think New Atlas is a reputable site.

https://medium.com/democratizing-finance/liquid-piston-insid...

This is likely all part of a pump and dump. That's why it's a weird article.

They've been advertising this heavily of all places on instagram and taboola chumboxes. Obviously none of those people need this engine, they're looking for marks.

jiveturkey• 3 years ago

came across this company a few weeks ago. the engine design is neat (who doesn’t have a soft spot for the wankel). while the design is neat, the scammy investors page turned me right off.

AceyMan• 3 years ago

TFA didn't seem to hint how they addressed the hot-side/cold-side issue that troubles Wankel designs. Anyone who knows more, please share.

Zigurd• 3 years ago

They were advertising on Twitter for crowdfunded investment, which is a very small-time vibe.

DesiLurker7• 3 years ago

I know this is targeted towards military/aviation applications (now, initially it was different), but, I honestly cannot understand why there is so little research on just making a hyper-efficient low-maintenance engine that runs at maybe 2 optimal rpms and powers a small battery bank plus electric motor (i.e.. typically series hybrid). None of these gas engines will come anywhere near the power-per-pound & torque output of a electric motor.

If traditional carmakers had done that research about 10 years ago they wouldn't be facing such crisis with EVs today. a high-efficiency multi-fuel range extender engine is all we need today but still I cant find many automakers jumping on it.

PS: it would have been nice to see a micro-turbine based generator with high thermodynamic efficiency but my understanding is that need a lot of maintenance so not suitable for consumer applications.

driverdan• 3 years ago

One of the reasons is government regulation. I'll talk about US regulation but similar situations exist in other countries.

1. US incentives and regulation result in car manufacturers having to shift production from hybrids to EVs.

2. In order to qualify as an EV a vehicle can't have a range extending ICE that provides more than a 50% range increase. There's also a very low limit to the size of the fuel tank.

These regulations have resulted in very few vehicles with ICE range extenders. Existing engines are easily capable of maxing out that regulation so there's no incentive to research other engines.

DesiLurker7• 3 years ago

US incentives aside, Nothing was stopping them from doing this for more expensive vehicles even if they didn't care about environment. I mean wouldn't you want to have a pickup truck with acceleration & torque of an EV with 2+1 motors powered by series hybrid and also have fuel economy of a 40mpg in city?

I think its just institutional laziness & innovators dilemma. Even in last 5 years when it was clear Tesla is starting to rise they decided to sit on their hands and do nothing. Even till last year toyota has been singing BS about hydrogen cars and not enough lithium. they deserve whats coming to them.

tda2• 3 years ago

Are you aware you are essentially describing the original Toyota Prius? the engine is optimised for constant low rpm/low torque/high efficiency, whilest relying on the battery/electric motor for torque and temporary extra power

Tade0• 3 years ago

Actually it just keeps the engine at/close to minimal brake-specific fuel consumption:

https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumpt...

Which covers a range of RPMs.

DesiLurker7• 3 years ago

yes I am well aware of Prius series configuration but it is still a regular engine shrunk down and fine tuned. What I am asking for is something very ground up redesigned for maximizing one thing only efficiency of energy conversion. couple of examples of this are Aquarius engines or [1]. basically you cut out all the unnecessary stuff and all the maintenance/repair plus cost with it. Current engines are complex because they are operating over a large range or rpms and optimizing for other factors like torque etc. the you have losses in mechanical power transfer at each stage. Cut that all out and make something thats super easy to manufacture & replace and you have added another 50 years to ICE.

1: https://www.youtube.com/watch?v=u4b0_6byuFU

raizer88• 3 years ago

Check the new mx-30 r-ev from mazda. It's a wenkel engine that power a battery pack.

davidthewatson2• 3 years ago

Surely, I can't be alone in reading this having driven an RX-7, numerous turbos, but no diesels, thinking this is EXACTLY what I need to replace the 310cc single cylinder in my BMW motorcycle that gets 70 MPG consistently, sits comfortably at 70 MPH on the highway, but is slow on the uptake in a crowded on-ramp. I remember the BMW single being a revelation because it's a single, DOHC, eats corn gas for breakfast without indigestion and has plenty of breathing room at the top end of the tach, which is unusual in single cylinders at redline, 10.5K RPM IIRC. One can only hope since one has less-than-zero mechanical engineering skills.

davidbanham4• 3 years ago

People have shoehorned diesels and wankel rotaries into BMW airhead frames. It’s possible but not for the faint hearted.

With a small frame like yours you’d probably be better served by an EV conversion if you want to go down that path.

davidthewatson2• 3 years ago

Thanks for the comment.

I don't know anyone who has done the rotary or diesel conversion, though I have driven the zero and know another designer who built an electric motorcycle from scratch. When I say from scratch, I mean sketches, solid works, chassis - the whole 9. Of course, this gets easier at the edges where wheels, handlebars, exhaust, lights, and batteries are abundant.

My daily awareness of his progress was working close to his desk at work, so I'm not sure where it's at today though I recall he was about to transition from chassis to engine at the time - 2016. He was definitely ahead of the curve. Sadly, my skills are in things that we have the luxury of pretending are not bound by the laws of physics. ;->

clort• 3 years ago

looks neat and I am in no way any kind of expert; I wonder why there is an external counterweight? It seems to me that the rotating 'piston' has hollow chambers in one side only to allow passage of gases and therefore needs a counterweight to balance it; is there a reason they cannot have some hollows in the other side but not have them connected to the burn chamber so that the piston is balanced by design, and the external weight not required?

_ea1k• 3 years ago

Kind of looks like a peanut in a Dorito. So yeah, basically the opposite of the usual Dorito-powered version.

garaetjjte2• 3 years ago

Photo clearly shows spark plugs on it, and they claim it runs on diesel, so which is it? I don't think spark ignited diesel would work very well.

CharlesW• 3 years ago

How do you know they're spark plugs and not glow plugs?

garaetjjte2• 3 years ago

Glow plugs don't have HV insulator.

LesZedCB2• 3 years ago

they also claim it runs on gas and propane and hydrogen. probably the photo is set up for only on of the 4 options?

swamp40• 3 years ago

As electrification takes off, it's a difficult time to be working on new combustion engine concepts

Turn it into a portable battery charger...

joshuaheard• 3 years ago

Too bad internal combustion engines are being banned throughout the United States.

pengaru3• 3 years ago

This motor is doomed... dirty exhaust gases exiting through part of the rotor? Only a matter of time before carbon+sludge builds up and the thing is out of balance.

This is one of those designs that works fine initially when everything is fresh.

Diesel piston engines work fine when everything is worn out and full of goo.

davidbanham4• 3 years ago

The exhaust gas recirculation valve on a modern diesel engine does exactly this. It diverts a portion of the exhaust product back into the intake manifold of the engine to achieve more complete combustion and lower emissions.

Yes, it does result in a buildup of goo in the intake. No, the engine does not run well in that state. That’s what maintenance is for. Clean out the goo every 50,000km or so and it’s fine.

Modern diesels are very reliable machines, just like modern petrol engines. They’re certainly not the robust rocks they used to be, though. High pressure common rail fuel systems, precision injectors and multi stage turbos are standard issue these days and they all require regular maintenance, clean air and clean fuel to operate properly.

pengaru3• 3 years ago

The exhaust gas recirculation valve on a modern diesel engine does exactly this

Anyone who thinks the EGR valve should be made part of the rotating assembly requiring a complete overhaul to clean out, unbalancing the assembly until that occurs, needs their head examined.

eurasiantiger• 3 years ago

I find it hilarious that an energy war makes inventions like this suddenly come out of the woodwork.

bartvk• 3 years ago

It comes out of the woodwork with a $9 million grant from the US Army, that is true. On the other hand, the article states "LiquidPiston has been working on these X-engines for nearly 20 years now, with numerous prototypes already tested in small planes (see above) and go-karts."

“Inside-out Wankel” rotary engine delivers 5X the power of a diesel

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