Mazda’s rotary engine in the age of the electric car • Hacker News Board

Re: Mazda’s rotary engine in the age of the electric car

#241

Post by giobox » Sat, Mar 30, 2024, 3:29 PM UTC

ggreer wrote: post #212

giobox wrote: post #180

Earlier quoted context omitted.

> I agree with the adage, but brute force seems to win in this specific case. Even though it's the lightest model made, my Miata only gets 0.82g on the skidpad The current ND2 (2019+) Miata regularly pulls ~0.95 stock in magazine tests, almost identical to your model 3 Performance number. > https://www.motortrend.com/reviews/2019-mazda-mx-5-miata-clu... You can exceed 0.95 and get ~1 on an ND Miata with slightly wide…

Yes and you can modify the Model 3 to increase cornering ability, but like in the case of the Miata it means increased tire wear, worse comfort, and worse mileage. Not to mention money. My point was simply that even if you know vehicle A is twice as heavy as vehicle B, you don’t know for sure which one is faster in the turns.

> increased tire wear, worse comfort, and worse mileage… Not to mention money

It literally means none of this to change a miata as I described - we are talking a single degree of camber here not a race car. An alignment is normal maintenance - no change in price - and tires stay the same price if you go up a single size, so if you do this when getting new tires anyway it costs essentially nothing.

It’s a minor camber change (done at a standard alignment as normal, no extra special bits - just ask tech nicely). The tires will last just as long for your driving style and gas mileage unaffected. Comfort unchanged - no spring, damper or tire pressure changes.

The point this all makes is simple factors beyond weight have a huge bearing on constant lateral load car will sustain, to the point it’s almost pointless to compare weight and max corner load. You will never see car enthusiasts comparing weights of their cars and arguing in favour of more weight, almost ever. This entire comparison is pretty odd. No one who knows what they are talking about is going to question the classic Colin Chapman quote because physics didn’t change since his death - the concept of same car but lighter was faster in the 60s and 70s, and is still faster round a circuit today. It’s why race cars set faster lap times as the fuel tank depletes, which proves the point beyond doubt.

If you haven’t had a good alignment done to your NA recently get it done and don’t be scared of small adjustments, they won’t ruin anything - it does quite the opposite! - and the numbers that work great for all miatas are insanely well documented online. Steering feel will thank you for it. It’s the first thing I will have done to any generation of miata - they all benefit a lot, and usually arrive from factory not very accurately setup at all - you will see this when you have first alignment done and brand new car has initial numbers all over the place.

I’ve owned and maintained multiple examples of all four generations of the car over the last 20 years - a precision alignment with a touch more camber/toe is one of the easiest, best and cheapest (100-150 dollars typically in major US city) things you can do to the car - the miata is all about that steering feel which is easily corrupted.

Re: Mazda’s rotary engine in the age of the electric car

#242

Post by DonHopkins » Sat, Mar 30, 2024, 3:33 PM UTC

speed_spread wrote: post #17

jpgvm wrote: post #3

Earlier quoted context omitted.

Wankels can be made extremely compact so that might have something to do with it, i.e it has both very high power to weight and power to volume specs. I honestly don't know if that is the reason though, perhaps someone more knowledgeable of the specifics of range extenders might chime in but I imagine that is an important factor.

In a hybrid vehicle, the gas engine can be run mostly as a generator, which makes it possible to further optimize it for a very specific load. It's possible that such an updated+tuned Wankel could be a great fit for certain applications where space and weight are at a premium. They can simulate lots of it but to get real answers, they have to build the engine and see how it holds up. Also Mazda is a small-ish manufac…

Mazda Rotary 'Launch':

https://www.youtube.com/watch?v=Hdjj52FUsEo

>These are some of the earliest ads I wrote and directed. Many of these ads cost our client just a couple of hundred dollars. When you look at this early attempt ant animation, it's not surprising that it didn't cost much more as a decent lunch these day!

>It's hard to believe now how absolutely 'revolutionary' the rotary engine appeared to be in those days. Many of us expected that they would eventually take over from reciprocating engines completely.

>This ad was produced just before the moon landing.

>The Agency was Hayes Advertising, Sydney. My producer (and dear friend) was Max Cleary and the Account Director was Vic Violet.

Mazda RX-3 Commercial:

https://www.youtube.com/watch?v=oHzeGEHWMjo

>Piston engine goes boing, boing, boing, boing.

>Mazda engine goes Hmmmmmmmmmmmmmmmmmmmmmmmmmm.

Felix Wankel:

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

>Wankel and the Nazi Party

>During the early 1920s Wankel was a member of various radical anti-Semitic organizations. In 1921 he joined the Heidelberg branch of the Deutschvölkischer Schutz- und Trutzbund and in 1922 he became a member of the NSDAP, the National Socialist German Workers Party (or "Nazi Party"), which was banned soon afterwards. Wankel founded and led youth groups associated with a cover-up organization of the NSDAP. With them he conducted paramilitary training, scouting games and night walks.[3] When his high esteem for technical innovations was not widely shared among the German Youth Movement, he was offered instead the opportunity to talk about the issue of technology and education to Adolf Hitler and other leading National Socialists in 1928.[4]

>In the meantime Wankel's mother, Gerty had helped founding the local chapter of the NSDAP in his hometown of Lahr. Here Wankel not only rejoined the party in 1926, but also met the local Gauleiter, i.e. regional head of the NSDAP party, Robert Heinrich Wagner. In 1931 Wagner entrusted Wankel with the leadership of the Hitler Youth in Baden. But they soon fell out with each other, because Wankel tried to put a stronger emphasis on military training, whereas Wagner wished for the Hitler Youth to be a primarily political organization. In a particularly bitter and ugly controversy Wankel publicly accused Wagner of corruption. Wagner retaliated by stripping Wankel of his office by early 1932 and managed to have him expelled from the party in October 1932.

>Wankel, who sympathized with the social-revolutionary wing of the NSDAP with Gregor Strasser, then founded his own National Socialist splinter group in Lahr and continued his attacks on Wagner. Since the Nazis' seizure of power on 30 January 1933 had strengthened his position, Wagner had Wankel arrested and imprisoned in the Lahr jail in March 1933. Only by intervention of Hitler's economic adviser Wilhelm Keppler and Hitler himself, was Wankel set free in September 1933.[5] A fellow native of Baden and member of Reichstag from 1933 to 1945, Keppler had been a friend of Wankel and an ardent supporter of his technological endeavors since 1927. He now helped Wankel to get state contracts and his own Wankels Versuchs Werkstätten experimental workshop in Lindau.

>Wankel tried to rejoin the NSDAP in 1937, but was turned down.[6] With the help of Keppler, however, he was admitted to the SS in 1940 in the rank of Obersturmbannführer.[7] Two years later his membership was revoked for unknown reasons.[6]

Re: Mazda’s rotary engine in the age of the electric car

#243

Post by zrobotics » Sat, Mar 30, 2024, 3:51 PM UTC

markhahn wrote: post #239

twobitshifter wrote: post #237

Earlier quoted context omitted.

In hub motors might be another automotive example of this. They were used by Ferdinand Porsche and invented in 1896. Ever since engineers keep trying them out as a simple elegant solution. Eventually they will break through I think, but there’s the same allure in the simplicity of it all.

I admire the idea of hubmotors as well, but once mentioned them to a car engineer, who basically said "think about unsprung weight". Which, now that I think of it again, is a bit silly because most EV mass is battery, not motor.

Shaving unapeung weight down, even by a small fraction of the total vehicle weight, will dramatically affect handling and perceived ride quality. Even though the battery makes an EV heavier than an equivalent ICE car, there is still the need to reduce unsprung weight. Thus, it would be better to have the motor inboard and run a cv axle out to the wheel than have the entire mass of the motor out on the wheel.

Re: Mazda’s rotary engine in the age of the electric car

#244

Post by pfdietz » Sat, Mar 30, 2024, 4:11 PM UTC

Retric wrote: post #223

willis936 wrote: post #195

Earlier quoted context omitted.

That would be a worthy trade, but that is vastly overstating the weight of aluminum block engines compared to Li+ and not at all realistic.

Atkinson engines have poor power to weight ratio at maximum efficiency, if you’re going to maintain that 40% then the engine needs to be oversized and under utilized. This is why many hybrids have seemingly much more power than they need. Thus the 194HP Prius vs 75 HP on a CX-90 plug in SUV. Also it’s not just that you can have extra Li+ it’s also pushing around less dead weight when the engine is off. So you can get…

It could make more sense to use a conventional engine, but get extra expansion (the kind an Atkinson/Miller cycle engine gets from the longer expansion stroke) by turbo-compounding. That is, exhaust gases (still at greater than ambient pressure) go through a turbine that is coupled to the output shaft, or to another generator, rather than being used to drive a compressor as in a conventional turbo. Or, attach a motor/generator to a conventional turbo and be able to have it operate in both modes and use the battery to help overcome turbo lag.

Re: Mazda’s rotary engine in the age of the electric car

#245

Post by lightedman » Sat, Mar 30, 2024, 4:16 PM UTC

cookiengineer wrote: post #199

ryukoposting wrote: post #141

Earlier quoted context omitted.

It has nothing to do with sentimentality. Wankels have tremendous power-to-weight and power-to-size ratios. Their main problem is reliability. The generally accepted solution to improve rotary engine reliability (oil injection) results in poor emissions. The wide, flat-ish combustion chamber doesn't help the emissions problem, either. The Wankel is at its most efficient and its most reliable when operating at a const…

Technically, the Wankel rotary engine design allows much higher power output than an I-4 or even a V-6 engine design due to no strains on the rods, and much less strains on the piston(s) as those literally blow up all the time in I4 engine designs in similar power output ranges. I've seen many very reliable 3 or 4 rotary wankel swaps in RX7 FD3S that output far beyond anything imaginable any V8/V12 could produce. 200…

"The multiple use of hydrogen (e.g. a stove just needs to burn the gas)"

Oh, no. You don't want to be cooking over a flame capasble of melting platinum. You will utterly destroy your pots and pans temper. I do jewelry work, hydrogen gas is one of the hardest gases to properly work with. I'd rather let a newbie play with oxy-acetylene than a hydrogen torch.

Re: Mazda’s rotary engine in the age of the electric car

#246

Post by pfdietz » Sat, Mar 30, 2024, 4:23 PM UTC

pmsh wrote: post #177

dragontamer wrote: post #47

A good article. It barely addresses the elephant in the room however: The Toyota Prius and its Atkinson engine. The Atkinson engine is 99% the same as a regular engine (aka: Otto cycle), except the timing is different. Instead of closing the valves when the piston+cylinder is full of gasoline+air mix... the Atkinson engine waits a bit and "leaks" some gasoline+air back out before closing the intake valve, effectively…

If the engines are direct injected rather than port injected, they can just delay fuel injection until the intake valve is closed, and no fuel should be pushed back into the intake manifold. I have read that modern Toyota engines use both port and direct injection, but am not sure what the Prius does.

You want both to keep the intake valves clean, yes?

Re: Mazda’s rotary engine in the age of the electric car

#247

Post by trimethylpurine » Sat, Mar 30, 2024, 4:35 PM UTC

hatsunearu wrote: post #207

npunt wrote: post #204

I've always seen rotary engines as one of the best examples of a particular approach to design that solves something very elegantly but relies too much on one critical component where all the pressure of the design is applied. In the case of a rotary engine, it's the apex seals. They're a great warning for designers/architects/engineers to not get too enamored with the elegance of a system if parts of it are not yet…

No, rotary engines are terrible. For one, the equivalent of variable valve timing doesn't exist/cannot exist for rotary engines, unless Mazda creates a miracle. VVT and VVL lets you do some insane things in terms of efficiency and good engine behavior, so the rotary falls behind a lot. The rotor is pretty much unable to be cooled too.

I think it only turns to charge the battery, so probably it turns at it's most efficient speed at all times. Does variable valve timing help in that case?

That said, the article doesn't describe any benefit to using the rotary engine here either.

I wonder if we're missing something?

Re: Mazda’s rotary engine in the age of the electric car

#248

Post by redwall_hp » Sat, Mar 30, 2024, 4:38 PM UTC

ryukoposting wrote: post #225

willis936 wrote: post #173

Earlier quoted context omitted.

Reliability is something easily discounted because the data to characterize it is much more difficult to capture than performance data. In most applications you can work around this with redundancies and diverse technologies, but no one makes a fault tolerant powertrain due to cost. I don't think there's a good reason to keep pushing down deadend reliability paths. We should be responding to our hard earned decades o…

>In most applications you can work around this with redundancies and diverse technologies Are you proposing that Mazda should put two engines in their cars? Or am I misreading this? >hard earned decades of learning and be pressing advantages. Not every novel and viable solution ends up being an enhancement. That's precisely what Mazda is doing. They poured decades of R&D into the rotary engine, and are leveraging tha…

Formula 1 cars are also series hybrids, for about a decade now. Electric motors drive the wheels at all times, and power comes from a turbocharged V6.

Re: Mazda’s rotary engine in the age of the electric car

#249

Post by wkat4242 » Sat, Mar 30, 2024, 4:45 PM UTC

m463 wrote: post #187

wkat4242 wrote: post #179

One of the cool things about this engine is that it can run on hydrogen with minimal modifications. Not sure if the article mentions this, I don't have time to read it now. But that could make it more interesting when renewable hydrogen becomes common (right now it's not)

Have you looked at hydrogen prices? when the first hydrogen cars came out it was about $17/kg, and I think last time I looked it was around $33. I think that's a LOT more expensive than gasoline per mile.

Meh, market forces can go either way. By the time green hydrogen actually becomes available it might have changed again.

The problem is more finding a less lossy way to create it out of water with electricity.

Also I don't advocate hydrogen as a 'solution'. To me the solution is less cars and nmuch better public transport. I could see it work for buses though.

Re: Mazda’s rotary engine in the age of the electric car

#250

Post by throwaway11460 » Sat, Mar 30, 2024, 5:00 PM UTC

runlaszlorun wrote: post #233

class3shock wrote: post #228

Earlier quoted context omitted.

I would just add that sometimes ideas exceed the technology of their time. So revisiting a design that had deficiencies (weak points, high production costs, bad emissions, etc.) with new tools, materials, etc. can lead to breakthroughs. Not that that's what is happening here, just why some ideas that previously didn't work seem to circle back around.

I feel like software is the poster child for this. My hunch is that a lot of techniques have been dropped for performance penalties that may be on the order of 20-30% (totally guessing here) when Moore’s Law often has covered that gap in mere months. I read a comment on HN a while back that you can look like a genius in software by going back about 10 years and finding something forgotten. The whole web development s…

This factoid about web dev misses the fact that the JS developers today are often the same people who were writing CGI, Perl and PHP, some of us also ASP and later ASP.NET, or some Java. We always knew there are good parts about the old ways and merging the two was always the goal - it just takes some time to get the client side right and then to get the merging right.

This especially applies to React core devs. Remember XHP?