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

#221

Post by fransje26 » Sat, Mar 30, 2024, 9:24 AM UTC

willis936 wrote: post #173

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…

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…

> I don't think there's a good reason to keep pushing down deadend reliability paths. [..] Not every novel and viable solution ends up being an enhancement.

That's a strange take.. It took decades to get reciprocating engines to be reliable, even deployed at scale. It also took decades to get jet engines reliable enough to comply with ETOPS requirements, to the point that it was long considered a pipe dream.

If it hadn't been for continuous investments over long periods of time and incremental adoptions of improved technologies, we wouldn't be enjoying any of their benefits today.

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

#222

Post by m463 » Sat, Mar 30, 2024, 9:26 AM UTC

adrianN wrote: post #201

m463 wrote: post #188

It's worth mentioning that serial hybrids, like the BMW i3 rx, might not be able to drive on the freeway on the output of their generator. That's why it's a "range extender" - at some point you have to pull over and charge. EDIT: this is a big secret that none of the marketing materials (want to) make clear. I'm uncertain the output of the wankel, but maybe with its power-to-weight it might get closer to being able t…

Does that matter in practice? What's the effective range for highway driving in these cars?

I recall the i3 rx only had about 2 gallons of gas.

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

#223

Post by Retric » Sat, Mar 30, 2024, 9:44 AM UTC

willis936 wrote: post #195

Retric wrote: post #192

Earlier quoted context omitted.

Because the engine isn’t the only thing being optimized. Suppose your options are 50 miles of effective plug in range and a 40% efficient engine or a 35% efficient engine and a 100 miles of plug in range. The second option might use a lot less gas. It’s not just the cost of batteries that’s a concern resulting in short plug in hybrid ranges. Weight is a real limiting factor when you also need a gas engine and large f…

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 fairly close to a 50 mile range difference depending on exact setup.

Alternatively you can have a smaller Atkinson engine and a larger reserve on the battery, but that also costs range while still being heavier.

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

#224

Post by agloe_dreams » Sat, Mar 30, 2024, 9:47 AM UTC

486sx33 wrote: post #2

Does it produce more low end torque verses a traditional gasoline combustion engine? If not then why is it better suited for electrical generation? Is it more efficient with less load? The article mostly makes it sound like Mazda just loves the wankle and wants to find any possibly way to bring it back - even though it has “high” emissions… so coupling it with a hybrid electric motor makes it happen.. That can’t be t…

One interesting detail is that Mazda never designed a wankel after the 90s. They have claimed since then that computer design and simulation has allowed for dramatic performance gains.

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

#225

Post by ryukoposting » Sat, Mar 30, 2024, 10:16 AM UTC

willis936 wrote: post #173

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…

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 that research to their advantage. Their engine's diminutive size means they can provide more interior space in a compact vehicle, which is one of the key benefits of an EV that you can't get with a conventional hybrid. There are innate material advantages to the rotary in this application, it's not just hand-waving.

There's nothing overly novel about series hybrids, either. Chevy proved they can deliver EV driving dynamics and efficiency with ICE convenience, even at a larger scale than Mazda appears to be targeting.

This entire comment perplexes me. I can't tell if you like what Mazda's doing, or if you dislike it.

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

#226

Post by eptcyka » Sat, Mar 30, 2024, 10:20 AM UTC

willis936 wrote: post #195

Retric wrote: post #192

Earlier quoted context omitted.

Because the engine isn’t the only thing being optimized. Suppose your options are 50 miles of effective plug in range and a 40% efficient engine or a 35% efficient engine and a 100 miles of plug in range. The second option might use a lot less gas. It’s not just the cost of batteries that’s a concern resulting in short plug in hybrid ranges. Weight is a real limiting factor when you also need a gas engine and large f…

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.

You will never be able to match the weight of a Wankel with a regular reciprocating piston engine, all other parameters being equal.

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

#227

Post by ryukoposting » Sat, Mar 30, 2024, 10:21 AM UTC

AtlasBarfed wrote: post #174

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…

What happened to the inside out rotary that was supposed to be extremely compact and would enable cheaper PHEVs? IIRC the patents were about 5 years ago.

If you're referring to Liquid Piston's "X-engine," as they call it, it's doing well. It landed a substantial military contract and will likely be used to make super compact, lightweight diesel generators.

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

#228

Post by class3shock » Sat, Mar 30, 2024, 11:19 AM UTC

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…

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.

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

#229

Post by inhumantsar » Sat, Mar 30, 2024, 12:21 PM UTC

greggyb wrote: post #171

ggreer wrote: post #112

Earlier quoted context omitted.

The McMurtry Spéirling is not street legal and it costs $1 million.

The Bugatti Veyron launched in 2005 with 1K horsepower and cost > $1M. As of last year, you could get a Dodge Challenger with 1K horsepower for While it is not a guarantee, the innovations in today's supercars do tend to become much more common with time.

I think you're drawing a lot of conclusions from that correlation.

what innovations did the Veyron introduce that the Challenger used?

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

#230

Post by deergomoo » Sat, Mar 30, 2024, 12:42 PM UTC

speedgoose wrote: post #214

I used to own the first gen electric i3 with its tiny range. I didn’t wish to have the hybrid ICE version to drive further, but I did wish for more electric range and more fast chargers along the road. Nowadays, I have a cheaper car with a lot more range, almost 4 times more in real life conditions, and plenty of fast chargers everywhere. I don’t see why I would bother with an ICE. It makes no sense for me. It’s beca…

I am a big proponent of EVs, but I personally think hybrids will have a really long tail, especially as the technology improves: we could feasibly end up with a situation where much city driving in a hybrid is zero-emission EV-mode.

Two reasons:

First, in relation to your point

> Once the infrastructure is good enough

I live in the UK and I think this is gonna take a long, long time here. Not only will we need to build an enormous amount of fast chargers, but there will need to a significantly greater number of them than petrol stations, to offset the fact that even the fastest chargers take 5-10x as long as filling up with petrol (2-3 mins vs 20-30).

Of course, the ideal scenario with EVs is that most charging is done at home, with fast chargers used only on long journeys. Problem is, by some estimates 2/3 of UK households do not have off-street parking. We would need to roll out en-masse solutions for on-street charging and, to my knowledge, we have not even began to think about this outside limited trials.

Second is cost. Almost all cars have got crazy expensive over the last few years (I’m unsure if the rise of the PCP is a cause or effect of this), but over here full EVs are still not affordable for a huge number of people—myself included.

I really wanted to go electric, and was looking at the MG4; widely considered to be the best value in EVs in the UK right now. But for the model with a range that would suit us, and the cost of installing a charger, you’re looking at close to £30,000. I just don’t have that sort of money, and a finance deal would be half my mortgage again. And for context, I make nearly double the median UK salary.