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

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

#121

Post by gambiting »

eggsboenk wrote: post #106
ggreer wrote: post #60

Earlier quoted context omitted.

Several reasons. First, like most of the Japanese manufacturers, Mazda bet against electric vehicles. They focused R&D on improving engine efficiency and getting their engines to run on hydrogen. If Mazda wants to make electric vehicles now, they have to play catch-up, or license key technologies from other manufacturers. Second, batteries are heavy. For sedans and mid-size crossovers, this isn't much of a problem. E…

The McMurtry Spéirling is claimed to be under 1000kg. A lightweight electric car may not be an oxymoron after all. Just some concessions to make.

Our VW e-Up is just below 1200kg and has 150 miles range from a 36kWh battery, fits two of us, baby seat, and Costco shopping. You can absolutely have a lightweight electric car, just be realistic about what you're getting.

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

#122

Post by gambiting »

lostlogin wrote: post #74
ggreer wrote: post #60

Earlier quoted context omitted.

Several reasons. First, like most of the Japanese manufacturers, Mazda bet against electric vehicles. They focused R&D on improving engine efficiency and getting their engines to run on hydrogen. If Mazda wants to make electric vehicles now, they have to play catch-up, or license key technologies from other manufacturers. Second, batteries are heavy. For sedans and mid-size crossovers, this isn't much of a problem. E…

Going with this theme, the idea of a battery car with longer range is appealing to me. However a smaller battery but quick charging would mostly remove the need. I’m not sure I want to drive around with a capacitor in the boot, but a huge battery isn’t ideal either.

That's the whole thing right - most people don't actually care about having 600 miles of range, they care about being able to "refuel" quickly. My Mercedes AMG would only do like 200 miles on a tank of fuel and I don't ever recall having any kind of range anxiety with it, because you could gain all of it back within like 5 minutes and keep going.

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

#123

Post by gambiting »

01HNNWZ0MV43FF wrote: post #103
user_7832 wrote: post #76

Earlier quoted context omitted.

It would be theoretically possible to have a small battery ("just a 60 mile/100km range, or even smaller) combined with a generator, but I don't know if markets would appreciate that.

This company Toyota started a pretty popular line of hybrid gas-electric cars, maybe 20 years ago, called Priuses. I think they sell pretty well. I see a lot of them running as taxis. The new ones can plug in and drive a few miles on the highway on pure electric before starting the gas engine.

Priuses do use the ICE to drive the wheels though, no?

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

#124

Post by seltzered_ »

sethhochberg wrote: post #16
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.

They have a pretty narrow power band (produce efficient max power at a small range of RPMs) which always somewhat limited their use for normal ICE cars, but is a pretty workable constraint for an electrical generator. So you have compact size, good power to weight ratio, and power limitations that don't really matter for range extender purposes. Lots of potential. I can't find the article right now, but I'd swear I r…

> I'd swear I remember discussion here a handful of months ago about a startup marketing a similar EV range extender engine design.

Possibly https://liquidpiston.com

Prior discussions: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

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

#125

Post by pfdietz »

_yb2s wrote: post #104
user_7832 wrote: post #73

Earlier quoted context omitted.

Apparently they really don't scale well. I found this reddit post explaining it better: > Gas turbines scale extremely poorly. They rely on small clearance between the rotating blades and the housings for efficiency. The smaller the turbine, the greater the relative clearance and the more energy is lost. Gas turbines, at least with established technology, make very little sense below 300ish HP. As a real life compari…

Thank you, I've wondered for years why we didn't have tiny gas turbine engines...

There are companies that have tried, like Capstone (formerly Capstone Turbine, then Capstone Green Energy). Capstone declared chapter 11 bankruptcy last year (since emerged and continuing under new leadership.)

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

#126

Post by dragonwriter »

user_7832 wrote: post #76
ggreer wrote: post #60

Earlier quoted context omitted.

Several reasons. First, like most of the Japanese manufacturers, Mazda bet against electric vehicles. They focused R&D on improving engine efficiency and getting their engines to run on hydrogen. If Mazda wants to make electric vehicles now, they have to play catch-up, or license key technologies from other manufacturers. Second, batteries are heavy. For sedans and mid-size crossovers, this isn't much of a problem. E…

It would be theoretically possible to have a small battery ("just a 60 mile/100km range, or even smaller) combined with a generator, but I don't know if markets would appreciate that.

Its called a series hybrid, there have been a small number of plug-in hybrids that used that design, they weren't successful in the US and are no longer in the US market. But that may not be anything particular about the technology; I wouldn't generalize from such a small set.

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

#127

Post by pfdietz »

WalterBright wrote: post #110
01HNNWZ0MV43FF wrote: post #93

Earlier quoted context omitted.

Depending on the plane and engine. Big jetliners have high-bypass turbines where they do intentionally produce a lot of torque, to spin a large compressor fan, but most of the fan air does not go through the combustion step, it's just used to react off of.

It's ironic how propeller airplanes evolved into jets for for thrust and back to propellers. (A ducted fan is still a propeller.)

We may go to unducted fans soon. The latest iteration of this concept has two sets of fans, one set of which doesn't rotate.

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

#128

Post by Prcmaker »

porphyra wrote: post #36
skellera wrote: post #8

Earlier quoted context omitted.

I don’t understand why Mazda doesn’t just make a drift-tuned electric car. You could do amazing stuff with software focused on that driving style. A true electric successor to the RX-7 would capture so much attention.

Sports cars, in general, are much loved but seldom bought.

I'm literally waiting for it, have been for quite a while. Small cars have numerous benefits over just being sporty. An electric, or even a hybrid 86/BRZ or miata would be great, but can't be compared to the mini or fiat, and while tesla might be fast, it's huge. Even with a price increase these could be more affordable than a lot of sports cars. The 86/BRZ has been a huge seller too.

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

#129

Post by philwelch »

elevatedastalt wrote: post #92
philwelch wrote: post #86

Earlier quoted context omitted.

So what do they do with the exhaust?

The reason jet engines have that sort of exhaust is because the primary purpose of the gas turbine there is to dump all the excess energy into the exhaust to make it go fast (so that the plane can be pushed ahead by the reaction force). They produce very little power, just enough to power the Auxiliary Power Unit (that manages the plane electronics, air-conditioning etc.). If you want to use a gas turbine for produci…

Other people have already mentioned the distinction between turbojets (what you’re describing) and turbofan engines, but I think there’s another inaccuracy:

> They produce very little power, just enough to power the Auxiliary Power Unit (that manages the plane electronics, air-conditioning etc.).

The APU is a completely separate gas turbine that doesn’t rely on the main engines. As a consequence, the APU on an airplane will also have its own exhaust.

> If you want to use a gas turbine for producing power, you will set it up such that most of the energy goes into the work generated, rather than the exhaust, so it would be a cooler, slower exhaust, similar to an IC-engine.

Yes, obviously. At the same time, I was under the impression that turboprops and turboshafts on airplanes and helicopters still produced enough jet exhaust to represent a safety hazard, and in those applications you would also expect that most of the energy would go into the work generated rather than the exhaust. So is it just that this residential generator is even more efficient than the main engine of a heavy-lift helicopter? Is it because it’s a less powerful machine in the first place? I could continue to speculate about this but I don’t actually know.

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

#130

Post by pfdietz »

dragontamer wrote: post #50
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…

> 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? You've got it backwards. The Prius's Atkinson engine makes low-end torque *worse*, and then relies upon the EV Motor to drive the car at low speeds (0mph to 10mph) before the ICE kicks back in. If ICE is operating, its at higher RPMs…

Isn't it a Miller cycle engine, not Atkinson? Miller cycle exploits variable valve timing to make the compression stroke effectively shorter than the expansion stroke (but reduces the amount of air being compressed, reducing power); Atkinson has some funky extra joints in the rod or crankshaft, I think.

Yes: https://en.wikipedia.org/wiki/Atkinson_cycle

However, these modern Miller cycle engines are being called Atkinson or Atkinson-Miller cycle for some reason.

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