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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

#271

Post by wkat4242 »

adrianN wrote: post #202
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)

Why would you burn hydrogen in a car? It's more efficient to burn it in a power plant and run the car on electricity.

I'm sure there's some niche uses where it makes sense. Fast refueling for example because batteries are so slow. And much heavier than a Wankel engine plus hydrogen tank.

Like in a public transport bus that needs to be on the go all day. In fact I'm pretty sure that's what the hydrogen buses in my city do, they're way too noisy to be fuel cell electric.

Besides, if you can run on electric you can bypass the whole hydrogen step altogether.

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

#272

Post by seabrookmx »

TylerE wrote: post #260
seabrookmx wrote: post #209

Earlier quoted context omitted.

I'm not saying rotaries are great, but two stroke piston engines can have variable port timing (typically called a "power valve"). I don't see why the same method couldn't be applied to a rotary.

The same reason we don’t use two strokes anymore? They’re environmental disasters and wildly inefficient.

The comment I replied to said a rotary couldn't have variable timing and so I was simply refuting that claim.

I'm not trying to make a case for either engine here.. there's clear reasons why four cycle piston engines won out for the most part (other than a few powersport and power equipment niches).

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

#273

Post by smileysteve »

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.

Mazda implemented "auxiliary ports" in the fb to Fc transition ~85, the 5th and 6th ports were vacuum actuated rotating sleeves that increased intake volume and duration; this was available before VTEC and Variocam.

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

#275

Post by Supermancho »

nogridbag wrote: post #183
Supermancho wrote: post #181

Earlier quoted context omitted.

I had an RX-8 for years. It was made in 2007. Someone defaulted on the loan or lost it in a divorce and drove it into a lake, marking it salvage. I bought it for 25k and was the owner from 2009 to 2019, from 60k to over 150k mi. The maintenance was a bit pricey, due to the fuel injection problems and the electronics would fail in extreme heat of sustained 110+ outside temp (southern california heat) or cold (seattle…

Wait you paid 25k for a used/salvage RX-8 in 2009? That sounds crazy. I think I bought one new for around 26k in 2008.

A new RX8 Gran Touring in 2009 was ~38k out the door, iirc.

I completed the purchase of one red new gran touring from Mazda, for delivery. The inventory was already taken, so they tried to swap a yellow and I cancelled. The next shipment was in another 8 months. Obviously, the internet RX8 community was active and I knew what was a reasonable pricing, at the time. I looked locally and I had a salvage checked out at Mazda. It was clean. As I mentioned, I sold it to a collector for 9k ~10 years later, as it was still in near-mint condition, regardless of the title status.

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

#276

Post by jqpabc123 »

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…

Once you discover a hammer, everything looks like a nail.

There are better designs than Wankel for "series hybrid" application.

https://newatlas.com/automotive/innengine-one-stroke-engine-...

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

#277

Post by unfoldedCravat »

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.

Mazda has a super interesting way of doing this. When paired with an electric motor/generator, they can speed up/slow down specific parts of the combustion cycle to essentially get vvt. I think they can only really do this as a range extender due to the fact it makes power delivery a little bit weird.

https://carbuzz.com/news/mazdas-new-rotary-engine-variable-v...

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

#278

Post by whaleofatw2022 »

jeffbee wrote: post #63
aidenn0 wrote: post #53

Earlier quoted context omitted.

I am mildly annoyed that Toyota calls late intake valve closing (LIVC) an "Atkinson-cycle" Atkinson made 3 engines none of which are anything like a 4-stroke with LIVC. The closest is perhaps his two-stroke engine, which kept the exhaust valve closed during the power stroke and open for part of the compression stroke. The Miller-cycle is much closer to what the Prius uses than anything Atkinson made; it was a traditi…

And, of course, Mazda had been selling LIVC engines for years before the Prius appeared. Like all of Mazda's other weird engines they were expensive, bad, and unreliable.

I was gonna say, pretty sure the millenia? Had some sort of Miller cycle

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

#279

Post by rootusrootus »

lightedman wrote: post #269
rootusrootus wrote: post #263

Earlier quoted context omitted.

Could you elaborate on why this is? Naively, the temperature of a simple hydrogen flame is not too much hotter than a methane flame. And in torch form, it seems like MAPP is several hundred degrees (C) hotter? And oxy-acetylene a few hundred more on top of that. Any torch seems to have way more than enough heat to melt platinum (1700C)?

A hydrogen-oxygen flame (this is what happens naturally since you're burning hydrogen in open atmosphere) burns closer to 2800C, and also has the fun property of causing embrittlement (which is especially worsened at higher temperatures where metal expands and becomes more porous.) Your steel pots and pans are essentially toast under a hydrogen flame. People think "Fire is fire" and no, no it is not.

When I was doing a bit of research, I was coming up with 2050C or so for hydrogen open flame (in air; with pure oxygen it was 2600C), and about 1950C for methane in air. Natural gas is mostly methane and has a pretty similar flame temperature, but it does not melt our pots and pans. Why would hydrogen? It is hotter, sure, but not dramatically so.

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

#280

Post by aitchnyu »

Baeocystin wrote: post #137
avalys wrote: post #100

Earlier quoted context omitted.

What's your point? There's no reason to have a generator that charges the pack in a hurry. It really only needs to cover the maximum sustained average draw - driving up an extended grade at high speed. That's a lot less than 300 hp - it's probably not more than 80 hp or so at most.

I remember back in the 90's in auto shop we calculated that you'd only need 15-25hp continuous to essentially power all of a car's needs if you could smooth demand for power from the peaks over the length of the trip. It stuck with me as a surprisingly small number, but it mathed out, even including heating and AC. Cars are both larger and more aerodynamic nowadays; I wonder if the amount would still be the same?

Will car owners be allowed to run their (25 hp) range extenders unattended? It could be useful to allow it to top up battery while parked, and the car could detect its in an enclosed garage.
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