161–170 of 295 posts
Instead of a Wankel, why not use a small custom turbogenerator, like the APU in aircraft?
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…
> The Wankel is at its most efficient and its most reliable when operating at a constant RPM. Conveniently, the EV generator application demands a pretty flat RPM band. If I understand the article correctly, the "series" hybrid configuration means precisely that it cannot operate at the ideal rpm when charging the battery, because it is always driving the wheels directly as well.
What was the purpose of using the rotary engine in the first place, for ICE cars? From the comments it seems it's maybe lighter for a given power output. Is that it, other than just the novelty of it?
Lighter and mechanically simpler were the selling points. Poor fuel efficiency and trouble with the seals were the downsides. My uncle had an RX-7 back in the 80s when I was a kid. I remember when it was idling I could see the exhaust puffing, in pulses. It only had a single combustion chamber after all.
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…
> The Wankel is at its most efficient and its most reliable when operating at a constant RPM. Conveniently, the EV generator application demands a pretty flat RPM band. If I understand the article correctly, the "series" hybrid configuration means precisely that it cannot operate at the ideal rpm when charging the battery, because it is always driving the wheels directly as well.
No hybrid ever runs its battery all the way to zero, and series hybrids are no exception. The Chevy Volt (the other notable series hybrid in Western markets) keeps its engine at a near-constant RPM by using the battery to supply torque, even when the battery is "dead." I would expect the MX-30 to do the same.
IME in several thousand miles driving/riding in a Volt, it hums away within a very narrow RPM band unless you hoon it on a dead battery in cold weather. Even then, it's not nearly as wide of a rev band as a conventional hybrid.
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...
https://www.smithsonianmag.com/air-space-magazine/the-little...
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I drive a 2017 Volt gen 2 and love it. I drive about 90+% of miles in EV mode and mostly use the gas engine for road trips. It is fun to drive and (other than a couple of common, and easily fixed issues) has been reliable. I do plan to replace it in the next year because it sits very low and has a very low roofline. My spouse is uncomfortable getting into it so we almost never drive it when together.
I don't understand why GM never put the Voltec drivetrain into a compact SUV. It would have sold much better than an odd looking hatchback with little interior space.
I think GM decided that the future was BEV that they would be able to come out strong with EV version of their products and sell them at reasonable prices. With the component shortages and inflation, their price targets became untenable. Then they ran into assembly problems with their battery packs so they couldn't even deliver at any price.
Now they have backtracked and said that they will bring out hybrids (maybe PHEV?). It's not clear which platform they'll use for that. I think that they have an Equinox-sized hybrid in China that they might bring over.
The flailing around EVs vs hybrids and the on again off again story on the Bolt don't make it look like they know what they are doing, sadly.
BTW the Bolt actually has a surprising about of room in it, but even so, its on the small side. Equinox would fit more customers.
Earlier quoted context omitted.
The Volt worked best as an EV with an ICE range extender. As an EV, the 40-52 mile range was sufficient for 90+% of daily driving. Adding more range would have little true benefit. It was a series hybrid, but it was mediocre as a hybrid due to the added battery weight. Nissan has the E-power hybrid that is the pure series hybrid that you describe. AFAIK it is not as efficient as a regular, parallel hybrid. The advant…
I got my honda partially because it has the closest thing to nissan's e-power (in many ways the same, but with a couple twists). At low speeds ( Now this probably isn't really accurate, but architecturally I think I like it because the only thing keeping it from being a BEV is the battery size (only a couple kWh); the electric motor is strong enough to be usable on its own. I think Toyota has increased the power on t…
GM setup the Volt to alway have full power in EV mode and the vehicle would never automatically switch to gas unless the battery was discharged.
What was the purpose of using the rotary engine in the first place, for ICE cars? From the comments it seems it's maybe lighter for a given power output. Is that it, other than just the novelty of it?
Lighter and mechanically simpler were the selling points. Poor fuel efficiency and trouble with the seals were the downsides. My uncle had an RX-7 back in the 80s when I was a kid. I remember when it was idling I could see the exhaust puffing, in pulses. It only had a single combustion chamber after all.
Just to be clear: At had two combustion chambers. Both the 12A and 13B engines had two rotors (1.2 and 1.3L "displacement" respectively), each one has a combustion chamber. I had an '84 GSL-SE (13B), I don't remember it particularly "puffing", not saying it didn't just don't remember it.
The engine in this article they say is an "8C", which I assume means 0.8L displacement.
Is the rotary better or worst with pollution ?
I have never understood why the Volt Series Hybrid idea never took off. It is more efficient to turn gasoline into electricity and then drive the car with that than to directly connect the engine to the wheels. Is it perhaps that the cost involved is just too much more than a plugin hybrid to make the small extra fuel savings worth it?
Surely the "generator -> charger -> battery -> inverter -> motor" chain is less efficient than a driveshaft. Perhaps the only benefit is the engine can run at an optimal speed, but an appropriate gear ratio should handle that.
0: https://minkara.carview.co.jp/car/nissan/note_e_power/nenpi/
1: https://minkara.carview.co.jp/car/toyota/prius/nenpi/
2: The latest one has a worse fuel economy figure than the 1st gen, by the way