I don't recall seeing a thread about this, even a search does not come up with it on the first page....
Mazda has their MX-30 EV coming out this fall, right, so in 2022, they will be having a hybrid version of that. This will be a series hybrid, where the ICE is just a range extender. And that range extender is a single rotor rotary engine directly linked to a very simple generator.
I wish I could find a picture of the cutaway I have seen- which was through work. But the engine/generator is a pretty slick set up. Some of the major doubts I had for the rotary kind of go away with this- as it has to be efficient and it HAS to be clean. I guess when you heavily constrain how a rotary operates, it can be a heck of a motor.
Sonic
UltraDork
8/5/21 1:53 p.m.
This seems like a perfect rotary use case: small, light, smooth running, and constant-ish RPM can mean they put it at a range and load where it can be clean enough.
I'm curious to see what they determine is the most efficient RPM to run it, will it be at the engine's torque peak? Which presumably on a rotary is somewhere north of 4k rpm.
j_tso
Reader
8/5/21 2:09 p.m.
I got this screenshot from this video
the housing looks thinner than a 13B
Mr_Asa
PowerDork
8/5/21 2:10 p.m.
Thought this was put on hold recently?
dannyp84 said:
I'm curious to see what they determine is the most efficient RPM to run it, will it be at the engine's torque peak? Which presumably on a rotary is somewhere north of 4k rpm.
If rotaries are anything like piston engines, they are not most efficient at peak power or torque.
edit- got interrupted... knowing what I do about rotaries- unless peak torque is a lower speeds. And for this optimized version- it very well may be that.
In reply to dannyp84 :
I would expect it to be based on BSFC and emissions to select the best balance of efficiency and cleanliness.
Mr_Asa said:
Thought this was put on hold recently?
That is what I'd read on rx7club.
alfadriver said:
dannyp84 said:
I'm curious to see what they determine is the most efficient RPM to run it, will it be at the engine's torque peak? Which presumably on a rotary is somewhere north of 4k rpm.
If rotaries are anything like piston engines, they are not most efficient at peak power or torque.
edit- got interrupted... knowing what I do about rotaries- unless peak torque is a lower speeds. And for this optimized version- it very well may be that.
Rotaries are most efficient at peak load. Idle and cruise are exactly what they are really bad at, thermally and emissions wise.
All they need is an engine small enough that they can run it flat-out as necessary.
Peak torque is anywhere they want it to be, some 13Bs had peak torque in the 3000rpm range.
In reply to Pete. (l33t FS) :
How does that change with really high compression? The pictures I've seen of the motor (presumably public), the shape of the insides make it appear to have much higher compression than previous versions.
I'll have to search the web more- but the package is incredibly compact. Most of you would really like it a lot.
In reply to alfadriver :
They really can't get compression much higher than 9.4-9.7:1. The RX-8 had 10:1, but this was more to shore up part load efficiency than anything, when people put these rotors in older engines (eliminating questions of volumetric efficiency) peak power drops. It's a question of pumping losses inside the chamber as the combustion space has to get forced past the pinch.
LifeIsStout said:
Yeah, last month there was new about it being on hold- https://jalopnik.com/mazda-rotary-plans-on-back-burner-1847272169
The MX-30 website still says rotary generator is coming in 2022. Link
j_tso
Reader
8/5/21 6:24 p.m.
JNC just posted patent photos from Mazda that feature the rear of a car that looks similar to the RX-Vision concept.
It's going to be electric or hybrid, so maybe this MX-30 motor will make its way there.
ShawnG
UltimaDork
8/5/21 8:23 p.m.
If it's just running a generator, is there any reason to not use a gas turbine? They're pretty much designed to run at 100% power output, 100% of the time.
I would imagine a turbine needed to run a generator that small would be pretty compact.
In reply to ShawnG :
Emissions. Turbines make tons of NOx because of heat.
In reply to Pete. (l33t FS) :
When does an engine hit peak load ? Is there an example I could reference from day to day driving ?
In reply to ShawnG :
Also cost- gas turbines are still considerably more expensive than otto cycle engines. The rotary as it shows in pictures for this makes is very cheap.
STM317
UberDork
8/6/21 7:18 a.m.
93EXCivic said:
LifeIsStout said:
Yeah, last month there was new about it being on hold- https://jalopnik.com/mazda-rotary-plans-on-back-burner-1847272169
The MX-30 website still says rotary generator is coming in 2022. Link
The answer more or less boils down to "it's complicated".
It currently sounds like the rotary is likely to make a return in some capacity. It's likely to be used with different battery sizes (regular hybrid>PHEV> Range Extended EV). In all cases, the rotary would be used only as a generator and would not power the wheels. The different battery sizes just determine how frequently the rotary would need to run.
