Mazda sticks with rotary power
- Thread starter Pebb
- 879 comments
- 71,613 views
- 11,907
- Marin County
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
The rotary equivalent of piston speed. The higher the speed of the rotor tips, the more wear you have to deal with, the more oil you need for lubrication. The largest rotor would experience much more wear throughout its lifetime than the smaller ones simply by idling with much higher tip velocity. Plus, the larger, heavier rotor wouldn't necessarily be as happy at high rpms. It would also require a slower burning fuel than the small rotors. The natural balance of two rotors with similarly sized booms would go out the window as well. You could balance it mechanically but that takes work and weight.
- 38,953
- Application hell
- MP-Omnis
So why not put a clutch pack between the minime rotor and the power rotor(s)? Or not a clutch pack, but some sort of transmission that can couple two inputs to one output.
Honestly, they should stick to the electric cars with tiny rotary range extenders.
edit: Wow, look what I found: http://www.rotaryeng.net/RX8-TC-eng3.html
This guy pretty much lays it out. Maybe I've seen this in the past and that's where I got the idea. Anyway, it's a good read.
Honestly, they should stick to the electric cars with tiny rotary range extenders.
edit: Wow, look what I found: http://www.rotaryeng.net/RX8-TC-eng3.html
This guy pretty much lays it out. Maybe I've seen this in the past and that's where I got the idea. Anyway, it's a good read.
Last edited:
- 11,907
- Marin County
- 5,065
- Fort Worth
- That_sneaky_azN
WHAT exactly causes the rotary engine to have such terrible MPG?
CodeRedR51
Premium
- 55,319
- United States
- 38,953
- Application hell
- MP-Omnis
I'm not sure of the exact reason. Maybe it has something to do with how the flame travels in the combustion phase. All I know is that it's incredibly more efficient at higher loads. What I mean by that is if you have a 250hp engine, it's going to be much more efficient when using 200 of its available 250hp than if it were just cruising around maybe using 20. The difference in BSFC seems to be much more dramatic than piston engines. That's why the 787b that won Le Mans was fuel efficient-- it was constantly running at its torque peak. Compare that to a street car where it's pretty much never there.
That's where a range extender might be useful. The engine can be optimized to run at its most efficient. If something breaks, there aren't many moving parts-- it could be engineered to be an easy fix.
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
As it turns out, rotaries operate more fuel efficiently, though less power efficiently, at low, constant rpm. Mazda's goal with the 2 was to keep the engine around 2000 rpm at all times. Rotaries are least efficient during acceleration - the fuel required to accelerate the engine to a higher rpm vs. a piston engine is ridiculous.
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
I'm not sure where you got the idea that rotaries have particularly good BSFC. They don't. I don't know of anything that has a better BSFC at especially high rpm and high load - much more of the work gets wasted to friction and heat. That's why the best combination of fuel efficiency and practicality you can do in your street car is to accelerate around town using a high load at low rpm. I say most practical because you can only accelerate so slowly until you piss off all the traffic.
While the 787B's engine might have had better BSFC at race rpm than the piston engines of the time, that fact isn't true anymore and hasn't been for a long time. Since then, the only serious improvement has been the Renesis which improved BSFC and emissions drastically, but still became outdated rather quickly.
While the 787B's engine might have had better BSFC at race rpm than the piston engines of the time, that fact isn't true anymore and hasn't been for a long time. Since then, the only serious improvement has been the Renesis which improved BSFC and emissions drastically, but still became outdated rather quickly.
Let's look at the same engine running in different conditions. I'm not an engineer so you're on your own for the math. In my experience, an engine running at a low rpm with higher load in order to make the same power as when it is running at a high rpm with lower load will be using less fuel in the low rpm condition, despite the higher load, because much less of the energy produced is wasted to friction and heat. So Mazda has decided that the most efficient rpm for their range extender to operate is at about 2000 rpm despite the fact that it can't make all that much power there. It doesn't need to make maximum power. It needs to make effective power while using as little fuel as possible, and that low rpm gives them what they need under various engine loads.
- 11,907
- Marin County
A piston engine has a much larger moment of inertia on the crankshaft than a rotary does on its e-shaft. I think this explains a lot of their 'detriments.' Low torque and low power per unit of fuel especially. They make up for it partially by having 3x the power strokes in any given amount of time compared to a similarly sized piston engine. It's similar to how a 2 stroke is much less efficient than a 4 stroke, but can make more power because it has 2x power strokes.
CodeRedR51
Premium
- 55,319
- United States
Hey, remember the on, off, on, off, on, off, on revival rumors of another RX sports car? Yeah, they're off again.
http://www.autoblog.com/2014/11/10/mazda-ceo-no-rx-sports-car-report/
This is getting old.
http://www.autoblog.com/2014/11/10/mazda-ceo-no-rx-sports-car-report/
This is getting old.
- 5,065
- Fort Worth
- That_sneaky_azN
Knew it.
- 11,907
- Marin County
Between the larger brands (GM, Nissan/Renault, & VW especially) switching to mega-platforms that can provide an entire range of cars while massively cutting costs and smaller companies either being enveloped into other companies or pushed out all together, I'm afraid genuinely interesting cars will soon be reserved only for the mega wealthy. Nissan and Renault are planning to have more than 40 individual models on the same platform by 2020. How can Mazda compete with that?
Makes me sad.
Makes me sad.
CodeRedR51
Premium
- 55,319
- United States
16x Rotary + ND Miata coupe = WIN.
CodeRedR51
Premium
- 55,319
- United States
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
I think the rumors can boil down to the fact that the CEO is attempting to build a larger, more profitable company whereas others within the company want to be awesome. I sympathize with the CEO because Mazda needs to build more resources over several years before it can spend on a sports project they don't stand to profit much from.
Mazda is already competing very well with the larger companies. While they don't sell as much, they have expanded their brand and the new platforms emphasize efficiency much more so than anything from the bigger companies. Mazda is basically the only one who is getting lighter across the board and who has not leaned on ever-unreliable turbo technology to get results. I think in the long run we can bank on Mazda spending less on warranty and/or recall engine repairs than the large companies which will not only save them money but build an image of reliability over the long run.
Mazda is already competing very well with the larger companies. While they don't sell as much, they have expanded their brand and the new platforms emphasize efficiency much more so than anything from the bigger companies. Mazda is basically the only one who is getting lighter across the board and who has not leaned on ever-unreliable turbo technology to get results. I think in the long run we can bank on Mazda spending less on warranty and/or recall engine repairs than the large companies which will not only save them money but build an image of reliability over the long run.
- 11,907
- Marin County
Unless Mazda gets back in bed with somebody, I'm worried they won't have the production capability to stay competitive or even relevant 10 years from now, rotary or not. But it would be almost worse if they did get back in bed with somebody because the cars that "Mazda" turned out during the Ford stewardship were (with a few exceptions) wholly unremarkable and also inferior in quality compared to pre-Ford. Mazda has firmly positioned itself as a mainstream manufacturer with a single niche product, the MX-5. What happens when they are no longer viable in the mainstream market? It happened to Mitsubishi and Suzuki. It could easily happen with Mazda, no matter how good the product is.
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
All their products are niche within their respective markets. Everything Mazda makes focuses on sport/fun/excitement etc., and the new products especially have style to match. All the other brands are running on nothing but prior reputation. Mazda actually has a personality to sell, the root of which is the Miata (what the hell is an MX-5? This is America, son, it's a Miata).
Mazda is taking the correct steps to expand on their own and it is paying off. All they have to do is make sure the quality coming out of the Mexico plants doesn't fall off.
An interesting note I've experienced about the Mexico cars is that they actually have numerous detail differences from the Japan cars. Things like the windshield fluid reservoir and cap. Totally different. Various other elements my technician friend pointed out to me are totally different. A supplier issue, I assume, but it's odd they would redesign things instead of have a supplier build the same part. Also, the Mexico cars arrive at dealerships covered with dust. That's the obvious giveaway that they came from Mexico.
CodeRedR51
Premium
- 55,319
- United States
Keef
Premium
- 25,166
- Dayton, OH
- GTP_KeefRacer
- GTP Keef
Indeed. I just think it's funny that they have to take extra measures to clean the interior and engine bay before the cars go to customers. The Japanese cars don't have that problem.
- 11,907
- Marin County
Just because they are entertaining to drive does not at all mean they are niche. A typical car buyer will not see the Mazda as niche. They will crosshop a 3, Corolla, Focus, Sentra, Cruze, and Civic just the same. Mazda needs typical car buyers to survive. Mazda is fine if the game doesn't change, but they will be in serious trouble if the game does change.
- 9,401
- Western Sydney
- mustafur
Recently did a look around with some cars ill be looking as my next Uber car in the Subcompact range.
The new Mazda 2 is honestly pretty good, it dwarfs the Polo in interior room(can fit 4 adults comfortably) and it's layout is very BMW like, only issue is it's interior quality still lacks VW level of Refinement, but at the Entry Level class of car brands I have to say it's better then Toyota, Hyundai, Kia, Nissan and Suzuki in this segment.
For the money it's alot of car.
The new Mazda 2 is honestly pretty good, it dwarfs the Polo in interior room(can fit 4 adults comfortably) and it's layout is very BMW like, only issue is it's interior quality still lacks VW level of Refinement, but at the Entry Level class of car brands I have to say it's better then Toyota, Hyundai, Kia, Nissan and Suzuki in this segment.
For the money it's alot of car.
