Mazda sticks with rotary power

  • Thread starter Pebb
  • 877 comments
  • 67,624 views
R1600Turbo
I'd say that's a preview for the new 6 if you ask me. Showing the RX-Vision and then deciding to give us a 4-door Rotary similar to the RX-8 instead would be a bit disappointing.
Click to expand...
I think you're right. One of the Mazda PRs I spoke to recently said the concept Mazda is showing in Tokyo wouldn't be rotary-powered - the rumour it would was just a quote taken out of context in a news story.
 
Even if its a slim likelyhood that this is a new rotary, that car is really good looking. Looking at the concept and this new photo, there are a lot of similarities. The main differences I see are wheel arches, and that "shelf" that runs front to back are far more distinct, and the rear deck is deeper to the rear window. Be it a new 6, a rotary, or a new car altogether, this new design architecture is really good.
 
bremics
You skipped over the reliability and simplicity points. A used car salesman warned against me buying a RX-8 and my brother heard someone at the same dealership on a different another day telling another perspective buyer there's only one mechanic certified to work on rotaries in the province and he splits his time between Calgary and the States.

Jeez, despite reading up on it multiple times I still keep forgetting what you have to do on while starting it to avoid accidentally flooding the engine.
Click to expand...
The biggest issue with rotarys dying is that people dont do the correct maintenance. ive owned 2 rotors. A series 4 rx7 and my current daily drive which is the rx8. The rx8s definitely have there "issues". I havent had any touch wood but I am vigilant when it comes to maintenance. All rotaries need to be driven hard as they work best at high revs. So many issues are caused by the housings getting carboned up.

a redline a day keeps rotors happay.

also regarding flooding its simple. dont give it any gas while turning it over and always warm it up before turning it off.
 
Last edited:
Eyes Fried Open
The biggest issue with rotarys dying is that people dont do the correct maintenance. ive owned 2 rotors. a series 4 rx7 and my current daily drive which is the rx8. the rx8 definitely have there "issues". I havent had any touch wood but I am vigilant when it comes to maintenance. They also need to be driven hard. so many isdues are csused by the housings getting carboned up.

a redline a day keeps rotors happay.

also regarding flooding its simple. dont give it sny gas while turning it over and always wsrm it up before turning it off.
Click to expand...
Sadly, unless the rotaries querks that us rotards know and expect, are dealt with, the average person just won't accept the engine. Less than 4 percent of cars sold in the us are manual. If people cant be bothered to learn how to use a clutch, they wont bother to learn the eccentricities, pun intended, of the rotary.
 
Rallywagon
Sadly, unless the rotaries querks that us rotards know and expect, are dealt with, the average person just won't accept the engine. Less than 4 percent of cars sold in the us are manual. If people cant be bothered to learn how to use a clutch, they wont bother to learn the eccentricities, pun intended, of the rotary.
Click to expand...
I think alot of the rx8s that fail are autos being driven everyday cautiously. one of the biggest reasons I got my 8, was the fact it is manual. Manual boxes are dying out sadly. but I would rather not have a dodgy CVT transmission that are so common now.

Every car has issues. Its can you live with them is the question.
 
One thing I wish Mazda would have done with their rotary cars (since the beginning) was to have a separate reservoir for OMP oil. It's a pretty common & easy modification, but the benefit of injecting clean, specially formulated oil instead of ass-dirty engine oil that's been heat cycled a million times cannot really be overstated. I had modified my RX-7 to run pre-mix, but the separate reservoir is really the way to go. I guess Mazda didn't want customers looking after another fluid to top off, which I think was a mistake. It probably could have saved a lot of engines and kept the reputation of the engine more intact.
 
Eunos_Cosmo
One thing I wish Mazda would have done with their rotary cars (since the beginning) was to have a separate reservoir for OMP oil. It's a pretty common & easy modification, but the benefit of injecting clean, specially formulated oil instead of ass-dirty engine oil that's been heat cycled a million times cannot really be overstated. I had modified my RX-7 to run pre-mix, but the separate reservoir is really the way to go. I guess Mazda didn't want customers looking after another fluid to top off, which I think was a mistake. It probably could have saved a lot of engines and kept the reputation of the engine more intact.
Click to expand...
yes ive done the same for my mazdabator but why mazda hasnt yet is beyond me. mineral for the omp synthetic for the block is the best by far. but I still drop my oil every 5000km
 
Eunos_Cosmo
This quote is interesting...



But they are doing it anyway? :lol:

I'll take a Mazda 3 Re-REX based on the Kai thank you very much.
Click to expand...
Yeah, made me raise an eyebrow. I think it's the usual obfuscation of facts to give competitors the ol' razzle dazzle whilst endearing potential fans of the marque. Maybe it's related to start-up / warm-up. I don't really know how range extenders are used in current hybrids, whether they cycle on and off with short-term demand, or just stay on as long as the electron juice is low.

In any sense, a rotary must be extremely space and weight efficient, both of which are at a high premium for any electric vehicle, hybrid or no. A weight saving can potentially offset a fuel efficiency issue, especially in city driving.

Of course, the neglecting of fluids is potentially even greater a challenge with a supposedly electric car.
 
Griffith500
Yeah, made me raise an eyebrow. I think it's the usual obfuscation of facts to give competitors the ol' razzle dazzle whilst endearing potential fans of the marque. Maybe it's related to start-up / warm-up. I don't really know how range extenders are used in current hybrids, whether they cycle on and off with short-term demand, or just stay on as long as the electron juice is low.

In any sense, a rotary must be extremely space and weight efficient, both of which are at a high premium for any electric vehicle, hybrid or no. A weight saving can potentially offset a fuel efficiency issue, especially in city driving.

Of course, the neglecting of fluids is potentially even greater a challenge with a supposedly electric car.
Click to expand...

Not sure if you've seen this or not, but Mazda has been working on it for a while. I think the weight savings, compactness, and completely smooth operation are big benefits for a REX ICE.

Mazda 2 EV range extender prototype first drive review
 
Eunos_Cosmo
Not sure if you've seen this or not, but Mazda has been working on it for a while. I think the weight savings, compactness, and completely smooth operation are big benefits for a REX ICE.

Mazda 2 EV range extender prototype first drive review
Click to expand...
I hadn't read it, thanks!

It's interesting. So they essentially forego the inefficiency of part-throttle operation in a normal car by running the IC-generator at WOT, which presumably offsets the conversion losses from the generator to the battery and back to the motor.

Keen to see how something engineered from the ground up (rather than adapted) for this particular hybrid scheme fares.
 
I would really love to see a parallel hybrid rotary. I think it would be a stellar combination and a much better way of enhancing the inherent benefits of the rotary engine than turbocharging, which increases stress, heat, and further reduces low rpm response. A nice 50kw motor paired with the glorious 10,000rpm capable, 230hp Renesis would have made the RX-8 a truly great car in my opinion. The electric motor would offset basically all of the rotaries more nasty low-rpm attributes (such as excessive fuel consumption, higher emissions, flooding, and lack of torque). Electric motors and rotary engines complement each other pefectly. Both are extremely smooth and compact and operation, one makes strong torque from idle, the other makes strong torque at high rpm. It's just such a good pairing, in my opinion.
 
Eunos_Cosmo
I would really love to see a parallel hybrid rotary. I think it would be a stellar combination and a much better way of enhancing the inherent benefits of the rotary engine than turbocharging, which increases stress, heat, and further reduces low rpm response. A nice 50kw motor paired with the glorious 10,000rpm capable, 230hp Renesis would have made the RX-8 a truly great car in my opinion. The electric motor would offset basically all of the rotaries more nasty low-rpm attributes (such as excessive fuel consumption, higher emissions, flooding, and lack of torque). Electric motors and rotary engines complement each other pefectly. Both are extremely smooth and compact and operation, one makes strong torque from idle, the other makes strong torque at high rpm. It's just such a good pairing, in my opinion.
Click to expand...
I had to have a bit of a think about what this means (been away from car tech for a while), but I am somewhat inclined to agree.

Electric "torque fill" for the general tractor duties would allow for a very focused rotary engine (what they do best) without hampering practicality. The combination of total output torque can't be too difficult to control between the two sources, especially without boost complicating things - this should make for a very analogue (1:1) driving experience.

NSX-style harvesting and vectoring would be excellent as well. But the weight of batteries is a problem.
 
What have we here? Hmmmm?

Is This The Mazda RX-9 Mule We’ve Been Waiting For?

Mazda-RX-9mule-4.jpg
 
A visualization of how bad those rotaries smell. It's dumping more gas than exhaust.
 
Omnis
A visualization of how bad those rotaries smell. It's dumping more gas than exhaust.
Click to expand...
To be fair that was a not so well tuned rc engine, not a properly tuned, fuel injected 13b.
It was a really interesting video though. First time ive seen them working in such a manner.
 
Very clearly demonstrates why the shape of the ports is so critical....any combustion towards the plug area essentially does nothing in terms of producing kinetic energy/torque on the rotor face.

edit: Also can't tell if that's a peripheral port motor or not. If it's a side port motor, it's missing half of its intake ports.
 
It's peripheral on both intake and exhaust, I think.

Omnis
A visualization of how bad those rotaries smell. It's dumping more gas than exhaust.
Click to expand...
It looks crazy, but Nitromethane requires very "rich" air-fuel ratios, from memory. Having looked it up, 1.7:1 still sounds crazy. That's mostly because it contains oxygen, increasing the energy that can be extracted from a given displacement of air - so long as you can pump enough fuel in, and then burn it. Alcohols are similar, only to a lesser extent.

Rotaries have very strong tuning phenomena due to the rapid area increase when a port is opened, as compared with normal poppet valves (desmodromic actuation is used because it can generally be a little more violent). This makes them more sensitive to the acoustic tuning and port timing aspects, similar to a two-stroke. So at certain engine speeds, it'll perform beautifully, but at others it will basically be misfiring all the time and dumping raw fuel out the exhaust. That's over and above the combustion chamber shortcomings affecting low speed running.
 
Griffith500
It's peripheral on both intake and exhaust, I think.


It looks crazy, but Nitromethane requires very "rich" air-fuel ratios, from memory. Having looked it up, 1.7:1 still sounds crazy. That's mostly because it contains oxygen, increasing the energy that can be extracted from a given displacement of air - so long as you can pump enough fuel in, and then burn it. Alcohols are similar, only to a lesser extent.

Rotaries have very strong tuning phenomena due to the rapid area increase when a port is opened, as compared with normal poppet valves (desmodromic actuation is used because it can generally be a little more violent). This makes them more sensitive to the acoustic tuning and port timing aspects, similar to a two-stroke. So at certain engine speeds, it'll perform beautifully, but at others it will basically be misfiring all the time and dumping raw fuel out the exhaust. That's over and above the combustion chamber shortcomings affecting low speed running.
Click to expand...
I was a long time member of the now dead mazspeed.com, a forum for 1st gen 7's. One of the members was quite the engineer and had written a lengthy article on the subject of exhaust resonance tuning on carbureted rotaries. A fair bit of power could be "pulled" from the engine using it, especially on j, bridge and peripheral ports. Tuning was mostly done by changing header tube length, ID and wall thickness. I archived most ofnthe website since it had some really good old rotary info. I'll see if i happened to save that nugget.
Edit: i am going to go ahead and say i dont have it. I thought it was part of the facts section, but it looks likenit may have in fact been a carry over from the old forum. If the site owner ended up tossing all the forum info, its dust in the wind.
 
Last edited:
Rallywagon
I was a long time member of the now dead mazspeed.com, a forum for 1st gen 7's. One of the members was quite the engineer and had written a lengthy article on the subject of exhaust resonance tuning on carbureted rotaries. A fair bit of power could be "pulled" from the engine using it, especially on j, bridge and peripheral ports. Tuning was mostly done by changing header tube length, ID and wall thickness. I archived most ofnthe website since it had some really good old rotary info. I'll see if i happened to save that nugget.
Edit: i am going to go ahead and say i dont have it. I thought it was part of the facts section, but it looks likenit may have in fact been a carry over from the old forum. If the site owner ended up tossing all the forum info, its dust in the wind.
Click to expand...
I would venture to guess that tuning is tuning, and e.g. the great books by Prof. Blair still apply to rotaries in a broad sense, pending a little "translation" from someone with the ability.

However, all that prior experience would serve as great info as to where to start, especially in the context of the unique combustion chamber, "stroke" geometry (and thermodynamics), port shapes and timings. Such a shame that info is now gone, tuners don't generally share their "secrets".
 
I've been a member of RX-7 club since 2003 or thereabouts. I too remember articles/write ups like those. The header/ exhaust system is particularly important on a rotary engine. Tuning the primaries of the exhaust manifold just right is very critical. From every exhaust pulse there are two emissions, the actual exhaust (unburned fuel, combustion particulates, etc) and a pressure wave moving at the speed of sound. When a pressure wave reaches the end of the primary (or a tube step like you see on formula 1 headers) it reverses and travels back to the exhaust port. If you tune this length properly you, that pressure wave will be hitting the exhaust port at the exact moment the exhaust port is "opened". The pressure wave reverses again, joins with the new, outgoing pressure wave and creates a large amount of vacuum behind it, pulling the exhaust gasses out of the combustion chamber. Combine this with a similarly tuned intake manifold, and you have one damn good device at turning fuel into noise....over a very limited RPM band. The same is technically true for piston engines, but the effect is not as pronounced (excluding 2-stroke) because of the poppet valves interfering with harmonics.
 
Eunos_Cosmo
I've been a member of RX-7 club since 2003 or thereabouts. I too remember articles/write ups like those. The header/ exhaust system is particularly important on a rotary engine. Tuning the primaries of the exhaust manifold just right is very critical. From every exhaust pulse there are two emissions, the actual exhaust (unburned fuel, combustion particulates, etc) and a pressure wave moving at the speed of sound. When a pressure wave reaches the end of the primary (or a tube step like you see on formula 1 headers) it reverses and travels back to the exhaust port. If you tune this length properly you, that pressure wave will be hitting the exhaust port at the exact moment the exhaust port is "opened". The pressure wave reverses again, joins with the new, outgoing pressure wave and creates a large amount of vacuum behind it, pulling the exhaust gasses out of the combustion chamber. Combine this with a similarly tuned intake manifold, and you have one damn good device at turning fuel into noise....over a very limited RPM band. The same is technically true for piston engines, but the effect is not as pronounced (excluding 2-stroke) because of the poppet valves interfering with harmonics.
Click to expand...
Gotcha by a year! Im spyride on the "big forum." Was in mazspeed as well. I havent been active on there in some time though. Sold my FB shell and the costs of maintaining an old rotary isnt budgetable.
Out of curiosity, you happen to drive a Cosmo?
 
Rallywagon
Gotcha by a year! Im spyride on the "big forum." Was in mazspeed as well. I havent been active on there in some time though. Sold my FB shell and the costs of maintaining an old rotary isnt budgetable.
Out of curiosity, you happen to drive a Cosmo?
Click to expand...

No, I just always loved them. I was/am Starfox07 on RX-7club. Haven't posted in a long, long time, as my FB is currently holed up without an engine 1803 miles from me. I keep debating whether or not I should keep it and try to make it CA-legal. RX-8 engine swap with full emissions equipment?
 
Yeah, the Cosmo has always been a dream car for me. Along with a Repu. Before i had gotten rid of my FB, that was a swap i was considering too. The 12AT was up there on the list, but sourcing and the inevitable cost of repair of that engine is too steep for me. The Renesis is far more common, along with decent rx8 donor cars. Hell, you can get a rx8 around here from a used stealership lot for as much as importing a jdm drivetrain.
Its kinda a bummer really. I have a 12a sitting in pieces that i would love to rebuild, but the rear housing is flaked beyond serviceability. The cost of a proper rebuild kit along with a new housing, i could do a v8 swap, made m more power, better reliability and have cheaper rebuild costs as well. I could never commit such sacrilege, but i do understand why people do the swap.
 

Latest Posts

Back