Report: Mazda RX-7 Returns for 2017 with 450-hp Turbo Rotary

[Topweasel]

The uneven heating, combustion flame issues, sealing issues, oil needs, etc, are not issues with a lack of development, they are drawbacks inherent with the design. They aren't just things you can hand wave away and say well, maybe we will figure out how to fix that!.

No but its not like one day engines were instantly as good as the ones we have today. Standard engines have gone through seal issues, sludge buildup issues, coolant issues, oil use issues and so on. So whats to say that if given enough time and development over lets say the next twenty years that you wouldn't find new technologies to mitigate or remove the issues we see now.

I mean just look at the evolution from carburetors, to throttle bodies, to direct injection.

Should we just write off all ICE's because inherent in their design is them taking an extremely flammable material and making it explode, therefore increasing the likelihood of an exploded engine?

 

[exdeath]

You can definitely tell the engineers and realists from the non engineers and dreamers in this thread.

Moar unobtainium makes everything better gaiz!

 

[Phanuel]

You can definitely tell the engineers and realists from the non engineers and dreamers in this thread.

Moar unobtainium makes everything better gaiz!

It certainly did in that restart the core of the earth movie!

 

[Topweasel]

You can definitely tell the engineers and realists from the non engineers and dreamers in this thread.

Moar unobtainium makes everything better gaiz!

That's just silly and don't see how this is the case. I am just asking that if wankle engines had the benefit of decades of engineering and redesigns like the typical I4 sees from most of the companies out there wouldn't it be just as likely to have come up with solutions to some of the wankles shortcomings.

I am not saying there is a miracle cure for every wankle symptom. Just saying that for example its seal issue. Which maybe a bigger issue on wankles, but has still been an issue on standard engines. I mean we used to talk about 20k mile engine breakin, to 10k breakins and a breakin oil for the first 5k miles. My latest car didn't have a breakin at all, though efficiency certainly did go up after the first 5k, the manual didn't specify to keep it under a certain RPM or even any shut down procedures to make sure the seals settled correctly. All of this happens by developing new materials for the seals and how they are mated.

So what is to stop our engine building lab experts with endless amount of money over the course of 20 years with 20+ iterations of the engine used in lets say 20 million different cars coming up with a solution for the seal.

Same thing with un-level temperatures. Maybe testing and working with different alloys you find one with enough thermal conductivity that it would mitigate a particular build up of heat in certain pockets.

This isn't unabtanium. Heck some probably have answers but they would drive the engine prices up which you would want to avoid. But if it didn't need to be available now and was a progression of the engine, like the ones we are currently driving, I don't know why the engine couldn't get from

Prone to un-level tempuratures to can lead to un-level tempuratures.
From Prone to drink oil to more likely to eat oil.
From prone to develop problems with the seals to more likely to have problems with the seals.

Obviously still trade-offs but instead of knowing you have a problem child on your hands you have an engine that could develop these issues if left un-cared for. In return you get a smaller engine that more powerful than engines 3 times their size.

I mean look at Ford 5 years ago you would never think that Ford of all the companies would be replacing their near bulletproof V8 in their trucks for a Turbo'd engine. You would see people talking about how because it's a Turbo it's inherently failure prone and they'll never last. I doubt in 5 years we will be talking about how horrible of a mistake Ford make by putting the EB in the F150.

 

[Don Vito Corleone]

Although Mazda has been the only one carrying the Wankel torch for all these years, they have had decades to develop it, and they have proven from their conventionally-powered cars that they know how to make reasonably reliable products that don't suffer from glaring deficiencies. Even so, they have never been able to make a Wankel car that didn't suffer from the same old problems. While I find the Wankel engine really interesting from an innovation standpoint, it really feels like a failed solution in search of a problem.

 

[Ferzerp]

Although Mazda has been the only one carrying the Wankel torch for all these years, they have had decades to develop it, and they have proven from their conventionally-powered cars that they know how to make reasonably reliable products that don't suffer from glaring deficiencies. Even so, they have never been able to make a Wankel car that didn't suffer from the same old problems. While I find the Wankel engine really interesting from an innovation standpoint, it really feels like a failed solution in search of a problem.

Pretty much this. It isn't an innovative new solution that hasn't had time to mature. It is an experiment that failed on mass produced vehicles due to the inherent issues with the design. When all of the evidence we have points to it being a dead end idea, claiming otherwise just strikes me as wishful thinking.

 

[Topweasel]

Although Mazda has been the only one carrying the Wankel torch for all these years, they have had decades to develop it, and they have proven from their conventionally-powered cars that they know how to make reasonably reliable products that don't suffer from glaring deficiencies. Even so, they have never been able to make a Wankel car that didn't suffer from the same old problems. While I find the Wankel engine really interesting from an innovation standpoint, it really feels like a failed solution in search of a problem.

We could go back and forth on this for a while but again your talking about an engine development in lets say the skyactive that just on its own had 10x the budget during development that the RX8 engine had. So why would one assume that Mazda could work through the issues on one engine if we know that the other engine had 10x the funding working off a more familiar design? It makes sense that Mazda would spend more on the skyactiv since it was going in cars across the whole line.

Since we know that the rotary engine doesn't get nearly as much funding by the flag carrier, why would we assume that they automatically would have already come up with viable solutions to some of the downsides, based on their success with a standard engine.

That's a pretty brazen slap in the face to all engine development over the last 20 years.

As for its use. Europe is one place I could see it being extremely useful. Since most countries tax the car based on displacement. Whether its competitive pricing or built in margin, a user friendly wankel could have field day against most consumer mid level "fun" cards. The 1.3 in the RX8 has more hp then my 2.0T and up till recently most V6s. Right there any competitor is automatically at a price disadvantage having to make an engine that displaces nearly twice as much to catch up.

 

[exdeath]

There has not been decades of engineering to internal combustion engines.

There has been decades of evolutionary progress in microprocessor performance, monitoring and emissions control, fuel delivery precision, and economical harvesting and mass production of already well known periodic elements.

None of which have to do with the basic geometry or materials of the internal combustion engine which itself hasn't actually changed in over a century. Nor is it going to. Geometry says so.

We gained understanding of fluid flow, boundary layers, cooling, compression and heat engage mechanics, etc things that were already happening before we knew, and tweaked the same basic 100 year old machine slightly.

A cylinder of the appropriate bore and stroke for the application is the most efficient in terms of volume and expansion characteristics (physics: simple machine converting random kinetic energy, called expansion, to uniform or linear kinetic energy, to ultimately drive some form of crank, or lever) outside of continuous combustion (turbine, which for other reasons is not suitable for personal passenger vehicles).

Youre scratching your head thinking of a way to revolutionize the screwdriver. You can throw millions of dollars at it and sit around thinking about it for 30 years and make it out of whatever you want and in the end it will always still ultimately just be a simple continuous lever with a dress.

Then again we dreamed of nuclear moon rockets and xray vision and ray guns too before we understood the physics. Just calling something "exotic" like component materials and dreaming they will radically improve something "somehow" just demonstrates that mystique has taken over logic.

Try understanding an engine as a simple machine or collection of simple machines and understand it's purpose and it will become clear why nothing has changed in 100 years. And also why if there was a better way it would have been "found" by now.

 

[exdeath]

Oh ...

To address the HP/L nonsense earlier, if it's such a meaningful metric go run your car with a model airplane engine. They make like 1000 HP per liter, weight nearly nothing, and rev to 30,000 RPM. It's everything HP/L advocates ever wet dreamed of.

 

[Topweasel]

There has not been decades of engineering to internal combustion engines.

There has been decades of evolutionary progress in microprocessor performance, monitoring and emissions control, fuel delivery precision, and economical harvesting and mass production of already well known periodic elements.

None of which have to do with the basic geometry or materials of the internal combustion engine which itself hasn't actually changed in over a century. Nor is it going to. Geometry says so.

We gained understanding of fluid flow, boundary layers, cooling, compression and heat engage mechanics, etc things that were already happening before we knew, and tweaked the same basic 100 year old machine slightly.

A cylinder of the appropriate bore and stroke for the application is the most efficient in terms of volume and expansion characteristics (physics: simple machine converting random kinetic energy, called expansion, to uniform or linear kinetic energy, to ultimately drive some form of crank, or lever) outside of continuous combustion (turbine, which for other reasons is not suitable for personal passenger vehicles).

Youre scratching your head thinking of a way to revolutionize the screwdriver. You can throw millions of dollars at it and sit around thinking about it for 30 years and make it out of whatever you want and in the end it will always still ultimately just be a simple continuous lever with a dress.

Then again we dreamed of nuclear moon rockets and xray vision and ray guns too before we understood the physics. Just calling something "exotic" like component materials and dreaming they will radically improve something "somehow" just demonstrates that mystique has taken over logic.

Try understanding an engine as a simple machine or collection of simple machines and understand it's purpose and it will become clear why nothing has changed in 100 years. And also why if there was a better way it would have been "found" by now.

Dude your talking like I am suggesting that they would succeed in making a warp drive out of a wankle engine engine if only they spent enough time on it. Just reading the wankle wiki, you have notes about them looking to use aluminum side walls for better thermal conductivity too help level out the heat levels across the entire engine (which might help the seals as well). But apparently none of this matters if you didn't do it 100% right the first time you might as well give up and never look at it again?

That's a real defeatist attitude.

 

[Topweasel]

Oh ...

To address the HP/L nonsense earlier, if it's such a meaningful metric go run your car with a model airplane engine. They make like 1000 HP per liter, weight nearly nothing, and rev to 30,000 RPM. It's everything HP/L advocates ever wet dreamed of.

Obviously there is a balance to it. Torque, cost of engine components at a given RPM, and so on. Just saying they created twelve years ago an engine that could at a reasonable but high rpm thats actually less stressful on components at that rpm than most engines. Create more power than an engine almost twice the size with forced induction and about 40x the development costs. That's a pretty good accomplishment if you ask me.

 

[exdeath]

Lets talk about two stroke piston engines that would make twice the power per given displacement and rev higher and smoother with less than half the weight? Sounds pretty similar...

What are the advantages of a wankel now?

The advantages you'd list are pretty much characteristic of the same advantages of a two stroke, and in fact the wankel works very much like a two stroke piston engine (no valve train, ports sealed by the rotor/piston, both burn oil by design, etc)

Just trying to illustrate there is nothing magical about it.

I've got nothing against wankels. If I had a RX-7 it would be a rotary, a 20b turbo even. I think they are neat, and superior or not, I think it's a disservice to the RX-7 to throw a piston engine into it.

But the design is for a fact inferior in many ways leading to many disadvantages that will never entirely be engineered away. That's not bad or good. Just life.

The I4 despite "decades of engineering" has issues too. Terrible balance for starters. One of those inherent things that will always be there.

 

[Wingznut]

You can definitely tell the engineers and realists from the non engineers and dreamers in this thread.

Moar unobtainium makes everything better gaiz!

Here's the problem with your statement... Good engineers don't look at a problem and write it off as "inherant, thus cannot be improved."

I work in engineering in the semiconductor industry. Every day you can read on the Internet how we can't make things smaller or faster or whatever. There's always some "wall" or obstacle that can't be overcome. But then progress happens because the engineers don't accept the same things the naysayers do.

 

[Wingznut]

The I4 despite "decades of engineering" has issues too. Terrible balance for starters. One of those inherent things that will always be there.

You don't think that quality engineering has significantly improved balance and smoothness in I4 engines over the years? Of course they have.

 

[Samus]

Rotary engines are reliable as long as you keep them oiled. A lot of the failures, especially the Turbo models, were oil related; oil starvation, leading to oil sheering and premature modifier breakdown.

 

[Railgun]

A lot of the failures, especially the Turbo models, were oil related; oil starvation, leading to oil sheering and premature modifier breakdown.

And due to kids not taking care of them, poor tunes, etc.

 

[nerp]

Mazda isn't in a financial position to lose money with a rotary RX-7. Sorry guys, not going to happen. It's no secret that they'd like to. It's also no secret that they just can't and won't.

 

[exdeath]

Here's the problem with your statement... Good engineers don't look at a problem and write it off as "inherant, thus cannot be improved."

I work in engineering in the semiconductor industry. Every day you can read on the Internet how we can't make things smaller or faster or whatever. There's always some "wall" or obstacle that can't be overcome. But then progress happens because the engineers don't accept the same things the naysayers do.

It can't be improved. It can be worked around with various solutions that let you live with it better with voluntary tradeoffs, but the problem is still there and always will be.

Example.

All I4s either live with vibration or add weight, cost, and complexity and slow revs with balancer assemblies. That's not improving or enginnering away the problem. The problem is still there and you're still living with the consequences of that inherent limitation one way or another, it cannot be fixed or "engineered away".

I guess my definition of engineering the problem away is different. I take that to mean eliminating an engineering problem altogether, permanent, so it's never a problem again. Building a failing part out of forged billet instead of cast for example, or reworking to eliminate the need for the part altogether. This isn't the same thing as inherent geometry or physics limitations that you acknowledge and incorporate into your design as an unavoidable predefined constraint and tradeoff.

In that light, wankels will always have apex seal and oil consumption issues and will always have lower torque, lower compression, poorer burn characteristics, and worse emissions than a piston engine, and uneven thermal loads, no matter how many years, dollars, or unobtainium you throw at it.

Doesn't mean they aren't viable and fun. I want build a 20b now.

 

[Topweasel]

I guess my definition of engineering the problem away is different. I take that to mean eliminating an engineering problem altogether, permanent, so it's never a problem again.

No no you didn't. I said Mitigated almost with my first post on the subject. I specifically outlined issues that they could go from "prone" to more likely to develop these issues.

You just wanted to stomp your feet on the ground that the wankle was a dead end engine because it never could be as good piston engine. I was never suggesting that it would. I was just waxing romatically about how nice it would have been if wankle engines had been given the development funds and attention that piston engines got. Because like you mentioned in that post, knowing about an issue allows you to design around it in attempt to mitigate it's impact. I also don't like your comparing the idea of better seals to unobtanium. Engineers are always getting better understanding the required tolerances on seals and their bonding agents. I still don't understand whats "unobtanuim" about thinking seals would get better?

But that's the point. I suggested they could work around the problems easier if they were pounding out different iterations on regular intervals. Nothing more than that. Yet you say that I was asking for the moon. So I don't really understand how you can turn around and state "Well I thought you were saying the problem would just go away".

that it would mitigate a particular build up of heat in certain pockets

Prone to un-level tempuratures to can lead to un-level tempuratures.
From Prone to drink oil to more likely to eat oil.
From prone to develop problems with the seals to more likely to have problems with the seals.

No but its not like one day engines were instantly as good as the ones we have today. Standard engines have gone through seal issues, sludge buildup issues, coolant issues, oil use issues and so on. So whats to say that if given enough time and development over lets say the next twenty years that you wouldn't find new technologies to mitigate or remove the issues we see now.

Part of it's weakness is that it isn't used as much so little has been done to develop tech that might make up for the shortfalls we are experiencing.

 

[Knowing]

I never kept up with it but was their a reason the RX-8 never got a turbo? I remember the RX7's with a turbo seem to work so much better than without. Almost like a diesel with and without a turbo.

The ports were designed wrong and they were chasing emissions. Turbo is ideal for the rotary from a power perspective because of how it generates heat. Unfortunately, it has a square combustion chamber so it's not as efficient at using the heat that it makes.

I'm getting tired of hearing new Rx-7 rumors without anything substantial, but the hoods on some of the Miata mules look awfully long.

 

[Howard]

Oh God, why?

Some of you mentioned that rotary cars are fun to drive. I bolded the key word there. There probably aren't too many RX7s out there with LS swaps that are any less fun to drive.

HP/L is pure bullshit anyway, so let's leave that off the table. Inferior reliability, higher oil consumption, inferior BSFC, etc. all work against the rotary.

The rotary may indeed be "smoother" than a reciprocating engine of an equivalent volume package (e.g. I4 or V6) but electric motors have them beat left and right in this field. Why not throw R&D into those, which will actually benefit way more?

The rotary has inherent problems, and spending time and money trying to fix them in the hopes that eventually they will surpass reciprocating engines just isn't smart business IMO. Especially if the only advantages they have are "smoothness" (have we measured this, by the way?) and arguably a lower weight to power ratio.

(trying to clarify something earlier) Even if apex seals just stopped failing from this day forward, it would not solve the engine's inferior fuel efficiency and oil consumption. The geometry of the engine simply does not permit it.

 

[Wingznut]

Some of you mentioned that rotary cars are fun to drive. I bolded the key word there. There probably aren't too many RX7s out there with LS swaps that are any less fun to drive.

Not fun with that front/rear weight ratio. Well, maybe for drag racing.

HP/L is pure bullshit anyway, so let's leave that off the table.

Ok, fine... I guess you can't realize that a smaller displacement also equals a smaller weight and dimension. Of course, not in all cases, but certainly in this one. A Renesis engine measures just 21"x12"x17". With an engine of those dimensions, center of gravity is very low, and front/rear weight ratio is that is as close to ideal as it gets.

The rotary may indeed be "smoother" than a reciprocating engine of an equivalent volume package (e.g. I4 or V6) but electric motors have them beat left and right in this field. Why not throw R&D into those, which will actually benefit way more?

There is no "may", there's just no question about it. As for electric motors, of course they deserve R&D. Does that mean all other engines should be ignored? Of course not.

The rotary has inherent problems, and spending time and money trying to fix them in the hopes that eventually they will surpass reciprocating engines just isn't smart business IMO.

I suppose your priorities in what you are specifically looking for in a car, depends on whether or not you feel they surpass reciprocating engines... But I don't think you'll find anyone who will claim that Rotary engines surpass reciprocating for everyone. Nor anyone who feels that Mazda is looking for that.

Cars with Rotary engines are for people looking for that specific experience. And that is a unique experience that reciprocating engines cannot provide.

 

[Howard]

Not fun with that front/rear weight ratio. Well, maybe for drag racing.

Completely irrelevant. Go do your own research and see how many ICE cars out there exist with near 50:50 balance or even rear-biased balance.

Ok, fine... I guess you can't realize that a smaller displacement also equals a smaller weight and dimension. Of course, not in all cases, but certainly in this one. A Renesis engine measures just 21"x12"x17". With an engine of those dimensions, center of gravity is very low, and front/rear weight ratio is that is as close to ideal as it gets.

No comments about your remarks on displacement, I think you don't need me to tell you about it.

With a smaller package, obviously you can mount it lower in the chassis, so that's fine. Whether or not it helps weight distribution depends on the rest of the car. Besides, boxer engines do the same thing.

There is no "may", there's just no question about it.

I'm certain that many people believe that rotary engines are in general smoother than reciprocating engines, and this would in fact be the case if compared to engines of similar size, weight, and complexity. However, by what quantifiable metrics can we prove this?

As for electric motors, of course they deserve R&D. Does that mean all other engines should be ignored? Of course not.

As exdeath so kindly mentioned earlier, is anyone trying to make two-strokes work in automobiles right now? Why or why not?

Cars with Rotary engines are for people looking for that specific experience. And that is a unique experience that reciprocating engines cannot provide.

I don't think I can disagree with you there. All I'm saying is, I think it would be stupid for Mazda to do it again. Were their previous rotary cars profitable? Any new ones won't be, if the engines are going to be inferior in every way but "feel".

 

[Wingznut]

Completely irrelevant. Go do your own research and see how many ICE cars out there exist with near 50:50 balance or even rear-biased balance.

That was in response to your example of an RX-7 with an LS engine. Of course there are ICE cars with excellent balance. I don't think anyone claimed that a Rotary was the only way to achieve that.

No comments about your remarks on displacement, I think you don't need me to tell you about it.

What remarks? I mentioned the statistic, and that it was interesting. Nowhere did I, or anyone else, say anything different.

With a smaller package, obviously you can mount it lower in the chassis, so that's fine. Whether or not it helps weight distribution depends on the rest of the car. Besides, boxer engines do the same thing.

Yep.

I'm certain that many people believe that rotary engines are in general smoother than reciprocating engines, and this would in fact be the case if compared to engines of similar size, weight, and complexity. However, by what quantifiable metrics can we prove this?

What makes cars so wonderful, are that there are a lot of things that people fall in love with that don't have to be quantifiable. Cars with incredibly similar stats can have very different feels when driving. I could even argue that the things that are not quantifiable are the most important.

As exdeath so kindly mentioned earlier, is anyone trying to make two-strokes work in automobiles right now? Why or why not?

Beats me. But if someone were to design a unique/fun 2-stroke engine, I would certainly take interest.

I don't think I can disagree with you there. All I'm saying is, I think it would be stupid for Mazda to do it again. Were their previous rotary cars profitable? Any new ones won't be, if the engines are going to be inferior in every way but "feel".

You might think it's "stupid", but that doesn't mean everyone else does... Or should.

 

[darkswordsman17]

Oh God, why?

Some of you mentioned that rotary cars are fun to drive. I bolded the key word there. There probably aren't too many RX7s out there with LS swaps that are any less fun to drive.

HP/L is pure bullshit anyway, so let's leave that off the table. Inferior reliability, higher oil consumption, inferior BSFC, etc. all work against the rotary.

The rotary may indeed be "smoother" than a reciprocating engine of an equivalent volume package (e.g. I4 or V6) but electric motors have them beat left and right in this field. Why not throw R&D into those, which will actually benefit way more?

The rotary has inherent problems, and spending time and money trying to fix them in the hopes that eventually they will surpass reciprocating engines just isn't smart business IMO. Especially if the only advantages they have are "smoothness" (have we measured this, by the way?) and arguably a lower weight to power ratio.

(trying to clarify something earlier) Even if apex seals just stopped failing from this day forward, it would not solve the engine's inferior fuel efficiency and oil consumption. The geometry of the engine simply does not permit it.

This. I love the idea behind rotary engines, but there'd be just too much work to make them viable. Wouldn't turbines be a better thing to put the development resources into? They offer the positives of rotary but even moreso and I believe are more fuel efficient (I think they're also easy to make flex fuel). Probably too noisy for a production car though, but might be a good match for a hybrid system (which sadly we missed out on from Jaguar).

If I was Mazda I'd check around and see if there's anyone willing to co-develop it with them. Maybe GM since they surely did quite a bit of development on that small displacement high revving V-8 for the Corvette (and there's been rumors that GM is thinking about a smaller, lighter Corvette, although I don't know that they'd be able to offer it significantly cheaper than the base Stingray unless they go with a cheaper engine, although maybe if they go with a pretty stripped out base they could get it closer to $40K). Porsche would be a good partner as well, a flat 4 or 6 would keep the weight low, and Porsche could offer a modern 944 or 968 based off of it.