With tons of R&D, could the rotary be significantly better?
 

Let's say that, hypothetically, lots of car makers decided to really push the envelope with the rotary engine, and they poured all kinds of time and money into it over, say, the next 5 to 10 years. (I know—this is not going to happen.)

I get the sense that, compared to piston engines, rotaries will always need to be revved high to develop their power. (I don't have a problem with that—I like it.)

But… do you think, with enough R&D, that the rotary would ever not drink a lot of fuel? Or do you think no, that's the nature of the beast.

Just wondering.

What I wonder is when is mazda going to get away from iron for the rotor, and use something a little more heat resistive (ie, won't heatsoak as badly)... like ceramic.

The fuel issue really lies in the lack of thermal efficiency. The thing runs bloody hot, energy that could be turned into work (torque) is being sent off as heat. Iron holds a lot of heat. Rotors are iron. And so are the endplates and intermediate plates.

Who knows.. maybe they *have* played with ceramics for this... can't say fersure, 'cause I can't recall reading any bit of info on them doing so.

Of course. The piston engine has been competitively developed for how many years now? At least a century. And, how much of an improvement has it undergone?

hmm heat .. what do you do with it?

it could charge batteries for a torquie electric motor .. but thats added weight and $

Mazda has done so much with so little! I think back to my first '71' RX2. I got half the power and worse gas mileage! If half the $$ put into piston deveopment went into Rotary WOW , where would we be now? Smaller 3-Rotors even higher reving? I here Ford is asking Mazda to come out with a new 7. So at least thats positive....

Like most things, the more R&D you put into a product the better the potential becomes.

I don't see why the Rotary would be any different.

You have any official extracts of Ford making that request to Mazda.

the rotary motor already has gone thru a ton of R&D over the years. I think 1 thing is that there isnt anyone else that makes a rotary motor....and for the most part, there is only 1 rotary power plant on the market at a time....so there is nothing to compare it to.

Lots of people try to compare the renesis to the 13brew saying "why doesnt it have more power if its the NEW rotary" ... well thats not the point of this motor and its not even closely related from a engineering stand point.

Don't know if its true. Read that comment from Ford somewere. Sorry...here say

"Don't know if its true. Read that comment from Ford somewere. Sorry...here say"


rumor and a half.


its a fact that ford tried putting the AXE to the rx8 being developed. and i quote "there is no room for a rotary engine in todays sports car market"

with a steam power recovery system like BMW is coming out with you could probably do a lot with all that extra heat as far as hybridizing, and with electric assist you'd have a lot of torque available at the lower end and still keep the high rev power which is natural to the wankel, couple that with an engine that weighs half of what a piston engine of the same size does and you have something that can be really useful.

take away the sports element, slap a small, lightweight 120hp 750cc wankel in there with a hybrid unit to assist and you have a car that is still very powerful compared to the current hybrids and that could use a lot less gas than what you see them using now. I'd put the gas mileage of such a car at around 35, maybe 40 mpg but no higher. which is about the max gas mileage the current piston engines like the 2.5 4-banger in the saturn ion gets with no hybrid.

I don't know about the wankel ever being better than the piston engine for cars, but for aircraft the engine has always held significant advantages that the piston engine can't make up for in fuel economy, and yet you still see very few wankel powered aircraft.

I've brought up the same point in another thread quite a while ago. Actually it might have been in the RX7club forum. Either way, I think that if the rotary engine had the time, money, and R&D thrown at it, it would be a much better engine than it is now.

Of course it would get better. To assume that it wouldn't would be assuming that we have reached the limits of technology. The last naturally aspirated rotary that was sold came with 160 hp and had worse emissions. Even the low powered Renesis does more far than that and it's only the next generation rotary. Look at how far piston engine technology has come in just the last 10 years. It's incredible. Engine technology has advanced more in 10 years than it had in the previous 50 and that rotary development has been in there as well.

There are ways to make the rotary lighter and more powerful right now without any yet unknown technology. All aluminum housings would bring weight down. Ceramics in the motor could reduce friction and make better use of heat which would improve efficiency and power. Direct injection could help fuel efficiency. Just little things such as better shaped exhaust ports could also make things better. Small shape changes in intake and exhaust runners in piston engines have brought about big changes. The rotary is really no different in this area.

These are things that we can already do. There is still room to develop other changes such as the rotor dush shape and potentially even dimpling it in certain areas. Mazda has altered the dish shape in the past. A 3rd spark plug helped improe efficiency in the 26B race engine so why not add it? Another technique that Mazda has only hinted at is negative split timing. The RX-8 does this at idle but it can be very effectively used to bring fuel comsumption down during cruise as well. The problem with most of these ideas is cost. It's cost that determines how good something gets vs how many compromises are made. As the costs of doing things goes down, you'll see them implemented more.

If Mazda put everything idea they had into a Renesis to make it the best it could be, people would still be mad and complain that the engine doesn't respond well to aftermarket mods. People would not be happy and would badmouth the engine. Maybe it's best if the potential is never reached from the factory.

I remember buying a used 1974 RX-4 from the Mazda dealer in Seattle in 1976.
This car had the first 13B rotary engine. It came with 130 hp. 7500 rpm redline.
Look what you have now ,a 13B with 248 HP 9500 rpm redline.
The same 80 cubic inches with almost 120 hp increase,,,OK
That sounds like an IMPROVMENT to me.
Sounds like someone at Mazda is doing ok!

I think Mazda needs to license the rotary engine to other car manufacturers. That way, it willl have more money to further develop Rotary.

Thats a great amount of hp increase but lets face it, 130hp 1974 - 2006 248hp :scratchhe

There is still alot you could do to improve the NA rotary engine, lighten it by making it all aluminum, DI for fuel economy, better port design. If we are talking about keeping it a 2 rotor and NA, then yes, there are some limits as far as power and torque are concerned, as the "stroke" of a rotary is not as easily changed as a piston engine.

You could always make all these improvements to a 3 rotor, which would make more power and torque. Instead I would suggest a hybrid 2 rotor.

The rotary has worked well as a sports car engine, but hasn't faired well as a general purpose engine for a variety of reasons. A lightweight NA rotary mated with a hybrid system could change that. the light weight nature of the rotary means that the extra weight of the hybrid system is not as much of a factor, and I bet a full hyrbid rotary weighs as much as a standard I4. This would solve the torque and fuel economy issues. I bet this is why mazda is doing this with the Mazda 5 hybrid rotary in Japan.

as a hybrid or aux power unit generator, the rotary could end up getting some serious revenge on its piston brother in the future.

There's certainly a lot left to optimize with the rotary engine.

Mazda did a very good job, but if, for example, five companies would compete in the rotary sector, we'd see a 25% increase of every positive engine attribute (efficiency, durability, performance, ...) in no time.

Just to clarify, I posed the question because I was wondering if the rotary, compared to other engine designs, inherently has limitations that make it ultimately not worth pursuing as a power source for lots of cars.

Obviously any engine technology can be "improved"; I'm sure the steam engine from a Stanley Steamer or Chrysler's turbine engines from the '60's could be improved today, yet you don't see anyone bothering with those because, I assume, they could not be improved enough to make them viable alternatives to the traditional piston engine. Similarly, it seems many believe the pure "electric car" can't compete without huge advances in battery design. So I was wondering if, ultimately, the rotary—by design—would be lumped with those technologies regardless of how much R&D it enjoyed, used only as a "niche" design for cars like the RX-8.

(Gee, how obvious is it that I am not an engineer?)

I thought that was where you were going with this in the first place...

Because of the shape of the combustion chamber and the low compression ratio, rotary engines are inherently less thermodynamically efficient than piston engines. This means that a rotary will consume more gas and have worse emissions than a similar sized piston engine.

Personally, I think the quasiturbine engine has much more potential than the rotary, since it combines the good things about the rotary and the piston engine into one package. However, we are probably a couple decades away from seeing a production quasiturbine engine.

It is kinda difficult to sit here and say what is and what isn't possible with a rotary engine. The way it looks right now (especially with increasing fuel prices), I would say that the rotary will never be a competitor with the piston engines, just because it is so inefficient.

It's very probable that this will happen, at least for car engines, unless the fuel consumption can come to equal that of piston engines. I still insist though that the 13B is now too big and powerful for it's pants, and a smaller wankel engine should be developed for smaller cars with a CVT tranny.

the 13B will always be a sports car engine.

The wankel also has the potential to run on hydrogen, that gives it a future past the piston engine, but hydrogen is already a controversial subject in of itself.

I'm an engineer, albeit not a mechanical engineer... but the quasiturbine seems to me like the ravings of a mad frenchman. having read his website about the engine, I find he talks to you in roses and strawberries while keeping objectivity squashed. I read a discussion on the quasiturbine on a mechanical engineer's forum and the consensus was that it's not a practical concept.

It is doubtful that the other major car companies (particularly the US companies) would be interested in heading off on another tangent with rotary technology any time soon. Some of them did license the technology years ago, did some development and testing, and decided it was not something that was in their best bottom-line interest to continue with. So, at least the US manufacturers are unlikely to jump back into the fray with expenditures of large sums of money on R&D of an entirely new (to them) technology. Especially when some of them are closing plants and laying off employees.

Maybe some of the other Japanese and possibly European companies with deep pockets might be interested, but I even doubt that. Remember that for most consumers, the rotary engine is something alien and human nature is to avoid the unknown. It would take a major "educational" campaign to even begin to move the rotary-engined car into the "mainstream", so most manufacturers just ain't gonna go there.

Before the 'efficiency' thing gets out of hand -- yes, the Renesis is a little worse off than say a 3 liter v6 in terms of MPG, but not *that* far behind. Mazda has done a remarkable job in squeezing atmospheric power out of the 13b, thanks to the new sideporting and more refined intake (compared to the DESI).

Direct Injection may bring more efficiency gains, and maybe one day a Mazda engineer will patent Unobtanium, and we'll have a thermally-efficient rotary engine ;)

I hope mazda keeps working it. Dont' stop. '95-03 was a sad, dry time in my life... no new rotaries. Don't let that happen again. :)

I'd still love to see a rotary in a Mazda3 (driving the front wheels, of course). It would have been awesome to have the Mazdaspeed3 be rotary :D

I think the Rotary has plenty of headroom for development.

As far as the fuel efficiency dooming it in the future.... that all depends on how many people are willing to take that hit to their wallets to enjoy the benefits. Obviously, right now, despite high gas prices, there is still a robust community based around the rotary. Assuming that Mazda will continue to advance the design (whether through exotic materials or more mechanical means), I'd say the rotary engine should essentially keep pace with the piston variety.

The RX-8 has been a critical, and sales, success, both globally and in America. That makes a pretty compelling business case for continuing the rotaries development.

Short answer: I think the rotary will last nearly as long as the piston engine.

Mazda *had* a 13A -- specifically for FWD applications.. went nowhere, tho. It was for the Familia FWD (GLC/323)

As for gas prices... feh. Hasn't killed the SUV, so I don't think that'll kill the wankel either...

I'm still tryin' to figger it out. 1974 same thing happened, gas went through the roof, the muscle car died, the big yanktanks died, Mazda almost died, since just about everythign they had back then had a wankel in it.. everyone was buying little cars... now, 30 years later.. what's the diff? Why aren't folks ditching their SUVs in a mad rush?