Sparky, You've got it firing way too early.

Cheers,

Stu

The simple reason these have not caught on is because they are so inefficient. I used to own an RX7 (third gen.) and it got really lousy mileage. Fast? Yes, it was fast, but it loved gas and oil. The engine was a 1.3 liter engine that got about 16 MPG. It made V8 power (almost), but it also got V8 gas mileage. Engine torque was significantly less than a V8. The engine also burns oil as a natural part of its operation, so you need to keep an eye on the oil level all the time All things considered, if you want V8 power, then you are better off getting a V8.

Where the engine comes into its own right is on the track. Considering how small and light it is, it is an ideal engine for going around the track. The one problem it has (besides fuel consumption) is that it is extremely loud. Since there are no valves in the engine, there is nothing to impede the exhaust gas when it exits the engine resulting in a very loud exhaust note. Some racing bodies have instituited rules against the noise a car can make specifically aimed at the rotary engine cars.

My seester had one. She'd tell the gas station to fill up the gas tank and throw a case of oil in the trunk. It was fast though!

Ingersol Rand tried to make an industrial version. It was disaster. The rotors would last a few months and then an over haul.

Okay, If you really think about it, though, the Wankel Rotary is in its infancy. When the receprocating engine was first introduced, it had many flaws. Over the years, these flaws have either disappeared or gotten eaiser to repair. A good example is valve seats and leaded gasoline. Until the 70s' valve seats were softer and required lead not only for octaine boost but for the seats so they wouldn't melt or fracture. After a method of hardening the seats was developed, leaded gas became a thing of the past. The same could be true of the Wankel if more companies were involved in its design and implimentation.

That's my real question. Why with all the advantages the Wankel has over the regular engine, can't it be developed and used in place of the regular engine?

Mazda has done a great job developing the rotary engine over the years, starting in the 1960's. NSU worked on it in the 1950's. So with almost 60 years of development, it is hardly in its infancy.

For automotive use, fuel efficiency (measured in brake specific fuel consumption, BSFC) is the killer for the technology. In sports cars, where efficiency is secondary, and where light weight and "uniqueness" are important, then the engine has seen application, but Mazda never uses the engine in cars for which fuel efficiency is a key target. Many reciprocating engines already use variable valve timing for good torque and low emissions at low speeds and high. Implementing the equivalent of variable valve timing on a rotary would be extraordinarily difficult, just as it would be on a two stroke engine.

That's my real question. Why with all the advantages the Wankel has over the regular engine, can't it be developed and used in place of the regular engine?

It has been developed, and is used in place of the regular engine. However its fundamental problem, low fuel efficiency, does not have any solution in sight. Today, fuel efficiency and emissions control are the two pressing concerns in engine development, so only in applications where weight is an overriding advantage is the rotary likely to do well. Therefore, aviation use has been talked about since the 1950's and there are many homebuilt planes flying with rotary engines, but even there, fuel efficiency remains a concern, and for production planes durability and oil consumption are major concerns.

The situation is not unlike that with the two stroke reciprocating engine. The two stroke is simpler and lighter, but in today's world, fuel efficiency and emissions concerns override smallness and lightness.

Perhaps other manufacturers would become interested if Mazda demonstrated a compelling advantage with the RX series cars -- they are fine, but are no faster, better handling, more fuel efficient, or less expensive than other sporty cars. Lack of advantage in those areas tends to make the engine a less than compelling R&D project for other companies, and high oil consumption, low durability, and high overhaul cost, tend to keep the engine in the oddity class.

I remember when the talk was that the next Corvette was going to be Wankle powered. What would a four rotor engine be like in something like the American Le Mans series with prototype cars? If Mazda has brought it this far why not go to the next step and try for some serious power? Just another dream.

If Mazda has brought it this far why not go to the next step and try for some serious power?

I'd like to see something like this too. A four rotor 600 hp, carbon chassis, carbon bodied super car would be fun.

from Wikipedia:

R26B

The most prominent 4-rotor engine from Mazda was used exclusively for various Mazda-built GT cars (including the 767 and 787B) in replacement of the older 13J. In 1991 this engine in a 787B became the first from outside the U.S. or Western Europe and the first (and so far only) car with anything other than a reciprocating engine to win outright the 24 hours of Le Mans race. It displaced 2622 cc and built 700 hp (522 kW) at 9000 rpm. The engine design originates as a single 13B with: an additional rotor and housing added at each end, continually variable geometry intakes, and an additional (third) spark plug per rotor. The R26B's rotor housing can be purchased at retail from Mazdaspeed, but no internal parts are available to the general public.

I saw this engine cutaway at the Detroit auto show back then.

That is to say that I am 17 years too late. Darn. I'll go back to selling hydrogen conversion kits.

Totally off topic...... hydrogen conversion. Check out the Aeorospace Engineering & Manufacturing June 08 edition. Hydrogen electric conversion of a Dimona aircraft. Very cool!!

As stated earlier, fuel economy and emissions are the deciding factors for new engine developments. But again, some are thinking outside the box. Look at the GoEngine from www.gomecsys.com and compare its performance against current technology, and against your Rotary engine.

Actually, you may not have a big room for improvement on the Rotary apart from materials. Car enthusiasts would have fewer thingys to tinker with. The other systems give some leeway for experiment and hence, improvement, I guess.

Yes, Ken, excellent comment, but it has had nowhere near the money thrown at it as has the reciprocating piston engine.

I've always hoped that someone, another genius 'geometricist', would rework the thing to have not so many losses in the exposed areas of the working chamber. The ratio of 'cylinder wall to combustion chamber area' is way out. Plus, the expanding charge is nowhere near completed enough when the exhaust phase begins. Hasn't captured enough of the energy yet.Hence the inherent thirstiness.

So, it doesn't look, to me, that it'll ever have much more money thrown at it by way of development funds.

Full marks to Mazda for getting it to where it is though. With all of it's faults, I love it.

Cheers,

Stu.

Full marks to Mazda for getting it to where it is though. With all of it's faults, I love it.

It is a great engine. I had an RX2 demo to drive a little when I sold Mazdas briefly when right out of college. (In fact, the only reason I sold cars at all was because of the RX2.) It was a really nice car, far more refined than the RX3 (which was piston-engined and intended to be sportier). Quiet, refined, powerful, smooth, with pretty good handling for its day.

It's really pretty cool that Mazda has stuck with the engine. Given that it seems to be a labor of love, it's interesting that they seemed to be going in the direction of producing a real super car with the last RX7, but then backed off with the RX8. Mazda could have something like an Acura NSX, but a little more extreme. In a "pretty cool" sports car (or sporty car) it is hard to make a standout with a rotary. But in a pull-out-the-stops ultralight super car, you can make the case for a very lightweight engine being an integral part of the concept.

I have been a rotary enthusiast for years. Being in the mechanical engineering field, it interests me just because it's cool. As well the Rx-7 is generally a great car for it's time.

I have a favorite pic with a typical 4 cylinder engine dismantled beside a typical rotary. The difference in the number of parts is amazing.

I agree with the comments on development. If the rotary had as much money thrown at it in the last 50 years as the piston engine it would be a totally different animal by now.

Rotary engines do have their drawbacks. (Some a little exaggerated here.) But there are definite advantages as well. These are an interesting engine for home built aircraft. I've read an FAA report on a rotary that lost oil in flight. The seals failed but, due to the geometry, it was able to hold enough compression to fly and land the aircraft. I've had a 4 cyl car loose oil while I was on the freeway. I had about 5 seconds after the oil light came on before it through a rod through the wall of the engine.

It is very easy to get a huge amount of power out of these little 1.2 and 1.3 litre engines. The family daily driver is obviously not a good application for this engine. But, with it's high rpms and power it would have advantages in other applications.

As for rebuild, there are shops set up for machining and it's not that big of a deal. I opened my first rotary engine a few weeks ago and It's a lot easier and simpler than the head I just pulled off my 4 cyl car. Just the fact that there are no valves and cam shafts, not to mention all the pistons and rods, makes this easier to work with.

It's essentially a solid lobed shaft running on bushings. Squirt – bang – bang –cough and you have power. How much easier can it be?

Moller to power his air car has developed a new wankel type engine.

Here is the next contender to the "new" motor technology.

http://quasiturbine.promci.qc.ca/

This site has a lot of info regarding the Wankel and piston engine combustion problems.

A few manufacturers successfully made wankel engines of which I think Mazda was the most successful. You can even buy a model wankel engine.

It is a difficullt engine to produce but it has several problems:

Firstly the engine does not have long life due to the difficulty of sealing around the rotor. Sealing in a sharp corner is always a problem.

Secondly to remove the heat from the rotor is a severe problem and has not been solved yet.

Thirdly it seems that you cannot successfully refurbish the engine.

Although it seems to be a very simply design it is not simple to make and maintain it.

The last I heard about it was that the developers are investigating a ceramic rotor.

It is interesting that the topic of seals keeps coming up. Early Rx series had issues with seals. Since then I haven't heard of any issues with seals. Some people upgrade seals for racing but others swear by the stock seals.

Our 1985 Rx-7 is 23 years old (hey I can subtract!) with over 200,000 km on it and it runs like a top. It will sit all winter and start right up even on the crappy old gas with stabilizer in it.

The engine I tore apart a few weeks ago had a lot of KMs on it too. I got it from a guy that said he ran the oil dry and compression went down. Go figure. The seals were fine but there was scoring of the housings.

I have a 1979 engine with 150, 000 miles on it in my shop. Inspection through the exhaust ports (you can see a lot through there) tells me everything is fine. Compression is good on this engine as well.

I think the big thing with these engines is maintenance. If you treat it properly you will get a lot of reliable miles out of it. That could be said for any engine.

Considering this engine has an oil injection system that uses the engine oil, carbon build-up may be the biggest problem. I've converted my rx-7 to inject oil from a reservoir of 2cycle oil in hopes of reducing this.

Cooling? Never noticed issues in the rotary engines I've run. They rely more on the oil system for cooling than other engines so they need an oil cooler. The rotors have cavities for oil cooling as well. I must say though, I've cooked more oil in 4-bangers than rotaries.

There is a variant to the Wankel engine that was patented by an Italian inventor, Libralato Ruggero based on the Atkinson Cycle with an acronym of RACE . It appears in White Smoke (http://white-smoke.wetpaint.com/page/Rotary+Engine?t=anondon't )with some marketing details of his invention, but little commercialization has occurred since it was publicized; at least that I'm aware of.

The upside of the design seems to be improved efficiency, reduced size, reduced weight and reduced complexity as compared to reciprocating engines and a significant improvement in efficiency as compared to the Wankel. The limitations of this rotary engine seems to be similar to those of the Wankel engine: end-face sealing, wear of rotary contact surfaces( stationary & rotating) and lubrication of rotary sliding mechanisms. Perhaps use of ceramic materials (PSZ-partially stablized zirconium) for rotary components would enhance longevity and minimize the need for internal lubrication.

If anyone has further information on this rotary engine development I'd be interested to hear from you.

Just Google "Ruggero Libralato" and you'll find just about all the information available, including the address of his restaurant in Belluno.

Go to www.libralato.co.uk; this is the official company site where you can see an excellent video of the engine.

Hello railrider1972

If you want real efficiency, read about this car:PML Builds 640hp Electric MINI

0-60mph in 4.5 seconds, and more, 80+ mpg.

Kind Regards....

Hi Spark,

This dates back from 2006. Did you hear of anything that would have come out of that? (i.e. any production, price, etc)

best regards,

Hello Rick@cae

No, but if you're interested, perhaps contact the designer/makers direct.

You could place the reply here, as that would be useful.

Kind Regards....

I'll do a bit of research and get back to you...

I'd considered using PML wheel motors in my MC2 vehicle. The motors in the Mini are about $16,000 - $18,000 each (they are prototypes). Then there is the additional cost of control electronics. There would be a huge price drop in production, but even then, for a vehicle like mine the price would be too high. If scaled down to a size that reduces unsprung weight enough for good handling on rough surfaces then the torque is too low for good acceleration.

I think the original Tesla approach (a two speed gearbox -- which, oddly enough, they have not been able to get working right) or a CVT is a better approach for a reasonably-priced vehicle. No matter what the motor is, doubling the gear reduction gives you twice the torque and twice the acceleration rate for a given current (which roughly, means for a given battery pack size). Generally, the gear reduction which gives you good acceleration does not provide adequate top speed.

A method used to reduce unsprung weight in the Mini is to remove the brakes entirely, using only regen braking. In a production vehicle, there would be regulatory obstacles to overcome, as well as perceptual ones -- would people really accept having to rely on electronics to stop the vehicle under all conditions?

A Mini with 640 HP is, on the face of it, pretty silly. It's not something people are clamoring for. Many people, however, would be happy with a Mini size electric car with 64 hp. But with 1/10 the torque, the acceleration and hill climbing ability of such a car (with wheel motors and no transmission) would be, for many people, unacceptable. An inboard motor with two (or more) speed transmission, a la the Tesla, is a more reasonable approach, I think.

I think a much better display of wheel motor technology would be in a reasonable vehicle that people could imagine actually buying. Electric motor scooters use wheel motors with better integration of the motor and rim, reducing unsprung weight. Also, 35 mph is considered adequate for a motor scooter in the markets where these sell well, so the requirement for low speed vs high speed gearing is largely eliminated. In ultra low speed heavy vehicles, wheel motors make great sense, as proven in the construction equipment industry. In a car capable of 90 mph over bumpy curvy roads, I'm not sure that wheel motors make sense -- but there is room for improvement in rotor/rim integration, superconductivity(?), lighter tires, etc.

Yes, Ken , I think you're on the money here.

That FIAT 500 I mentioned in an earlier thread (????) was, we considered, very successful with the gearbox left in use. I have to say that the motor was short of torque in top gear but I'd hazard a guess that it was the only FIAT 5oo which would light up the rear tyres. First gear. Didn't do it too much as we didn't want to bust anything. The results in that little machine were hard won, then.

The other thing was that it allowed the use of the motor at it's most efficient. The speed controller was a variable resistance, and wasteful, so it was mostly better to use a lower ration and let the motor operate spinning faster and drawing less current.

Just some thoughts.

Cheers,

Stu

Hi Ken,

Thanks for the explanation; I think I understand a little better now. I just heard a video/report (all in French) that explained how we (the province of Quebec people) invested via taxes about 350 million dollars in the R&D of the wheel motor (invented by Hydro-Quebec) only to have the government sell the rights/patent to it. The PLM group is scheduled to start production on those cars late next year. The Lithium polymer battery was also developed by Hydro-Quebec and sold to a private company (at least part of it).

Funny (not really) thing is, one of our politician (Desmarais) is on the board of the 4 companies driving this project (PLM, a French power utility installing wind farms in our province, a Chinese company scheduled to build the batteries and one more I can't remember of). Damn, I'm tired of getting screwed.....

Question: Do you believe their claim is legitimate in regards to battery autonomy?

It's not the first time I read about this car and frankly, I'm puzzled as to why we seem to be able to go to both extremes (too fast & furious and too slow/short distance) but still can't find the middle ground.

Oh, we also build the ZENN car right here in Quebec (about 30 km up the road from where I live) and the car is sold in the states mostly. Why? Cause our government won't let us drive it on the roads (not safe, apparently?!?) Insane........

Thanks for listening.....

Hello Rick@cae

What a horrific price for that Zenn car.

it does appear that a person almost 6ft 5 inches in stature, such as myself, would not fit inside such a contraption, let alone be safe to drive it.

Therefore it must just be a motorised shopping trolley, for little old ladies, at an over-inflated price.

Kind Regards....

Sparky,

There's something about little old ladies and electric cars. Remember, Grandma Duck drove a Baker Electric?

Stu.

Hello Stueywright

It was not a "Baker Electric", the car was made by "Andersen Carriage Company, Dept F, Detroit, Michigan", and called: "The Detroit Electric".

Grandma Duck's car

In 1953, Grandma Duck has her first appearance in the weekly. Grandma has an old-fashioned electric car, based on a real car model, see picture at left.

Info above, from: http://inducks.org/dd50/xeng1953.html

Also refer here:

Grandma Duck's Car

Refer: goofy313g.free.fr/.../cars/grandma.html

Grandma's car is a Detroit Electric. Contrary t Donald's, it is a car that really existed.

Here are some panels from stories it appears in, by Barks, Rosa, Scarpa and other artists :see the above weblink.

Kind Regards....

Thanks, Sparky.

I always thought that I'd seen her say that she drove a 'Baker'. Mais, non.

Thanks for all the stuff you sent. I love it.

I can understand why the guy won't sell.

I must find out more about the Detroit Electric. Speed controll? How did it drive? Etc.

Thanks again,

Stu.

Sparky,

I just found out, purely by accident-weird twist of fate, that Grandma Duck ' DID drive a car made by Walter Baker.' The 1913 Baker Coupe, which could be had from The Cooke and Stoddard Co, Washington, DC.as well as others. Here.

I've overlaid some of the profiles and it's exactly the vehicle Walt must have used in his renderings. Still got a couple of old comic books here.

Walter C. Baker sold his first car to Thomas Edison, and in 1902 raced his Torpedo Kid on the track at Glenville, achieving a mile in less than a minute.

Cheers,

Stu.

What about using the lower power wheel motors and a small planetary gearset. With some careful attention, you could add a small aluminum rotor and caliper. Use the regen braking effect to keep the calipers from activating. This would give you a parking brake, emergency brake, and still allow efficient regen braking. Hope you make it work and make a fortune.

Good ideas. Of course, I'd rather just make the fortune without making it work.

Interesting thread--

I owned an RX-2 from 1971 to about 1974. Seals ran fine but it ate up its o-rings around all the bolts after a dealership radiator repair. So quiet and smooth the only way to know it was running while idling was to look at the tachometer. As others have noted, fuel economy was poorer than I expected, but I suspect a less sporty rear axle ratio would have helped a lot. Mazda had a front-wheel drive version sold in Japan but never imported here. In those years they were offering a racing version of the engine with different bearings, higher speed, supercharger, and nearly twice the horsepower. Since the various portions of the cycle (intake, compression, combustion, expansion, exhaust) were each occurring on specific areas of the chamber wall, you could tailor cooling to match need, so thermal losses were less than you would expect based on ratio of surface to volume. Also, mine met the tightest pollution codes then in existence without the need for a catalytic muffler, with inherently much lower NO_x production than piston engined cars.

I don't think this type of engine is dead yet. Consider the possibilities of combining its very small size, quietness, light weight, and ease of pollution control with a constant engine-speed application (that allows much better control or optimization of efficiency) such as in a hybrid car. Interesting.

--JMM

The local larrikin fringe around here are getting in the region of 1000hp out of these things and one of them regularly runs his to 21,000rpm.

There's some fancy engineering going on in small specialist shops, not just here but all over. Pity the mainstream manufacturers don't tap into this talent pool.

Cheers,

Stu

Stueywright,

Not surprising. remember, the output shaft rpm is what you were quoting; the rotor was turning at 1/3 of that (7,000rpm).

--JMM

JMM,

Yep, sure do. And that's what makes it remarkable. Consider the 'mechanical advantage' limitations inherent in the design. Calculate the peak pressures and the put that over the expansion ratio and you'll begin to see the problems of sealing the thing. Sealing a slug in a cylinder is relatively easy. Then there's the seal linear travel, over time. Extrapolating the calculations against a piston engine one can get an idea of the energy expended (wasted) just in stopping and restarting the piston in it's reciprocating stroke.

A twin rotor Wankel only has two power pulses per shaft rotation. An 8 cyl. ---4.

Cheers

Stu

What's all this about short engine life, sealing problems, etc? What are you guys smoking?

I drove a (13B) RX7 for many years and over 250.000km, used 15% more petrol than a friend with a Porsche 924. But my RX was faster, quieter (noisy engine, haha..) and never saw a workshop, other than for a faulty window winder. Mind you, the Porsche's windows didn't even have a motor drive. No maintenance, except plugs and filters!

Sold the car merely because I needed a station wagon and missed the Wankel dearly. The following owner added another 150000 km to the clock, with no engine problems. Just the rust got to it badly. He sold it on and the final owner ran it bone dry with a leaking radiator. So the engine had well over 400.000 kms on, before it was killed by negligence. I bet it would have done 600' easy, if oil and water was filled.

I'd buy one tomorrow if I could afford it. Trust the RX8 is also lighter on fuel. Many other Mazdas (sedan's) run with rotary's in Japan and the Wankel is very suitable for Hydrogen too.

Hats off to the Japanese engineers who took on the challenge and perfected it!

It isn't slightly less...Its more like 15% less. All that energy goes out the exhaust as heat instead of power to the wheels. There is also the air pollution problem with them too. I owned one years ago (1972) and it only got 21 mpg on a cross country trip. It was fun, but a bit of a gas eater around town. Want to learn more about the engineering uses, Look up Paul Lamar at http://www.rotaryeng.net/who.html