Piston engine goes boing-boing-boing, but the rotary goes hmmmmmmmm

January 15, 2012 5:23 PM

There has been only one mass-produced internal combustion alternative to the traditional reciprocating engine, the Wankel rotary. There has been only one auto manufacturer that has adopted the rotary engine, Mazda. After the 2012 model year, for the first time since 1967, Mazda's line-up will not include a rotary engined car.

(Note: While the RX-7 was not exported to the US after 1995, production continued in Japan until 2002)

Due to low sales, tightening emissions regulations, and rising fuel costs the RX-8 (Rotary eXport) will end production in Japan in 2012. European sales ended in 2010 with the US following in 2011.

Beginning with the sleek and futuristic Cosmo Sport 110S, Mazda's engineers in Hiroshima(youtube) have been dedicated to the cause of the spinning triangles. The compact dimensions of the engine, similar in size to a keg of beer, allowed the mounting location to be closer to the ground and nearer to the center of the car, lowering both the center of gravity and the polar moment of inertia; two desired characteristics for a sharp handling automobile. Technically, many of the RX models are mid-engine cars as the engine is located entirely behind the front axle.

Despite only having three main moving parts (the rotors and the eccentric shaft), the rotary engine had significant technical difficulties to overcome. The inefficient shape of the combustion chamber and the location of the intake/exhaust ports led to poor fuel economy. The minuscule displacement, only 1.3L for the final production model, was responsible for the low torque output of the non-turbocharged engines. And the nature of the engine required that engine oil to be injected into the combustion chamber to lubricate the rotor seals.

But despite those issues, Mazda devotedly continued production and development for over 40 years. Various models from family station wagons to pickup trucks to small buses were powered by the Mazda Wankel. The 4-rotor 787B(youtube) took the overall championship at Le Mans in 1991. But the most popular rotaries were the sports car models RX-7 and RX-8.

A concept engine was unveiled in 2007 promising to increase both fuel economy and torque while lowering emissions, but R&D budgets have been strained since Ford's departure as a part owner of Mazda. While Mazda claims that development continues on the 16X engine, no announcements regarding production models have been released.

There is some hope for the future of the rotary even without the 16X. The architecture of the engine makes it a prime candidate to be run on hydrogen. Also, the compact design and ability to run smoothly at high RPM open up possibilities for a series hybrid rotary-electric drivetrain.

Most of Mazda's Wankel cars were love-em-or-hate-em, and none of them compared well to their contemporaries by the numbers. But anyone who wonders whether or not a car could have a soul has never driven a rotary.

posted by hwyengr (72 comments total)

Nooooooooooooo! I love the wankel engine, mainly because watching videos of how it works is memorizing even though it's insanely inefficient.
posted by glaucon at 5:26 PM on January 15

Obviously, this is completely irrelevant to your fine post, but I cannot read "Wankel rotary engine" without hearing it in the voice of John Cleese.
posted by williampratt at 5:28 PM on January 15 [41 favorites]

Who needs the RX8 when you could drive the much more fun Mazda3speed.
posted by humanfont at 5:32 PM on January 15 [1 favorite]

The RX-8 is a fantastic car. Not the most reliable, nor very economical, but a lot of fun.

Easy to work on, not a lot of bells and whistles, not terribly expensive. A four-seater, thanks to the sucide doors.

A 1.6 liter engine would be a beast!

Some lunatics convert 2-rotor RX8s (and RX7s?) to 3-rotor 2 liter engines from long defunct japanese-market sedans.

Anyhow, carry on.
posted by etherist at 5:33 PM on January 15

I've known quite a few RX-7 owners and they all had nothing but complaints about the rotary engine. Whether it was the fuel efficiency, the constant need for oil top-ups, or the repair frequency and cost, every one eventually came to hate it.
posted by rocket88 at 5:35 PM on January 15

RX-8 driver here. When my commute increased from 8 miles each way to 30 miles, I realized that I should be driving a car that gets better than 20 MPG. But every time I drive it, it just makes me so happy. It's not fast; the new camry can outrun it to 60. But the handling is sublime. The power delivery, while not torquey, is so linear and smooth. In fact, Mazda put a buzzer into their rotary-engined cars that goes off near the RPM limiter. Apparently drivers were used to an engine sounding like it was straining or working extra hard when near the redline, and wouldn't shift their mazdas. But rotaries are meant to scream. Frequently putting them under heavy load at low rpms will build up carbon, so it's recommended that they be redlined once per day.
posted by onehalfjunco at 5:36 PM on January 15 [4 favorites]

I crave a Speed, if only I lived somewhere other than a dense city.

And the single best vehicle I ever owned was a 1989 Mazda 4x4 B2600 truck. You could not kill it by conventional means. I was still on the original damn clutch when it was finally felled at 180K miles by a falling 60 foot tree. I've even visited the Hiroshima plant. Cool post.
posted by spitbull at 5:37 PM on January 15

Another little known rotary engined vehicles here in the states were the Evinrude rotary engine snowmobiles, made back in the '70's. My father-in-law had one that ran like a top.
posted by HuronBob at 5:40 PM on January 15 [2 favorites]

Way back, my mom bought one of the original RX-3's, the first model to have the rotary engine.

It's an interesting experience driving one, because the torque curve is a lot different than for a piston engine. It's pretty much flat plotted against engine speed, and you can find yourself red-lining the engine without realizing it. If you're trying to make a fast-start off the line, you run first gear up to the red line and then shift to fourth.

Until you get used it, therefore, you really have to keep your eye on the tach.
posted by Chocolate Pickle at 5:40 PM on January 15 [1 favorite]

I thought Barney Coopersmith invented the rotary engine.
posted by Divine_Wino at 5:41 PM on January 15 [4 favorites]

The title is slightly inaccurate, btw... the piston engine goes boing, boing, boing but the Mazda goes hmmmmmmm...
posted by TheNewWazoo at 5:41 PM on January 15 [1 favorite]

I'm holding out for a consumer car with a gas turbine engine.
posted by aubilenon at 5:48 PM on January 15

.
posted by kickback at 5:59 PM on January 15

I grew up in a Mazda-loving family, and my earliest memories of a careening around in an R100 and an RX3. I gather from the gradually diminishing enthusiasm my parents displayed for these cars that the happiest day of a Mazda owner's life is the day he bought the car and the second-happiest is the day he sold it.
posted by ricochet biscuit at 6:00 PM on January 15 [1 favorite]

Oh how sad. I have the fondest memories of the 1974 RX-4 station wagon we had when I was a kid in Tennessee. Electric radioactive slime-green and I swear to god that thing was powered by rocket fuel. The speedometer went to 130 iirc, and I think the car would make it there. One of the only times I remember my mother being genuinely pissed at my father was when he made a 13 hour trip back from Florida to Tennessee with his brother in less than 8. We figured she was mad at the risks he took doing so, but on the other hand…

She didn't have too much room to talk, mind you. My mother's always been a prim and proper southern lady, but she did have an unseemly taste for speed. We'd pull up at a stop light beside a sports car, circa 1976 or so, and there'd we be, a mother with prematurely graying hair, 2 or 3 kids in the car, and we'd start in. "Come on Mom, do it."

"No, no, I really shouldn't."

But you'd see that little twitch of smile show up at the side of her mouth, and she'd rev the engine a little, just enough to get their attention, let the sports car driver know she meant business. There'd be a condescending smirk, and then the light would change green, and—holy god but that little engine could scream. Mom would blow the freakin' doors off them in her little slime-green station wagon with the kids inside it shrieking with laughter. When that little 1.1 liter engine opened up, it was like someone strapped a rocket to your ass.

Gas mileage sucked, and they were prone to burning oil, but oh so much fun. I remember too the shotgun-like blast of a backfire you'd get if you dropped the RPMs too quickly. Mom learned early on to innocently look around for the source of the noise when pulling up to a stop light and forgetting to let them down easy. "Who did that?"
posted by los pantalones del muerte at 6:01 PM on January 15 [25 favorites]

Hey, you forgot the NSU Ro 80, the other rotary-engined production car.
posted by scruss at 6:01 PM on January 15 [1 favorite]

"but I cannot read "Wankel rotary engine" without hearing it in the voice of John Cleese."

Except when I hear him say it it's Wanker.

Just curious, if it's so inefficient and technically difficult, why build it? What was the advantage?
posted by Mcable at 6:02 PM on January 15

This makes me sad; I always wanted one of the third-gen RX-7s, fickle beasts though they are. I have fond memories of sliding around Austin in the rain in the passenger seat of a turbocharged RX-7. The precision that car could produce was phenomenal, and that motor would just pull and pull and pull...

Several motorcycle manufacturers have tried rotary engines in the past:

- Suzuki, with the 1974-76 RE-5.
- Yamaha, with the 1972-73 RZ201.

And of course, the Norton F1, based on the RCW588 racebike. If you're wondering what a rotary racing motorcycle sounds like, here's two.
posted by hackwolf at 6:03 PM on January 15

all the shaking and noise in the le mans video reminded me of when it was cold and i needed to open the choke on my old first gen rx7. the le mans car didn't leave a sweet plume of blue chemtrail behind it, though.
posted by kickback at 6:03 PM on January 15

And a better link to the history of the RC588 is here.
posted by hackwolf at 6:04 PM on January 15

Well, now. This is a subject close to my heart and about which I have a fair amount of knowledge and experience.

"I've known quite a few RX-7 owners and they all had nothing but complaints about the rotary engine. Whether it was the fuel efficiency, the constant need for oil top-ups, or the repair frequency and cost, every one eventually came to hate it."

Really? Well, I never did end up owning an RX-7—something that had been my ambition for much of my adolescence and through my twenties—but I have owned, um, three different rotary engine Mazdas and I positively didn't come to "hate" the cars or their engines. And all of the things you mention were bigger problems with those earlier models, too.

"Way back, my mom bought one of the original RX-3's, the first model to have the rotary engine."

The RX-3 was not the first rotary (Wankel) engine available in any market, certainly not the US. The first in the US was the Mazda R-100 in 1971, very quickly followed by the RX-2 in 1972 and then the RX-3 later that year.

"If you're trying to make a fast-start off the line, you run first gear up to the red line and then shift to fourth."

Huh? No, that's not right. The torgue curve of the rotary is flatter than your average piston, but it's not flat. On the 12A engines that the (US) RX-2s and RX-3s had, the best part of the curve was between 5k and 8k RPMs. You'd want to keep it in that range as you work through the gears, just as you'd do with a piston. If it made sense to go from first to fourth, then it wouldn't have been geared that way to begin with.

"Just curious, if it's so inefficient and technically difficult, why build it? What was the advantage?"

It's not inefficient. It's more efficient than a piston engine. It's that you can't really make the displacement much smaller to get more efficiency out of it the way that you can with pistons. It's already an amazingly small engine.

Also, the way the history worked out, the piston engine ended up being developed enough to solve the same problems that the Wankel solved in its Mazda heyday. That is, a high power-to-weight ratio. With the increase in gas prices, first that caused piston engines to become much smaller and less powerful to save gas, then over time quite naturally there was a huge impetus to recover that lost power with improving technology. Which is what happened. So we ended up getting today's engines which are more efficient and more powerful. Wankels are still inherently more efficient, it's just that there's no real need for them in consumer automotive applications anymore.

Not the least because it is technically difficult. And the apex seal problem is a big technical problem.
posted by Ivan Fyodorovich at 6:11 PM on January 15 [5 favorites]

But you'd see that little twitch of smile show up at the side of her mouth, and she'd rev the engine a little, just enough to get their attention, let the sports car driver know she meant business.

Ah, what memories. That was my mom when she found out what the 400 under the hood of that old Ford could do. But I so wish the 77 Mazda wagon we had would have been one of the rotary models - that would have been even better.
posted by azpenguin at 6:13 PM on January 15

Mcable,

The main advantages were smaller size and lower displacement per unit of horsepower generated, as hwyengr mentioned. Additionally there's far fewer moving parts, and the parts that do move are large. 4 stroke engines have a boggling number of tiny parts that need to be exactly timed. The wankel solves these issues with the power of GEOMETRY.

Compare
http://www.animatedengines.com/wankel.html
with
http://www.animatedengines.com/otto.html
posted by kickback at 6:14 PM on January 15 [1 favorite]

I believe the R100 was the first rotary-engined Mazda sold in the U.S., followed by the RX-2.

My first car I built in the spring of 1976 from two RX-2s, a 1972 body with 1973 drive train from a nearly-new total. I bought the '72 body for $500 and the total for $330. The engine in the body had blown seals, a fate suffered by very many of those cars. I hadn't ever worked on cars but I toiled away for weeks getting the engine and transmission transferred and dealing with the fact that the wiring harness differed slightly between the two years. One day I realized that I was done and I turned the key and it started. It had a funny, loping idle that I couldn't fix but had the effect of sounding like a small block V8 with a high-lift cam. Not a bad thing for a guy in his senior year at a high-school obsessed with fast cars.

The car was copper colored and I soon changed that, painting it black with two small gold pinstripes.

Less than a year after the car was on the road, the water pump failed while I was driving it on the freeway and the resulting overheating ruined the engine, warping the housings to the point that coolant was able to leak into the chambers.

In my search for a replacement engine, I came across a local shop, Hayes Rotary Engineering, that specialized in high-performance rotary engines and, after a ride in one of their RX-3s, I was hooked and within a month or so, my car had a new engine.

For about $3000, I was the proud owner of a balanced, peripheral-ported 13B housing engine with bridge-porting, dual Webers modified with oil-injection on a Racing Beat high-rise intake manifold, hardened gears, ultra-light flywheel, tuned headers and a shot-filled scatter-shield atop the clutch bell-housing. It delivered almost 300hp in a chassis that was poorly suited for that much power but, overall, a car that was insanely fun to drive and very, very surprising to people, especially Corvette owners who I took particular delight in engaging in small acceleration contests. The car appeared completely stock except for a hood I modified with a bump to make room for the induction system.

I eventually sold the car to one of the Hayes Rotary technicians who had built the engine. A few days after the sale, the car was stolen and later recovered, with the engine removed, in Grants Pass, Oregon.

I've driven many high-performance vehicles but few that were as delightful as that crude machine with the engine that sounded like an Evinrude outboard.
posted by bz at 6:18 PM on January 15 [10 favorites]

Just curious, if it's so inefficient and technically difficult, why build it? What was the advantage?
posted by Mcable at 6:02 PM on January 15

The technical difficulties were solved (metallurgically) decades ago. There's nothing particularly difficult about them nowadays. The only really difficult part is manufacturing. It's easy to drill a big hole (read: cylinder) in a block of iron or aluminum. It's much more time-consuming and expensive to machine, finish, and coat something that's got a lot more complex a shape to it. Of course, once you do it (as for the 1.3 litre 13B-series of engines that lasted from 1984 until 2012), that's it, but you can't very easily change the dimensions of the engine to make, say, a 1.6 litre. And even then, you're talking about (potential) changes in 3 dimensions, not just making the cylinder longer or making it wider.

As for efficiency, well, the answer depends on how you define "efficient". Rotary engines are very inefficient in terms of something called brake specific fuel consumption - that is, how much power you get by combusting a unit fuel. That tends to make rotaries thirsty. It's not a problem that's easy to solve, and even then you can only usually do so incrementally. Rotary engines, however, are very efficient in terms of volumetric efficiency, power-per-engine-size and power-per-engine-weight. That's a fancy way of saying that you can make a relatively huge amount of power out of an engine that displaces a very small volume*, and it won't be very big, and it won't weigh very much. In the 80s, turbocharged 1.3 litre engines were making as much or more power than the very best 5.7 litre V8s that Detroit could produce. Back in the days of iron-block V8s, when lightweight aluminum engines were reserved for racing and exotics, their weight was also a huge advantage. Unfortunately, there have been massive advances in reciprocating engine tech in the last few years (VTEC, cheap energy means cheap aluminum, CAD driving superior design, etc) that have nearly nullified the advantages a rotary presents, while Mazda is the only manufacturer doing any sort of R&D into the rotary. They're getting outspent in development, and Mazda has always been a niche maker anyway.

* I won't argue with you about calculating the displacement of a rotary. You're wrong. So is the SCCA.
posted by TheNewWazoo at 6:20 PM on January 15 [7 favorites]

I loved the way my RX7 (3rd generation twin-turbo) drove, it was easy to modify, made tons of power (after swapping lots of parts), light weight, great handling... Unfortunately the thing got gas mileage in the high teens if I was being nice to it, it burned oil, and the motor threw a seal on the way home from work one day.

My suspicion was that Mazda ended up replacing a lot of the twin-turbo motors under warranty and decided to tone it down a lot for the next model. It's too bad too since a rotary always seemed like the way to make lots of usable power from a light weight engine.
posted by foodgeek at 6:32 PM on January 15

And the NSU Prinz predated the NSU Ro 80 by about 10 years.

Our neighbors bought a used rotary powered NSU Prinz in about 1961 or 62,
posted by buggzzee23 at 6:46 PM on January 15

foodgeek, the big thing, and this is what ruined the reputation of the rotary after the 79-85 RX-7 proved to be hugely reliable, was turbocharging. I've spoken with Rick Engman (if you know who he is, you know), and he's convinced that the heat buildup from turbocharging will always kill a rotary, which will otherwise run forever. When the RX-8 came around, there was no way in hell Mazda was going to run the risk of another line of cars with 60,000 mile engines*, so the entire question of turbocharging was a nonstarter.

People who owned them in the early 70s lost engines due to apex seals because the metallurgy wasn't quite there. Mazda got that mainly fixed by the time the 12A engine came. Then came the RX-7 in '79, and those things would (and do) run 250k+ miles at a time when Honda was only just starting to redefine the expected lifespan of an engine over 100k. Even the second-generation turbos were reasonably long-lived for their performance level (and when compared to the failure-prone 7M-GTE Supra and VG30ET 300ZX engines), but the third generation engines were a fiasco due to heat buildup, cooling system engineering mistakes, and wide dealer unfamiliarity with the monstrously complex control systems. Mazda lost their shirt on warranty repairs, and it was not unknown for owners to go through multiple engines before the warranty expired.

* I know the woman who owned what may be the longest-lived third-generation RX-7, and it died of water jacket failure at 105,000 miles. And she was the perfect owner.
posted by TheNewWazoo at 6:46 PM on January 15 [1 favorite]

Wankel Rotary Engine
posted by smoke at 6:47 PM on January 15

Goodnight old friend. I remember how heartbroken I was when the utterly fantastic 2ZZ engine was discontinued through lack of market and that they couldn't justify the investment needed to bring the engine up to Euro IV standards.

I thought the rotary would be next and I'm glad it lasted as long as it did.
posted by Talez at 6:50 PM on January 15

Hey, I'm with you foodgeek.
I loved my '93 3rd gen RX7 TT (silver on red leather) for 10 years.
"300 HP--NO PISTONS" I had engraved above the license plate, after a bit of tuning.

The incredible heat fried the rats nest of hoses under the turbo.

Anyway, I hope the current owner is enjoying at least half as much as I did.
posted by artdrectr at 6:51 PM on January 15

Also props to Mazda for the 3rd row in the Mazda 5 in the USA.
posted by humanfont at 6:51 PM on January 15

I lament the demise of the Wankel engine for the same reason I'm stuck in a permanent scowl as I'm searching for a more utilitarian car to replace the lovely Mazda Barbie dream roadster that is crushing the nerves in my neck. They don't make them like they used to, to firmly establish my age and state of crankiness, but that's really true.

I've had a love for the automorphous perverse throughout my life. My daily drivers have included a Saab Sonett and a set of Saab 95/96 models, ending up in my glorious decade of driving nothing but Citroens (Dyane, GSA, and DS21). I just love alternatives, and we just don't have many left. There used to be brilliant, peculiar designs out there, but these days, there's just vestigal remnants. The boxer in Subarus, the funky little engine at the back in a Smart. The occasional CVT. The stupid hybrid fad, which takes cars we've overloaded to the point of being monstrous tanks, even compacts, and overloads them more with absurdly complicated systems rather than just making them lighter. The monstrous panoply of expensive gadgets for drivers who should just be paying attention instead of waiting for their seat to vibrate because they've drifted out of lane.

My V4-powered Saabs had a freewheeling transmission, which basically worked like the freewheel on a bike. When you weren't pedaling (giving the engine gas), the transmission just let you coast. It was a silly evolutionary leftover on the V4 Saabs, since it had come about to deal with lubrication issues in the old 2-stroke Saabs, but man, it was fun. You just got used to using your engine like the chain on a roller coaster, and alternating between RRRRRR and and eerie silence. You shifted in that gap, so clutches lasted an eternity.

My Dyane, a 2CV derivative, was insanely, gorgeously engineered in its simplicity. Boxer twin. Aircooled. Machined to tolerances so precise it didn't need gaskets. No distributor--the plugs just fired on every stroke. No starter solenoid--you pulled a handle that pulled a cable that manually engaged the starter dog and switched on the starter. Inboard brakes, so wheels pivoted at their centers, which meant you didn't lose control in a blowout. The list was endless.

The DS and the GSA? Don't get me started.

Rust prevention is almost infinitely better now, but there's a real lifelessness to all the sameness out there. Cars are generally more reliable, but the metastasizing systems can't be touched by anyone but a mechanic blessed by the factory, and those heated self-adjusting ass-vibrating motorized memory seats cost you twelve hundred bucks when they stop being magical. The Wankel engine is, in some ways, a solution to a problem that no longer exists, but there's a beautiful simplicity and feel to it.

There are plenty of cars that are fast, fun, and even the crappiest cars handle better than some of the most advanced sports cars of the sixties, but there's almost no madness left. Unless you go for the most expensive and esoteric car out there, there's so little in the way of inspired, playful, experimentation out there.

Back in the day, when the Citroen DS was conceived, it was called the VGD, Voiture de Grand Diffusion--car for the mass market. It's almost inconceivable to dream of that sort of technology and creativity in a mainstream car now. The market has spoken, and what they want is beige. Sometimes it's cute beige, sometimes it's tragic beige, sometimes it's useful beige, and sometimes it's just beigey beige, but it's all just the same thing, year after year.

For us nerdy gearheads, alas, I suspect the end is near.
posted by sonascope at 6:51 PM on January 15 [10 favorites]

sonascope, I recommend you check out the upcoming Scion FR-S. It was reportedly designed to be a drivers' car in the RX-7's vein, and it has been certified by the TheNewWazoo School for Differently-Engined Vehicles, and I've found my Subaru to be wonderfully simple to work on.
posted by TheNewWazoo at 6:57 PM on January 15 [1 favorite]

The Wikipedia article notes various aviation applications of Wankel engines, specifically "They are increasingly being found in roles where their compact size and quiet operation is important, notably in drones, or UAVs.". A lighter, smaller profile engine with fewer moving parts seems tailor-made for airplanes, manned or not.
posted by Nelson at 7:00 PM on January 15

(I posted my previous comment because new comments kept appearing while I was responding to the previous ones that had appeared and I realized this was going to be a problem.)

Anyway, in the late 60s and early 70s, my grandfather's best friend owned the biggest Ford dealership here in Albuquerque and decided to invest in a Mazda dealership with a partner in 1971-1972, when Mazda started its US operations.

I don't know if my dad knew much, if anything, about Mazdas or the Wankel engines before this, or if he first learned of them through my grandfather's friend. He might well have already known something, because Dad was very interested in cars and racing, had been a regional champion drag racer. (He was also a bit of a notorious teenage delinquent, and his friends have a great story they tell about him actually stealing the transmission from a car parked in someone's driveway in the middle of the night. Racing's a little bit in our family and he have numerous connections to it—our extended family knows the Unsers and Dad was good friends in high school with team owner Rick Galles.)

So, in 1972, my dad was 28, I was nine, and he bought his first new automobile: a 1972 Mazda RX-2, orange. A couple of years later my parents bought a 1974 RX-4 station wagon when my sister was born.

I learned to drive in that RX-2. At about twelve or thirteen. Dad was a big believer in both defensive driving, and knowing how to handle a car in all conditions...which also requires that you be aware of its performance profile. He took me out one snowy day when I was about 13 to teach me to control an oversteer. After doing a bunch of doughnuts first, of course.

On another snowy day, when I was fourteen and my parents were out of town for a couple of days when my sister went to a doctor's appointment (for our genetic disease), I stole that car, picked up a friend, and for some stupid teenage reason, did doughtnuts for ten minutes in the empty parking lot of the supermarket on the main highway through town. Until the cop came. He gave me a ticket for driving without a license, but not reckless driving. I told him my parents were out-of-town and I was staying alone and there was no one to come get me and the car, so the cop told me that I couldn't drive the car home but that "what happened after he drove away he wouldn't know about". Then, a couple of weeks later when my dad and I went to the courthouse to see the traffic judge, the judge was under the impression that I had been stopped while Dad was teaching me to drive in town, and so he told my dad to teach me out on a country road somewhere and dismissed the ticket. Dad didn't dispel his misconception, which might have been a mistake. This wouldn't be the last time I got in trouble with the police in that car.

I was always partial to the RX-2 over the RX-3 because it was lighter, but with the same engine. That car was fast, deceptively fast. And it handled quite well, too. I learned to do a lot of interesting things in that car.

My first car was a 1975 Mustang II during my junior year of high school, which really disappointed me. Both the car and my junior year, most of which I didn't bother to attend. I also didn't keep the job I was supposed to use to pay my parents for the car they bought me, so they took it from me and sold it.

Then, that summer, while my cousin from out-of-state was visiting, I borrowed that RX-2 from my dad one afternoon for a "go there and straight back" trip to nominally help out a friend with his stalled car. But on the way home, I saw some girls coming the other way that I knew and made an illegal U-turn to catch up to them. When I saw the cop pull into traffic, I panicked and took a right and accelerated. When the cop made the right, I was already five blocks ahead of him in a residential neighborhood and going about 70MPH.

I did some pretty great driving that day. In fact, I outran the police cars that were chasing me. On the other hand, I eventually discovered that there wasn't anything I could do about the ones who blocked the road in front of me. (A dirt road alongside the railroad tracks by that point, as it happened.)

The police arrested both me and my cousin. He was a year younger, only fifteen. I felt bad and knew I had screwed up—when I stopped the car, I was immediately remorseful. However, they handcuffed me and then handcuffed my cousin, which baffled me. I asked why they were arresting him, and a cop said, "Because anyone in a car when a crime is committed is an accessory". I responded, "That's stupid! He had no idea I was going to do this and I was going over seventy down city streets. What did you expect him to do, grab the steering wheel? This isn't his fault!"

My cousin, a little more pragmatic and worldly than me, perhaps, told me to "shut up".

As my mom was at, apparently, "jazzersize", and I had been driving my dad's car, he actually had to walk to where she was to get her car before he could come to the police station after they called him. Mom later told me that I was very lucky on that count, as that gave him time to cool down.

My cousin and I were in this small-town holding cell right next to the squad room, so I heard everything when Dad finally walked into the station. He sat down and the cop started telling him what happened. And then the officer said, "Well, Mr. E, your son was lucky today. It was very dangerous; he almost rolled the car."

This is what I heard my dad say to the police officer: "I know my son, and I know that car...and he didn't almost roll that car."

So that's why I went my senior year without a driver's license or a car, which was a really unpleasant thing for a teenager in a small southwestern town in 1981-1982.

Although, to be honest, that year I did end up stealing that RX-2 fairly frequently in the middle of the night while my parents were asleep to go meet friends. Or, hell, just drive around. I had a makeshift rally course I'd sort of stumbled upon that I liked to practice on. I'd discovered that I could reach up under and behind the dash and unscrew the odometer cable so that Dad wouldn't know I'd driven the car. Over the subsequent decades, I always sort of worried about maybe having to confess this to him someday, but he died a few years ago without ever knowing so that worked out okay.

I was arrested while driving that car one more time a couple of years after high school, but that's another story. By that time, I'd inherited the car, which I'd coveted for a long time.

Before that, I'd actually owned two other Mazda rotaries—I'd been given that RX-4 station wagon when I graduated high school, but I stupidly let the oil run dry (as others have mentioned, because of the design, Wankels consumed a small amount of oil) and ruined the engine. Then I bought another RX-4, which turned out to be a disaster. Definitely in that case the apex seals were shot. I actually just abandoned that car in the parking lot of the university I had been (not) attending in Texas. So I ended up with the RX-2, finally.

I traded that in for a new car, a Mazda, naturally, in 1986. But the car I bought was a 323 (which, was a surprisingly sprightly little car—I literally drove that over a mountain range on roads that had forest service signs saying that the roads were too rough to be driven on even by most 4x4s). Later, I bought an MX-6. So, I've owned a bunch of Mazdas.

The last generation of RX-7s were the epitome of the RX-7 and Mazda's hard-core racing aesthetic. It was famously uncompromising in its handling. And the body was truly beautiful, a work of art. In 1999, when I came into a bunch of dotcom money, I hired a guy to scour the country for the best condition 1994 RX-7 he could find. In the end, however, I bought a BMW 840ci, which was a whole 'nother kind of driving experience, let me tell you.

The RX-8 was an attempt to find a compromise between the pure sports car of the RX-7, which was too expensive and just didn't appeal to a more casual market, and something like the incredibly successful Miata, which didn't really perform that well, but was fun.

It had no appeal to me. So, for me, the Mazda rotary has been dead for a while.

I know, because people talked to me about this just a couple of years ago when I was there, that I made quite an impression on my peers in high school with that RX-2, even though it wasn't at that time even my car. For a while, I could count on people underestimating it and racing them and embarrassing them. Later, people just liked to ride with me and see what it could do. I did some really crazy and stupid stuff. You know, it's a bad idea to go over 90MPH on a dirt farm road. But, hey, those guys we were chasing had insulted a friend of ours and left the party and we couldn't just let them run out and get away with it, could we?

I still dream about that car. I mean, seriously, I dream about driving that car. One of my biggest regrets is that I never pursued any sort of auto racing. I had the performance manual for that RX-2, with which I could have modified the engine for track racing after I'd bought another car. There's not a year that goes by that I don't regret just trading it in for the lousy thousand dollars or whatever I got for it.

If you look at YouTube, you'll find that, apparently, Australia is where all RX-2s and RX-3s retired to and even today, live on forever. Watching those videos quite literally brought tears to my eyes.
posted by Ivan Fyodorovich at 7:25 PM on January 15 [10 favorites]

"but I cannot read "Wankel rotary engine" without hearing it in the voice of John Cleese."

Except when I hear him say it it's Wanker.

I think williampratt was referring to this particular Cleese/Python gem.
posted by Strange Interlude at 7:39 PM on January 15

We've gone this far without mentioning the rotary motorcycle???

(Drove an '85 RX-7 thru 1998, which it caught fire because of a dealer fuck up, though the seals were going at about 150k miles. When I first got it, I occasionally forgot to shift.)
posted by ambient2 at 7:45 PM on January 15

When the RX-8 came around, there was no way in hell Mazda was going to run the risk of another line of cars with 60,000 mile engines*

Sadly, the 8 seems to have its own longevity issues. The first iteration of the 13B-MSP eliminated the center oil injector, so there have been lots and lots of apex seal failures with under 50,000 miles. Mazda now warranties the rotor core for 96k miles and has a facility in Virginia to pump out reman engines.

The Series II (09+) restored the 3rd OMP injector, so here's hoping that the longevity comes back. But the damage to the reputation was already done. Even after the dealers clear out their inventory, fewer than 5,000 SIIs will have been sold in the US since 2009. Unsubstantiated internet rumors claimed that Mazda spent as much on the refresh as they did on the original model development.

It had no appeal to me. So, for me, the Mazda rotary has been dead for a while.

Have you driven one? So many people have discounted the 8 out of lament for the FD without even the courtesy of a test drive.
posted by hwyengr at 7:58 PM on January 15

Back in my younger days I had a FB who had an RX-7. Since we'd reached the point in our relationship of having tried all the more common positions, and personally having had success with a previous FB Doing It in the back seat of a VW Beetle (while recovering from a broken back, so sometimes hormones do drive brains), I suggested we try it in the RX-7. I'll never forget the RX-7, or the feeling of the gearshift in places gearshifts have no business being felt.
posted by Runes at 8:11 PM on January 15

(Runes, that comment really confused me. "FB" is the dork term for the second series of the first-generation RX-7 [81-85 12A].)
posted by TheNewWazoo at 8:15 PM on January 15

My father owned one of the mid-series gen 2 RX-7s. It wasn't a screamer, but it was a really fun car to drive. It was a real dog at low RPMs, but once you hit about 20 mph it was as sporty as you'd like. I still drool thinking about the 3rd gen RX-7s: I still think it's the most beautiful body design that any Japanese car manufacturer has ever managed.

Yeah, the RX-7'd never compete with a cheap E30 that you dumped a ten grand of upgrades into, but that wasn't the point. The RX-7 had a nice enough ride and interior that you could pick up a date in it, but it was also hot enough that you could rip into traffic coming down those too-short on-ramps in downtown Lynchburg. Maybe get your date's heart rate up a bit without looking like you were hot-dogging it or showing off.

A coworker of mine owns an RX-8 and, while it's fun and all, it's eaten two (manual) transmissions and just doesn't have the same raw feel as the old RXs. The doors are a neat touch, though.

So my dad drives his RX-7 to work most days from spring to fall and that old beast has survived about 160k miles with no complaints. It had one of the heater control sliders fail and, in my teenage years, I hit a deer and mailbox with it. I thought my dad was going to kill me, but he handled it surprisingly well. It was a good lesson for me.

Anyway, I think those were the only times it was in the shop. At Thanksgiving, my dad has decided to rebuild the engine to fix a hot start problem that it developed during the summer. Apparently the point seals have started to weep, but the car is still a hoot to drive and it keeps him entertained. Maybe when he decides to give it up it can come live in my garage. I wouldn't mind having it for those lazy weekend spins out along the Blue Ridge Parkway. Put windows down, open up the sunroof, and listen to the whorrr of the rotors as you step on it coming out of a corner...


,
posted by introp at 8:29 PM on January 15

"I'll never forget the RX-7, or the feeling of the gearshift in places gearshifts have no business being felt."

That's interesting. I had a sometime-girlfriend in high-school who was quite fascinated with the shifter on the RX-2. And by "fascinated", I mean...well. Is it because Mazdas go "hummmmm"?

This is pretty much a complete non-sequitor, but the last I heard she ended up being the cellmate of a notorious psycho-killer. I'm pretty sure it wasn't my fault, but you never know.
posted by Ivan Fyodorovich at 8:29 PM on January 15 [1 favorite]

Have you driven one? So many people have discounted the 8 out of lament for the FD without even the courtesy of a test drive.

There are those of us who discounted the 8 after driving it. I truly hoped that I could buy one to rescue me from Subaruville where I ended up after blowing up my RX7, but after driving a few of them it was clear that I needed to look elsewhere for its replacement.
posted by foodgeek at 8:33 PM on January 15

It always seemed to me, at least in cars, that the WRE was a very clever technical solution desperately searching for a problem that needed to be fixed.

The one thing it was truly superb at -- power to volume -- is not a problem for any but the tiniest cars. The other thing it was good at -- power to weight -- Honda beat with VTEC, and the WRE never really did regain that advantage.

So, WREs in cars are very small for their power, get lousy mileage, and weigh just as much if not more than a conventional four cycle engine. They still take up much less space, but this simply isn't an issue in the vast majority of cars.

I've always wondered why they didn't become big in aviation, where power-to-volume/weight are vastly more important than they are in cars, but in conventional planes, they simply didn't. I suspect it was either reliability or confidence - that is, nobody was willing to bet on the reliability because of lack of evidence.

Aero engines tend to be a weird combo of very conservative on one side, and very clever on the other. Current engines, esp. turbines, are very clever, but they are a design evolved over seventy+ years now, very carefully evolved. Cheaper engines tend to be very simple, because the three most important things in an engine meant for single engine installation are reliability, and power-to-weight/volume/fuel aren't nearly as important as making sure the damn thing works from takeoff to landing.
posted by eriko at 8:44 PM on January 15 [1 favorite]

I have rarely felt such thrilling exhiliration for a driver as with watching Johnny Hebert smile underneath that big helmet of his. With the links concerning alternative fuel mehods, something tells me is this not the last we'll be seeing of the Wenkel.
posted by Meatafoecure at 8:45 PM on January 15

The RX-8 was competing with family sedans that were making an honest 40 horsepower more when it was introduced, while doing 28 mpg on the highway, and it's only gotten worse since. I directly shopped the RX-8 with the WRX, and you just can't ignore 16/22. Ouch.

Unfortunately, Mazda has said (sorry, no cite) that they're trying to pair the rotary with other engine tech like hybrid technology, but I don't predict that to be a winning combination. IMO hydrogen-powered cars are stillborn, too.

eriko, I'll take a stab at the lack of aviation rotaries. I suspect it's due to the fact that only Mazda builds them, and they're not interested in getting them certificated. Rotaries have some very significant advantages beyond just size/power/weight that aren't worth getting into here, but the ROI is probably not enough to elevate them over turbines. They're really popular in experimental craft and in RC planes, fwiw.
posted by TheNewWazoo at 8:50 PM on January 15

My friend had an RX-7 that was just a blast to drive and tool around in on the back roads around his army base in the south of England. Sad to see these die off, the choice for interesting cars just got a bit smaller.

Also, this far in and no zoom, zoom jokes?
posted by arcticseal at 9:09 PM on January 15

Well, you can ignore the gas mileage. But my car was sitting on the lot for a year so the dealer was very interested in getting it gone, and Mazda had super deep rebates going, so I can buy a lot of gas before getting back up to sticker price.

But mine's also the low-end Sport model. No leather, no traction control, no stability control. Just me and my right foot. And the quart of 5w-30 in the trunk.

Also, this far in and no zoom, zoom jokes?
Funny enough, my original post title was a zoom-zoom joke.
posted by hwyengr at 9:15 PM on January 15

*smacks forehead*
posted by arcticseal at 9:21 PM on January 15

this is what a rotary sounds like

like a cross between a chainsaw and a dirtbike.

and yes, the relentless surge toward efficiency will continue to kill anything interesting about driving. for those who don't want our cars to be ipods, at any rate. most input functions are communicated via wiring and not actual mechanical linkages. and that really removes that direct connection we as gearheads had to our vehicles. i may eventually buy a prius or something ultra-efficient. but i'll always have room for something old, noisy, and mechanical in the garage. it just won't be an RX-7 (my latest fascination is the Datsun 510/bluebird. and people DO put rotaries in these.. but no, thanks).
posted by ninjew at 10:07 PM on January 15

To this day Mazda remains the only Japanese carmaker to win the 24 Hours of Le Mans, a feat they accomplished in 1991 with the 787B, powered by a four-rotor engine. Just listening to that beast is enough to make the heart melt of any rotary fanatic. After Mazda's victory rotary engines were forever banned from Le Mans.
posted by Kraftmatic Adjustable Cheese at 10:41 PM on January 15

(Hmm, I probably should have read the whole post before commenting. But listen to that car!)
posted by Kraftmatic Adjustable Cheese at 10:46 PM on January 15

The DS and the GSA? Don't get me started.

The terrifying thought is that Citroën also built and sold, then abandoned, the GS Birotor, a GSA with a Wankel engine. Imagine: Citroën hydropneumatics and a then-novel engine, combined with that legendary early-70s French car reliability, and no after sales support whatsoever. That is my idea of automobile hell.
posted by Skeptic at 10:56 PM on January 15

The Wankel is compact and effiecient and certainly has a future even if as usual its taking a production break. I imported lots of the FD3S RX7's from Japan and they tended to come in two versions (A) Just had a rebuild (B) Needed a rebuild. Enthusiasts that bought them didnt really mind getting the spanners out though. The RX-8 was car of the year when it came out and Ive seen plenty with 100+K miles, but to an average consumer the constantly varying sound of the engine does not inspire confidence. Hence resale value is tragic which would be the main reason Mazda are letting it go.
posted by duffers5000 at 12:28 AM on January 16

I have mixed feelings about the Wankel engine. On one hand I appreciate its cleverness and like the retro-futurism it evokes. On the other hand, it was, as eriko points out, a solution in need of a problem, with quite fundamental energy efficiency flaws. Above all, in engineering school, the professor in charge of my Thermal Engines course was a Wankel fanatic, and spent half the course filling our heads with stuff of now quite marginal usefulness, like epitrochoidal envelopes. Nobody is giving me back that year of my life...
posted by Skeptic at 12:55 AM on January 16

Wankels are still inherently more efficient

Not in terms of energy efficiency. The fundamental flaw of the Wankel engine is the very elongated shape of the combustion chamber at ignition. This has several drawbacks (it's more difficult to achieve an homogeneous combustion, for instance), but the most significant is a large surface of the combustion surface. Large surface -> large heat losses -> poor fuel efficiency. You can't engineer that flaw out of the Wankel engine.
posted by Skeptic at 1:16 AM on January 16

Large surface -> large heat losses -> poor fuel efficiency. You can't engineer that flaw out of the Wankel engine.

Flaw two -- the heating happens on one side only, rather than the heat-and-cool cycle of a piston engine, one part of the housing is always heated, the rest aren't. This makes shaping the housing tricky, and makes sealing even harder.

Indeed, you can't have tight tolerances in a wankel. Almost all of them are made with steel rotors and aluminum housings. This means the housing expands more than the rotor. Good thing -- basically makes the engine impossible to sieze. Bad thing -- basically makes the engine impossible to seal. Someone joked that a WRE is basically two moving part (rotor, driveshaft), two stationary parts (the housing and cover), one firing part (the spark plug) and 150 parts trying to seal the combustion chamber.

And, for all that, it still has to burn oil to keep the apex seals functioning.

They're really popular in experimental craft and in RC planes, fwiw.

At least they're being looked at -- and in RC, where space is often the major constraint, it's not a surprise at all. You're right about other issues -- the biggest being that they're best at constant high revs, which means you're going to need a gear reduction unit to drive a prop, and if you need a gear reduction unit, you have to count the weight, size and cost when comparing to a piston engine that you can bolt the prop directly to the drive shaft.

Seems that, without the valve sealing problem and with the heat on one side, it would be trivial to get rid of carb icing, which would be a clear win.

I do agree with posters above that the WRE hasn't seen a fraction of the engineering work that the modern diesel and gas piston engines have. But, right now, I'll bet most are thinking "But, we're really good at these, and more importantly, the focus has changed to even more fuel efficiency and even less emissions." They're not going to switch unless there's an engine that shows at least a path to significantly improved fuel economy and emissions while retaining similar power outputs.

Given that it's easy to get 100hp/liter* displacement, you can get 100hp in a very small engine, or 100hp out of a slightly larger engine that's very fuel efficient**, or get wide torque bands***, or more power**** or even MORE POWER†

It's hard to match a technology that gives you such a range of options. You can build high torque, high power, high efficiency, trade them off as needed, and over the years, the petrol and diesel engines have only gotten better at all three.

That's why they rule the roost. The same basic tech that runs the Honda Civic runs the F150 truck, the Cessna 175, the Bugatti Veryon, and the Emma Mærsk class†† of container ships.

It is really, really hard to find a tech that can challenge that. The closest we've seen is turbine engines, but the only real realms where we see both turbine and piston engines is propeller drive airplanes and shipping, though turbines only appear in high speed uses.

The WRE might be able to match a considerable amount of that range, given enough engineering work. But to pay off, it has to match a considerable amount of that range in a significantly better fashion that the current crop of reciprocating††† engines.

That's a tall order -- and I'm not surprised that there isn't anyone really willing to bet on the WRE meeting it.


*Hell, you can get that out of a Volvo nowadays - C30, T5 engine, Polestar ECU upgrade (Note, that's a dealer upgrade.) 250HP in that little thing? Hot Hatchback FTW!

** Honda L13A iDSI -- 1.3L, 93HP.

*** Tweaked Honda K20A 2.0L -- 300 HP, or 150HP/liter

**** Stock Volvo B5254T7 has 236ft-lbs of torque from 1500 to 5000RPM. I actually think this comes on too fast for a FWD car.

† The engine on the current SSC Aero -- a V8, has 6.3L displacement, producing 1287bhp -- over 200HP/liter. Yes, this

†† Meet the Wärtsilä-Sulzer RTA96-C: Displacement -- 25,480L. Not cc, liters. Power 109,800bhp @100rpm. Torque? 5.6 *million* ft.-lbs.

††† Finally, after 10 paragraphs and six footnotes, I remember that damn word.
posted by eriko at 5:48 AM on January 16 [1 favorite]

A friend in college had a 1974 Ferrari Dino kit car built on a Mazda frame, with the rotary engine. Obviously, the Wankel sounds like a go-Kart compared to the roar of a real Ferrari, but college girls in Indiana don't know that. Girls would literally wave us down on the street. I'd get out, hang out on the curb while my buddy took girl 1 for a ride in the car, then he'd give girl 2 a ride, while I hung out chatting up Girl 1.

Then there was the time he was giving me a ride to the airport to go home for Christmas, and the car wouldn't start due to a sticking solonoid (IIRC). We took a meat hook from the frat house kitchen and used it to short out the solenoid and start the car. Good times...
posted by COD at 6:21 AM on January 16

I am shocked, shocked, to read a posting about Wankel rotary engines with no mention of the NSU Ro80, one of which Erik Spiekermann owns.
posted by joeclark at 6:41 AM on January 16

My dad spent six of his 30+ years in long-range powerplant R&D for one of the Big 3 trying to figure out how to put a rotary engine into an American production car. They never did figure it out, and they worked fairly closely with Mazda. IIRC, one of the problems they ran into was the size of the engine -- the Wankel was so much smaller than other engines with the same power that the geometry of the engine compartment and powertrain was very different, and it really wasn't feasible to just drop a WRE into an existing model. They also were concerned about being able to build the engine in the quantities needed for an American production vehicle.
posted by jlkr at 6:57 AM on January 16 [1 favorite]

The terrifying thought is that Citroën also built and sold, then abandoned, the GS Birotor, a GSA with a Wankel engine. Imagine: Citroën hydropneumatics and a then-novel engine, combined with that legendary early-70s French car reliability, and no after sales support whatsoever. That is my idea of automobile hell.

The funny thing for me is that I always heard some of these warnings about French reliability, but in 150K miles of driving thirty year-old Citroëns as my everyday transportation, I never once got left on the side of the road. People speak with great authority (from the outside) about the hydropneumatic systems, thinking that they're somehow the problem with Citroëns, but unless you actively do stupid things (i.e. Dextron in the hydraulics to save a few pennies), the hydraulics aren't a problem.

Like all sixties and seventies cars, they rust like crazy, but if you do basic maintenance, their reliability is on a par with the output of any contemporary carmaker. In the end, my Citroëns went like this—the feds confiscated my illegally imported diplomatic corps GSA, my Dyane's chassis finally rusted through at 35 years on the road, and my DS needed a clutch, which is a job beyond my skills and available tools and hardware (25 hours labor for a trained mechanic), though that happened at 360 thousand miles (of which I'd added 80K), so it wasn't really a persistent problem.

The problem with the Birotor (and its lesser-known predecessor, the M35) wasn't the platform—it was that materials engineering in the late sixties just couldn't produce workable tip seals for a Wankel engine, and Comotor had some engineering problems that they never beat.
posted by sonascope at 7:14 AM on January 16

Citroëns as my everyday transportation, I never once got left on the side of the road.

Citroëns had a pretty good reputation for reliability from what I can tell -- the were not pre-1992 Mercedes level, but they were certainly vastly ahead of, say, Alfa-Romeo.

French cars as a whole in the US are tagged by the failure of the Renault LeCar (which was the Renault 5 in Europe) and the Renault Alliance, a joint project with AMC. Both (but esp. the latter) were plagued with quality and reliability issues. The Chrysler buyout of AMC ended that project.
posted by eriko at 8:47 AM on January 16

If you like rotary engines and weird old compact pickups, you'll love the REPU.
posted by box at 8:48 AM on January 16

ninjew, a Dazda was my dream car for a couple of years of my youth. All the awesomeness of the Datsun 510/1600 made even better with the cheap, lightweight power of a rotary. Pretty much the perfect rally car in the early 80's under the oddball regulations in Australia at the time. If I could afford someone to take care of it I'd be building one right now.
posted by N-stoff at 9:15 AM on January 16

Ah man...I remember writing a note to myself at some point to look into an RX-7 or RX-8 at some point. They're beautiful little cars, and that hum is so enticing. I didn't know anything about the engines, I just saw them a lot as project/modding cars, with extra fins and lowered shocks, and thought they looked cool. I think I took them off my list of potential cars when I found that they were manual-shifters. But I love their look and sound. Too bad they're being discontinued! I've really enjoyed reading the stories here.
posted by limeonaire at 9:57 AM on January 16

My RX-2, my friends called the "Mazdarati."
posted by bz at 10:04 AM on January 16

Why is the Wankel not used for hybrid gas-electrics? Would it not be as efficient as the piston-powered engines that are being used?
posted by davidpriest.ca at 10:50 AM on January 16

"I just saw them a lot as project/modding cars, with extra fins and lowered shocks, and thought they looked cool. I think I took them off my list of potential cars when I found that they were manual-shifters. But I love their look and sound."

No offense intended whatosever, but I found these three sentences deeply disturbing. Any car I really care about driving must have a manual transmission.
posted by Ivan Fyodorovich at 10:56 AM on January 16 [1 favorite]

"No offense intended whatosever, but I found these three sentences deeply disturbing. Any car I really care about driving must have a manual transmission."

I'd be curious to know if an afternoon with the Porsche PDK might change your mind. Did mine.
posted by bz at 2:50 PM on January 16 [1 favorite]

Interestingly Mazda sold a General Motors Holden Kingswood fitted with a 13b in Japan.
posted by onya at 6:18 AM on January 17

> It's that you can't really make the displacement much smaller to get more efficiency out of it
> the way that you can with pistons.

You can do half of that, anyway--make it smaller. There is actually a Wankel model aircraft engine that is listed at 4.97 cc displacement. It looks like this. But making it small doesn't seem to have helped with the efficiency. This model aircraft hobbyist reports "It burns fuel so inefficiently that I have decided it is strictly a novelty engine and I display mine in a glass case."
posted by jfuller at 9:43 AM on January 17