So the problems are not solvable. I was involved in a Wankel program through GM about 30 years ago. Just when it was ready to launch ,they killed it. Word was the seal was too short lived. and it was unworkable But since that time I figured that would have been solved.
The Wankel engine IS an inter… oh, wait, you got it.
But, while the Wankel was heavily advertised as “rotary” and therefore smoother than piston engines, this is pretty misleading. The rounded triangular rotor doesn’t just turn, it also travels up and down. And it’s much bigger and heavier than a piston. Moreover, piston engines can cancel the piston momentums pretty neatly - for example, Subaru engines often have 4 horizontal cylinders arranged in two pairs that are almost directly facing each other, and the piston motions in each pair are both going outward together then both going inward together. The center of gravity of pairs of pistons doesn’t reciprocate. By far the heaviest moving part in a piston engine, the crankshaft, is rotary, and rotates at a pretty constant speed (on a short time scale).
The rotary engine is a seductive concept, but its geometry causes inherent problems. The sealing is MUCH more difficult than with a cylindrical piston. People have been grappling (pretty much unsuccessfully) with this sealing problem since James Watt tried to make a rotary steam engine. See http://www.dself.dsl.pipex.com/MUSEUM/POWER/rotaryengines/rotaryeng.htm for the epic story.
I understand that another inherent problem is that the combustion space is long and thin, and therefore suffers greater heat losses that reduce efficiency.
The rotary engine typically had paired rotors as well, which accomplished the same cancellation. That engine had a TOTAL of 3 moving parts, including both rotors. I spent a lot of time driving mine, and I can say without reservation that it was the smoothest running engine I’ve ever felt (though I will admit that I’ve never been in a 12 cylinder Jaguar).
The vibration caused by a piston slamming against the end of its travel, twice for each rotation, is inherently worse than a rotor that never reverses direction, but gets a push in the same direction not only once each revolution, but several times, even tho the push is still an explosion.
I’m sure sophisticated engine design can minimize or counterbalance serious vibration, but certainly a rotary engine has a head start in this department.
I had an RX-8 for three years. The oil consumption was never a problem - it would use maybe a litre a month, if that, and it’s standard oil, not expensive stuff.
The problem was the fuel consumption - I was doing well if I got 20mpg out of it (that’s UK gallons), and by the time I got rid of it, petrol had broken £1 per litre. (That’s US$7.60 per gallon, give or take).
Lovely smooth high-revving engine and a lot of fun to drive, though. No torque at the bottom end but it would rev for ever (well, until the limiter kicked in around 10,000rpm).
A Wankel would be a good powerplant for a motorcycle-were they ever made?
IIRC, that was the original intended purpose for the engine. I don’t recall seeing any actually made, other than prototypes.
I don’t know…maybe they also sold my coworker some magic beans.
>The rotary engine typically had paired rotors as well, which accomplished the same cancellation.
No, the paired rotors were not traveling along the same line as they moved up and down. They were both on the same shaft, or more accurately were orbiting around the same shaft. Therefore there was an angular momentum vector crossing the shaft perpendicularly midway between the two rotors and changing sign twice for every oscillation of the rotors. Pistons can come much closer to cancelling each other because they can be spaced closely along the crankshaft, and they weigh less than Wankel rotors too.
Your car may have run very smoothly, and for all I know they may have made the engine run with relatively little vibration somehow, but it can’t be because the engine is only rotary.
>The vibration caused by a piston slamming against the end of its travel…
Slamming? The piston moves in something very close to sinusoidal motion, with all the derivatives continuous, nothing discontinuous. Well, there can be some slapping of the skirts, but not much. And the rings might move back and forth in their grooves, I guess. But slamming? Against what?
If you spin a flywheel in free space, points on that flywheel are moving along any vector you like (except the axial one) sinusoidally. It doesn’t have to be discontinuous in any way. If you believe space is linear, you sort of have to believe you can resolve vectors and analyze dimensions independently and still have the same results.
>That engine had a TOTAL of 3 moving parts, including both rotors.
Does a small number of parts suggest it should work smoothly? Jackhammers and the dangerous old gas-driven soil tampers (the big heavy things that jump up and down on a metal foot while you try to hold on and guide it and not get a steel punch in the jaw) - these things only had ONE moving part, or only one sizeable one, anyway.
IIRC, American Motors originally designed the Pacer
http://www.channel4.com/4car/media/features/2005/crap-cars/03-large/1975-amc-pacer.jpg
To be powered by the GM Wankel, but switched to a straight six when GM pulled the plug on rotary powerplants.
Against the linkage. While some parts (crankshaft) may have continuous rotary motion, the pistons themselves are straight-line. They come to a sudden halt, reverse direction, halt again, reverse again. Each time they halt, they interact with other parts that do not halt, but resist their motion. And an explosion is behind all this for each cycle. It’s not a rockabye baby-gentle action, and the wear and tear on these kind of components is considerably greater than a rotary, electric motor, for example.
If you don’t believe me, I suggest looking into some basic mechanical engineering concepts.
What about the Wankel engine causes it to rev significantly higher than a standard opposed cylinder powerplant? Less moving parts?
Inertia/momentum.
Pistons have to speed up, slow down, stop speed up in the opposite direction, slow down stop, repeat ad infinitum. Its hard to get something that constantly changes direction to get to high speed
A rotary’s angular momentum is continuous…easier to rev.
Furthermore, a rotary has no valvetrain other than the rotor itself uncovering the ports: also no restrictive poppet valves for glasses to flow past, nor valve spring resistance to overcome.
I have spent lots of time in V-12 Jags and it is no comparison, the rotary is smoother by an order of magnitude. Or so it seems to my calibrated Mark 1 mod 1 butt.
Give it up dude. Look up why you don’t see 4 cylinder engines that displace over 2.5 liters. Or why Mitsubishi developed balance shafts. (Hint: It isn’t because a piston engine is smooth) The piston has to reverse direction twice every revolution. Lots and lots of vibrations.
Suzuki had the RE5
I’ve participated in a few engine builds & rebuilds for both rotary & piston engines so I thought I’d share a few photos for anyone who is curious.
These engines are tiny compared to larger piston engines and as others have said, there aren’t as many moving parts.
It’s late and I’d love to say more but for tonight I’ll just post the photos.
This is the motor from a 13B (93 RX-7) from the flywheel forward: the housings, rotors, eccentric shaft, oil pan, seals and other miscellaneous parts.
One of the rotors.
Motor and trans hoisted out of the car.
Me starting to disassemble the motor.
The beautiful car this (bad) motor came out of.
We don’t discuss flooded Wankels in polite company. 
Also the Norton Commander