I can't argue with a single thing he said, but for a power to weight ratio, the rotary can't be beat by pistons.
For an insane story about how it was conceived, you can't beat the Wankel period.

except for the fact it isn't quite dead:

http://blog.caranddriver.com/new-spin-mazda-files-patent-for-new-gen-rotary-engine-heres-what-it-tells-us/

So, what was the advantage of this engine type?

Ill take a stab. Engines ran forever(much longer then others). More reliable. Less repairs. Plus back in the day when they were popular the gas mileage and emissions were most likely on par with the cars that were out at that time. Back then mileage and emissions weren't as important as they are today.

The main advantage, power to weight...this one is HUGE for performance vehicles. Also in it's favor; reduced vibration (over piston engines), only two moving parts, no valve train, and the fact that it's 'exotic'.

EDIT: Cons: terrible mileage, bad emissions, loud (it's can't handle much back pressure, so you can't put on much of a muffler, and the unburnt fuel 'pops' loudly as it leaves the exhaust), hard to replace Teflon seals requiring a full teardown to replace, hard to find a mechanic that can work on them (especially if you need machining done), hard to find period (they're quite 'rare' compared to piston engines)....I'm sure there's more I'm forgetting or don't know.

***update -- I was wrong about P-47 having a rotary engine, confused *radial* with rotary. Other than noting that mistake here, I'll leave my original comment unedited below (in which I draw erroneous conclusions based on that brain fart):

@eric3579 and @newtboy -

I was also quite interested in the "advantages" question. My grandfather was an armorer on P-47 "Thunderbolt" aircraft in WW2, and I knew that rotary engines were used in those.

Both of your answers tie in to the strengths of P-47s during the war. They were considered very reliable and resistant to damage (sorta like a WW2-era A-10; they could take a beating and make it back home). And of course, in internal combustion powered aircraft, power to weight ratio is even more important than in automobiles.

So, I'm sure that some of those strengths were at least partially due to the use of a radial engine. Not entirely, because other things in the design played a big role also -- like the fact that the P-47 engine was air cooled, so it didn't need a radiator system. As I understand it, comparatively light damage to a liquid-cooled aircraft like a P-51 that happened to damage the cooling system could disable or force them down for repairs... Not to knock the amazing piece of engineering that the Mustang was, but for sheer ability to take a beating and stay in the air, the Thunderbolt may have been the best US fighter in the war.

Whoops -- I screwed up.

P-47 had a *radial* engine (with pistons), but not a *rotary* engine.

So I guess I was reading too much into the advantages of rotary engine coinciding with the advantages of the P-47.

I'll leave my post above unedited and own my brain-fart, but I hereby own up to being all wet and wrong about it!

Two different types of engine are both called "rotary" and both have been used on airplanes to confuse people.

https://en.wikipedia.org/wiki/Rotary_engine

https://en.wikipedia.org/wiki/Pistonless_rotary_engine

Also a rotary engine (most WWI warplanes) can look fairly similar to a radial (some WWII warplanes) unless its running.

The principle of the wankel engine is not dead. At this time other principles have been developed better but it can come back with better materials and design.

It would be awesome if there was a way to bring back real old style rotary engines, I love visible moving parts, very steampunk.

Thanks for that, makes me feel better about getting them confused since the terminology is semi-fluid.

Seeing the disassembled Wankel engine in the video should have clued me in that that was NOT what was used in the P-47, which had lots of big cylinders for pistons radiating around a central point, hence the "radial" designation.

It (the video) was very helpful for figuring out how the chambers and path of the parts work in comparison to a piston engine, which is quite interesting even for someone like me who really only understands the rudiments of either design. Live and learn!

I once worked in tech support with someone who when his car started overheating, tried turning it off and back on again.

The rest of us found great humor in him trying to "reboot" his car.

You do know cars are run by computers these days?

I'm assuming this is a joke, but you didn't click the sarcasm box.