The Wankel Engine - Why I love it

I have a sincere passion and love towards rotary engines. The rational choice nowadays is going electric, if you really want a petrol engine the piston engine is the better choice. However, nothing converts fuel into noise as effectively as four angry doritos spinning a shaft at 11.000 RPM.

Theory

The rotary engine was comprised in 1933 by Felix Wankel and never really took off*. The asterisks are important here because all of this is only half true. Wankel did gain the patent for the engine in the form in which it was eventually put into production. The engine was dreamt of earlier, during the roaring 20s. The plans for the engine originated in discourse with others like Willi Strauch, another German-then-Nazi engineer also based in Berlin. Strauch went on to fight Wankels patent later on. Strauch is a personality himself and worth his own story (another time).

Interestingly, Wankel didn't have to deal with the problem of getting his engine running. He left all the hard engineering of building a reliable and powerful engine to companies licensing his patent.

Everyone in the automotive world was on board with this and wanted to try the new concept: VW, GM, Toyota, Renault, EVERYONE. Famously, even the original mid-engine Corvette ("Aerovette") was based on a Wankel engine. However, no manufacturer seemed to get it running good, reliably and powerful enough to actually utilize it.

Except there was NSU. NSU (which later was folded into Audi/VW) built two cars containing a running wankel engine, both suffering from low reliability. There also was a little japanese company called Toyo Koruko Kogyo ("Mazda"), which liked to do things differently. Mazda eventually ironed out the kinks of the engine, creating some of the most legendary automotive experiences known to date.

Pro & Con

In the following I will talk about technical details mostly in reference to the 90's Mazda-Spec rotaries.

Benefits

Due to the technical design of the rotary, it is technically a 1-stroke engine: All 4 combustion strokes happen simultaneously in the engine. Also, it has a symmetric design. Adding a second rotor to the engine makes for an inherently balanced and smooth experience. Rotaries produce little to no forces except the torque at the output shaft. Also, because the rotating assembly spins at a third the speed of the output shaft the engine can rev really high with little consequences to the rotating assembly. RPMs in excess of 11.000 are not uncommon, with stock engines usually topping out at 9000. The simultaneous cycles also allow for a simpler, lighter and more compact construction: A third as many moving parts, a third the size, a third the weight.

Downsides

Rotaries are Divas. They need proper maintenance, proper oil, require premixing fuel with oil and guzzle a lot of fuel. Also, they do not have the torque at low RPM to really do anything and ideally also need a turbo to really make power. Rotaries also suffer from reliability problems due to internal seals in the engine wearing out and breaking (due to improper maintenance or bad driving habits). If you do everything right, rotaries are great. If not, well you are in for an engine rebuild.

Why use them?

If rotary engines are really that bad, then why not simply use a cheap and reliable alternative, the piston engine (or electric)?

Using a different engine concept is fine and the sensible choice. However, there is a certain breed of people that like to do things differently. They are called car enthusiasts and all your rational reasons are fine and dandy with them, just not applicable. Enthusiasts believe in certain ideals, like no car ever being perfect. Also, driving needs to be emotionally engaging to them. The rotary really fits this niche for multiple reasons:

• the linear power delivery makes for an extremely predictably yet smooth driving car
• revving an engine out (and the engine liking it) is somewhat fun
• religiously taking care of a car is part of the enthusiasts identity
• the noises associated with a rotary are really unique yet really appealing
• the rotary always represented the underdog and enthusiasts like a good underdog story
• rotaries have heritage with the 787B winning LeMans against all odds

As stated, there is no good reason for rotaries, they are just a fun concept to certain people.

Production vehicles

Over the years the engine went into many different vehicles.

NSU

NSU as the first adopter used the engine in two cars, briefly. These were somewhat bad cars and initial manufacturing problems leading to reliability issues didn't help. NSU Wankel cars are essentially unicorns. Really rare, really important, no one has them.

Cosmo

The Mazda Cosmo was a sports Coupe with a 2 rotor. It wasn't that much a serious car as a proof of concept that paved the way to other cars in the 70s. The Cosmo had a 1 litre engine producing 110hp revving to 7000RPM, impressive numbers back then. It did this with carbon apex seals, which fixed one of the design limitations of the rotary. Its successors included the whole RX lineup, another Cosmo and a Rotary pickup (which unfortunately never took off, it could have been a Mazda Syclone; the car to predate the SUV craze by 50 years). The Cosmo (along the S600) opened Pandoras box and defined an era of cars.

RX-7

The RX-7 was a 2 rotor sports car. This abandoned associated comforts in exchange for a really sporty chassis. It was the Cosmos spiritual successor. The RX-7 came in three major variants. The SA (-16, -22C, FB) was the first iteration. It came in as an extremely light and well-balanced car with impressive driving properties. This RX-7 was cheap, a really good car and could keep up with basically any car produced at the time, including Porsches. This RX-7 got many upgrades and refreshes during its lifespan. The succeeding FC followed a different formula, the Porsche 924. The FC was essentially a 924 with a rotary engine. Its most desirable variant, the Turbo III, also came as a Roadster / Cabrio and was pretty successful in the domestic market. Abroad the VW Audi Porsche 924 existed. In the 90s, Mazda introduced the Miata. A light roadster that covered the entire lower sector of Mazdas sporty car sales. The third version of the RX-7, the FD was made as a more expensive more better sports car compared to the Miata. It didn't need to be cheap or comfortable, it was made to follow the lineage of rotary sports coupes.

In many ways, it is a forbidden fruit. With prices ranging from 30 to 50 thousand € here in Germany people like me can just stare at pictures, sobbing over the perfect curves of the FD.

RX-8

In the 2000s, Mazda tried to back up the FD with the RX-8. The basic recipe was the same as the RX-7s. A RWD manual sports coupe with a 1.3l 2-rotor up front. The car also needed to be light, nice to look at and perfect in balance and driving dynamics. Unfortunately, the RX-8 wasn't as good as its predecessors. It was a weird combination of different ideas that on their own could have been a game changer yet together made the car into a half baked mess. Mazdas aggressive pricing sure helped sell the car, however it was not enough to survive in the market where cars like the Audi TT or Nissan 350Z existed. The market of the 2000s was looking for something that was not an RX-8. The cars of the time needed to be more luxurious, more livable and more reliable than ever. The inefficient, neither really sporty nor really comfortable RX-8 was, well a combination of half-baked ideas.

This means there are a lot of used RX-8s out there. Nobody wanted to keep a creeky uncomfortable gas-guzzler when they could also have an Octavia wagon to haul around family or a TT to go properly fast on a budget. People interested can readily find and buy RX-8s, the one thing it has going for it is the really balanced chassis. The engine doesn't handle turbocharging well and will eventually fail on you sooner then the rest of the car.

The RX-8 tried biting of more than it could chew. It tried to be a compact with the looks of a sports coupe, it tried to have the handling of a F1 car with spiritually a motorcycle engine, in short it didn't work out because it was mediocre at everything.

RX-9

A few years ago Mazda announced the Wankel was coming back. Mazda built some prototypes like the Nagare Furai since the RX-8, but the first production vehicle since then is the MX-30 which leaves me with mixed feelings. It is a weirdly proportioned SUV with a hybrid powertrain. The new rotary, the "8C" serves as an onboard compact generator ("range extender"). It has some interesting new quirks and looks to be optimized for reliability, however I can't really say anything about it since I haven't teard it down yet.

Then there is the RX-9. It is supposed to be a propper sporty car capable of keeping up with your AMGs and Vettes, it is supposed to bring back a golden era of japanese motoring. Its stated design goal was to follow both the Kodo design language and the RX Vision concepts design. This makes it look (from what we have seen) good, but not even close to the RX-7s style. The RX-7 was the flagship of a new era of auto design and still looks stunning today, the Kodo design language works on something like a CX-30, but on a sports car? Also, the RX-9 ditches a lot of the classic sports coupe design elements and choices making for a boring AMG GT looking luxury tourer.

Additionally, this car was rumoured to not have a rotary at all and instead be a hybrid I6. With added luxuries and creature comforts the RX-9 would be an expensive, fat GT in a field of sporty every day cars at (sadly no longer) reasonable prices like the Supra or TT. This would mean a total break with everything the RX-7 stood for and I hope Mazda will not follow through with this. Such a car would not deserve the RX badge and should be marketed as something else entirely. Similar to the RX-8, that would not capture what Mazda stood for and be seriously ludicrous. Mazda has proven with the MX-30 that they are more of an suede engineering marvel than the original japanese passionate perfectionist.

New rumors (as of Q2/23)

As of now, we have new rumors to talk about. Some of Mazdas patents surfaced. The patents show a sporty car with a hybrid powertrain. This is not good for hardcore enthusiasts like myself, but I have to concede that the electrical assistance really complements the Wankel. The powertrain showcases a three rotor (!) possibly based on the 8C powering the rear (!) with electrical assistance on both axles. This 25C would be absolutely insane and I'd love to have one ASAP. Also the patents for new crash structures look not to bad actually. I am concerned that this car will carry over to many creature comforts and 'engineering improvements', robbing the car of its soul. Also possible pricing is concerning. I hope they will target cars like the M2 or GR Supra and not the M4 CS or GT3, making this a 50 Grand revolution rather than a 200 Grand oddity stored away in some rich guys warehouse.

TL;DR

A sizable group of individual car enthusiasts has a soft spot for rotary engines, because they are light, powerful and incredibly engaging. Although they are difficult to work with, a number of mainly Mazdas where produced with the engine. The car standing out from the crowd is the third generation RX-7, because it is the biblically accurate perfect sports coupe / car. Mazda announced the RX-9 as successor in the series, however it is shrouded in mistery and secrets right now. I (among others) hope Mazda understands what makes the RX-7 good and can capitalize on it. Also, I put my money where my mouth is and own a first gen RX-7.