this post was submitted on 02 Dec 2023
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Was the Wankel engine really a step forward though? I'm a gearhead who does all his own car maintenance, up to and including engine swaps in the past and retro-modding bigger turbos and aftermarket fuel injection systems into my cars (Datsuns in the latter case). That being said, I only know the very basics about rotary engines. I've always admired the Mazda RX's from afar.
Mazda, who by no means makes a bad gasoline engine, could never get a rotary motor to last well or to have anywhere near decent fuel economy. Also, the rotary design was tried for a while in at least refrigeration compressor applications, where it blew up there a lot more than the other types of compressors as well.
Yea. They have worse efficiency. To get better efficiency from them you would need to run them hotter (afaik), and if you do that they would last even shorter.
It's great if you want a smaller but still strong engine, but it's not efficient and those seals are a big problem.
The problem with the rotaries is a result of the technology of the time and funding.
They are inefficient because they lose compressed fuel and air as the seals pass over the holes for the spark plugs, which can be largely solved with laser ignition. They are less reliable because of the design of the apex seals, which can be solved by using a roller instead of a blade. Both of those major issues with the rotary could not be solved with the technology of the 60s-00s and the tiny budget available. There are other issues that hold back the design, but those come down to metallurgy and manufacturing processes. Mazda did a great job trying to make the rotary work and it almost killed them.
The other issue that gives then an unreliable reputation is because you can't treat them like a piston engine and people treat them like a piston engine. Hard to fault the knife for breaking when it was used as a pry bar.
hoo lee I've never even thought about that, that sounds sick as hell
The argument is, though I’m not qualified to assess it, that Wankel engines are simpler, smaller, more power dense and, if allowed time to develop, would be an improvement on the traditional ICE. It’s very difficult to assess where we would have ended up and a little by the by, given we need to move away from burning fossil fuel.
That said, do check out LiquidPiston’s evolution of the Wankel engine. It does sort of look like they’ve solved a number of issues a traditional Wankel engine has.
The basic problem with Wankels is that the geometry of the combustion chamber (such as it is) is constantly changing, which inevitably results in incomplete combustion compared to traditional ICEs. This leads to lowered fuel efficiency and greater emissions; the emissions problem is solved with an additional combustion chamber for the exhaust gases, but this consumes more fuel and lowers efficiency even more. It's just a fundamental problem with the technology that no amount of development could ever fix.
It still has corners that need to have a moving seal. This is a huge issue.