1950s engines aren't a fair comparison, because they were developed without the aid of CFD and FEA, both of which will have massively helped the Wankel catch up. So taking into account that advantage AND the fact that reciprocating engines had more development time, you're really looking at about 1970s or possibly early 80s engine design (to compare with turn of the millenium Wankel).

And you'll see that in every way except lightness the Wankel is a failure. And because of the inherent disadvantages it can't ever catch up either, regardless of what fancy things the engineers do, or whatever marketting crap the marketers come up with.

I disagree on the first part, the CFD have aided the Wankel but the piston engine has waaaaaaay more development time and that supports my argument not yours (why did you put an "AND" there?). The first reciprocating internal combustion engine prototype was built around 1850. 1950 was generous. 1980 is dreaming. You think they didn't use computers in 1980?

The Wankel is a failure? Really? Well that's my cue to end this discussion, since you prove for the millionth time how closeminded you are.

Since you mentioned it though, the Wankel engine type generally has a thermal efficiency of 20-30%, exactly the same as a typical 4 stroke piston engine. I'll just mention one example, that of gas turbine engines which typically have thermal efficiencies of over 40%, and as high as 60%. And let's not talk about electric motors which can reach 99%. So I'd say the reciprocating engine is just as much a failure as the Wankel. Just FYI the most efficient internal combustion piston engine in the world is a two-stroke, a ship engine with 51% thermal efficiency - almost 10% more than the most efficient four-stroke.

In 1980 the computing ability was a lot less than when the Renesis engine was made, using much of the R&D already done on gasoline engines, which is why I chose 1980 as a similar level of development. Since then I would admit that gasoline engines have forged ahead.

The AND was because I wanted to stress both points together, rather than independently.

What is your point about gas turbine engines, or electric motors? Why add those to this discussion between Wankel and Recip? Between the two, the reciprocating engine has a better combustion chamber shape, similar thermal efficiency, lower frictional loses (believe it or not, but I don't have values available), lower wear, lower oil consumption, requires lower tolerences, is marginally heavier, can work with diesel, has greater output per unit flow of gasoline (real efficiency, rather than thermal), has (in my opinion) greater tuning potential before the basic concept becomes the weak link... Need I go on?

Wankel has nothing other than size, weight and the sound produced to really support it technically. It is also a bit of a gimmick, which ensures that Mazda sell it to be different. If it was that good why aren't other manufacturers copying it? Dyson 'invented' the dual cyclone vacuum cleaner (they didn't actually invent it really, but made the design commercially viable and compact), and now everyone copies it because it was a good thing. Good things get copied in industry, and it's a surprising way of telling what is really good and what is a loss-leader or marketting gimmick.

This is a slightly off-topic question but does anyone know if the efficiency of an engine is increased if a fluid-fluid heat exchanger is used to heat the fuel using the hot coolant?

The point is that rotaries and recips have been aided equally (more or less) by computers.

My point about jet and electric engines was (I thought it was clear) that as far as engines go, both of these two (rotary and recip) are pretty low on efficiency, so I wouldn't call one of them a failure and the other a success. As far as power producing units go, neither of them is a real groundbreaking success. They are both quite a bit below average. Of course they are convenient, small, cheap, but that's a different matter. Mechanically they are both "failures" on an equal level. This was a response to your calling the Wankel a failure, and my point is that yes, it's a failure, just as much of a failure as the recip is.

Listen man, I don't support either type more than the other, I actually prefer recips since I'm most comfortable with them, have more experience. I also agree with many of the things you say, but none of those make the Wankel a failure, or the recip a 'proper' engine and not the Wankel, like you said. And certainly and most importantly, none of those make rotaries unsuitable for LFS.

Quote from wheel4hummer :

This is a slightly off-topic question but does anyone know if the efficiency of an engine is increased if a fluid-fluid heat exchanger is used to heat the fuel using the hot coolant?

Of course it is (the thermal efficiency), this way the heat is recycled, not lost.

Maybe I should have said 'relative failure' then. Haven't some lab gasoline engines got to about 50% thermal efficiency? Although I gather the techniques used wouldn't (currently) be even vaguely suitable for a production engine.

Quote from Kosmo :

Of course they are convenient, small, cheap, but that's a different matter.

Electric motors are high efficiency and small. But that's only one part of the problem. When you look at the system of an electric vehicle as a whole, you realize that there are fewer advantages then it seems. For example, you have to get power to the motor. The best way to do that is batteries, which happen to be really heavy when you have alot of them.

wankel has some inherent flaws not due to bad engineering but due to its very nature. that is what tristan is talking about. pretty much like why they are not using two strokes any more... even though they have more power less weight and less complexity than 4 strokes, the 4T ones are now better because no matter how much you develop a two stroke you can't manipulate the gases burn as neatly as you can in a 4T.

imnsho