Is it possible to make a 4 rotor rotary engine by putting together 2  2-rotor s?

The problem is getting the crank shaft. While two two rotor engines could be bolted up in line- that makes for a long engine.

It has been done:

https://www.roadandtrack.com/motorsports/videos/a3...

https://definedautoworks.com/mazda-rx7-engines-4-r...

Mazda raced a 26B engine for a while, which was basically two 13b's in a single assembly.

Are you kidding? A rotor engine is nothing but gaskets! What kind of monstrosity is that?

Yes.  I have seen people put together a 24 cylinder engine by bolting 3 V-8 crank to crank.  Fuel mixtures and volume can be some what of a problem.

Do you think rotary engines might have been a bit more popular with a different name?

Yes, the 4-rotor Mazda 787B won LeMans in 1991. Mazda offered a 3-rotor in the 1990-1995 Eunos Cosmo.

But would you believe *twelve*? This guy tied three banks of four rotors together to fit in the size of a V-8:

https://www.caranddriver.com/news/a15358002/amazin...

if your an engineer then no problem , if your not an engineer then you have no chance . and you do happen to know the fundementals on a single lobe to a twin lobe constuction and design . .

I think in the early days, someone did make an experimental 4 rotor:  NSU, Mazda or might have been Mercedes.  As I recall, it was mad powerful - - but as with a conventional engine, the frictional losses went up disproportionate to the power increase and it negated the value of compactness.  There are 1 rotors . . . a 2 rotor is proven and can be as powerful as needed.

ABsolutely - and it's been Done Before. You do have to make a new crankshaft though.

Yes, but there are issues. The two rotors Wankel have specific components on the outer ends, which will therefore require replacing with custom parts as those would be 'inside' the engine for at least two of them.

You can google "4 rotor Wankel" and see that such builds have been made.

Sure, its theoretically possible but its not practical in any sense of the imagination.