What’s the largest possible single cylinder IC aircraft engine?

[Admiral Beez]

Looking at this motor FG-40 4-Stroke Gas Single Cylinder Engine - SAITO got me thinking, how big can you make a single cylinder internal combustion aircraft engine? I assume vibration and weight to power ratios would soon hit a wall.

 

[Howard Gibson]

Admiral Beez,

How big can you make it, or how big should you make it? Just about anything can be made to work if you have the time and the money and you are determined. At what point should you go to multiple cylinders.

Look up The Beast of Turin. Four cylinders. 28.4litres.

 

[AMCKen]

The FIAT has a bore and stroke of 190 x 250mm (7.48 x 9.84 in). This one was rated at 290hp @ 1900 rpm, which converts to a massive 800 ftlbs torque at the same rpm, and possibly more at lower rpms. Note how the fuel is still burning as it comes out the exhaust. Flame front speed and such.

 

[Howard Gibson]

Does that thing even have an exhaust manifold?

If the fuel still burning, or the air heated red hot?

 

[rinkol]

Admiral Beez,

How big can you make it, or how big should you make it? Just about anything can be made to work if you have the time and the money and you are determined. At what point should you go to multiple cylinders.

Look up The Beast of Turin. Four cylinders. 28.4litres.

I've seen old tractors with monster single cylinder engines e.g., Lanz Bulldog - Wikipedia. As for aviation engines, Beardmore built some engines with gigantic cylinders Beardmore Cyclone, Typhoon, and Simoon Aircraft Engines These typically had a 8.625 in bore and 12 inch stroke. According to the article, the aim was to get high power at low RPM so as to avoid the need for a reduction gear. Later, during WW 2, Studebaker worked on the XH-9350, but only got as far as building single cylinder test engines with bores up to 8 in.

 

[AMCKen]

Does that thing even have an exhaust manifold?

If the fuel still burning, or the air heated red hot?

This was just a test so no manifold. Here is the original.

https://upload.wikimedia.org/wikipedia/commons/7/73/Fiat_S76_Record.jpg