Air and fuel molecules do not scale well with the size of engine. Which means that flames are stopped by things like fine metal meshes.

How small can piston displacement be so that the engine still works?

The stresses in moving parts depend on acceleration. Which means that if your individual pistons are smaller and have smaller stroke, you could run the engine at a faster rpm, and get more power out of a large number of smaller cylinders than you could have got from fewer and individually larger cylinders.

http://www.fineartmodels.com/pages/product.asp?content_area=6&sub_area=139&produ...

Mske sure to watch the video on this page!

quote from the page:

"a 1:3 scale Ferrari 12-cylinder engine with the same beautiful sound.  It took Pierre six months of running the engine on his own dynamometer to tune the header pipes so they would give off the same sound value as he had recorded from the engine of the real car.  Once Pierre had the engine bolted together for the first time, it started on the very first try and, since then, has logged more than fifty hours of running time with no failures or refusals to start (It’s probably more reliable than the real engine). "

ShaneG wrote on Nov 13^th, 2008 at 4:08pm:

LOL, thats exactly what I was thinking of when I read the first post!, Was just thinking about trying to find a video of it, when I scrolled down to find I'd been beaten to it.

I love that model, the attention to detail is inspiring.

TSC.

Cox made a  0.010  cubic inch engine..  I can't imagine one smaller than that..

ShaneG wrote on Nov 13^th, 2008 at 4:08pm:


The original Ferrari V12-s are pretty small, too. 166 ccm cylinder displacement, under 2 l total. Which means that the cylinders are smaller than those of Citroen 2CV (2 cylinders at 187 ccm each, total 375 ccm).

How do Ferrari V12 engines perform compared to the more conventional, 4 and 6 cylinder engines of similar 2 l total displacement?

Then have a look at kei cars. Since 1990, their power is limited at 64 horses, and they have an allowance of 660 ccm displacement (reciprocating ones - wankels have 440 ccm, I think), thus there is no point in producing an engine tuned for more power. But before 1990, there was no limit on power, and kei sports cars exist. The displacement limit was 550 ccm 1976-1990, and 360 ccm 1951-1976. The engines designed for 360 ccm kei cars include 2, 3 and 4 cylinder engines. The  4 cylinder ones have under 90 ccm per cylinder.

Honda certainly has long produced 4 stroke benzine engines with 25 ccm cylinders. GX25 for hand tools, and 50 ccm mopeds with 2 cylinder 4 stroke engines.