Jens,


Have you noticed the 'long-stroke' engine has fallen out of popularity in the last 15 years, or so?

If you try 'crunching' the numbers; comparing between two engines with the same cubic displacement; one being over-square (short-stroke) and the other under-square, you will find that with the same BMEP (Break Mean Effective Pressure), both will make exactly the same calculated torque.

The single theoretical 'advantage' of a longer stroke, is that the smaller diameter piston has a smaller amount of friction.
But this item is a very, very small factor, in the calculation of the torque.

The reason for the slightly greater low RPM torque of a 'long-stroke' engine, is the smaller mixture and exhaust passages, that require longer to fill up the cylinder, resulting in a lower RPM torque peak.


Some current engines known as 'torquers' are, in fact, over-square, 'short-stroke' engines.
One is the MVVS .91, which has a bore of 27 mm and a stroke of only 26.

So "Long-Stroke" has become no more than a buzz word...