Kurzhuber is a term from internal combustion engine construction and describes an engine whose piston stroke is smaller than the cylinder bore , i.e. the stroke ratio is less than one. Short strokes have a shorter distance between the dead centers than long strokes with the same displacement and thus a higher maximum speed for a given mean piston speed .
There is space for larger valves in the cylinder head of a short stroke cylinder . This allows a higher air or mixture throughput and thus more torque and power . The connecting rods are getting shorter and lighter and the engine more compact.
The Ducati 1199 Panigale , for example, has a stroke ratio of 0.54 with a stroke of 60.8 mm and a bore of 112 mm . Compared to the Ducati 1198 Testastretta Evoluzione, it allows the intake valves to be enlarged from 43.5 mm to 46.8 mm and the exhaust valves from 34.5 mm to 38.2 mm.
Disadvantages are the comparatively higher weight of the piston and the flat, thermally less favorable combustion chamber . The longer flame paths can be compensated for with several spark plugs per cylinder.
- Kurt-Jürgen Berger, Michael Braunheim, Eckhard Brennecke: Technology automotive engineering. 1st edition. Verlag Gehlen, Bad Homburg vor der Höhe 2000. ISBN 3-441-92250-6 .