View Full Version : Rod to Stroke ratio;

02-12-2010, 10:00 AM
Respected motor head Smokey Y. stated that a2.2 to 1 was ideal he also wished con rods could be infinite. Engine design parameters don't always allow for this . If you can't reach the ideal what we can do is exploit the positives minimize the weaknesses. The positive start around TDC a piston attached to a long hangs around TDC in actual time and crank degrees keeping the combustion chamber smaller longer.A short rod engine's piston at 20 degrees is farther down the cylinder making for less potent charge might as well open up the exhaust valve early start scavenged that exhaust .Remember this after the initial pop the explosion is chasing the piston not pushing it.At BDC it's the opposite L/R piston move quickly after 90 degree's good stuff for the intake stroke the quick drop in pressure is sustained longer because of quick piston speed at this part of the stroke giving the intake charge Lot's of momentum which can lead to over 100% volumetric efficiency.And the LR.will deliver it more efficiently with less side load on piston."Any information right or wrong is food for thought"