BMEP characterizes the work received from each outbreak, and in most cases, can serve as a criterion for estimating the crossing of the working process (the mean effective pressure can be low when the forced the working process, if the mechanical losses for any reason, an abnormally large). Four-stroke engines with supercharging the mean effective pressure 14-24 kg/cm2. Two-stroke engine with a supercharged pe = 10-13 kg/cm2. In four-stroke racing engines naturally aspirated ranges 10-13 kg/cm2, a two-stroke - 5-7,5 kg/cm2. 7. The ratio of stroke to the diameter of the cylinder (S / D) has always attracted the attention of designers. For many years, a trend towards a decrease in S / D. For most of the racing engines S / D is in the range 0,9-1,1. The transition to the use of motors with a short stroke had a number of reasons. These engines are lighter, since the surface of the cylinder at a given volume reaches a minimum at S / D = 1. Consequence of the large ratio S / D is a high load of the lower rod bearing due to increased centrifugal forces of rotating masses. This burden is not offset by a decrease in translational inertia of moving parts by easing the piston. Connecting rod bearing - one of the most vulnerable places a high-speed motor, so overload it is very undesirable.