The model of slider-link driven compressor, presentedin the previous parts of the study, was improved totake into account capacity losses due to blow-by throughthe clearance between the piston and the cylinder. Pistonsstroke to diameter ratio of a compressor was optimized inorder to achieve the highest compressor efficiency. Optimalpistons stroke to diameter ratio was determined, butthe influence of this parameter found out to be relativelysmall. From analyzed parameters the highest influence oncompressors efficiency has the clearance between the pistonand the cylinder.