Selecting a suitable stroke / bore ratio when combining variable compression and Early Intake Valve Closure (EIVC)

Abstract

Increasingly strict fuel consumption and emission legislation is forcing engine developers to use combinations of technologies that complement each other to produce high potential for cutting fuel combustion.

For this reason, IAV has examined future-oriented technologies initially for their individual potential and then with a special focus on their complementary potential. The combination of geometrically variable compression (VCR) and early intake valve closure (EIVC) proved to be especially promising in early studies. It transpired that both technologies enhance the inner efficiency. It is worth noting that while early intake valve closure reduces pumping losses, it is detrimental to combustion quality and residual gas tolerance due to a loss of temperature and turbulence. This comes from the smaller tumble energy with the reduced valve lift and from cooling the cylinder charge under intermediate expansion to BDC.