It depends on the improvements in the indicated work and pumping losses
. Valve insulation results to be the strategy with the highest RHCE, due to its direct impact on the volumetric efficiency and pumping loss
Youssef Ismail et al [14, 15] investigated the influence of turbo-compounding system upon combustion, pumping work, exhaust gas recirculation (EGR) rate and engine thermal balance, showing that pumping loss
is the main influence exerting on engine by power turbine.
The inlet valves are held open longer than normal to allow a reverse flow of intake air into the intake manifold, thereby decreasing pumping loss
and increasing thermal efficiency.
This causes pumping loss
, and it is the single most important reason why spark engines are less efficient than diesels.
The reward also recognizes the radical improvements in fuel efficiency realized with the SKYACTIV-G 1.3 via a thorough reduction of mechanical friction and pumping loss
and praises it as an example of the future of ultra-efficient gasoline engines.
Another point to be addressed to the LIVC characteristics is the pumping loss
associated to the longer flow period while the intake valves were still opened, as shown in Figure 5.
- The Atkinson cycle engine delays intake and compression timing to generate a high expansion ratio with low compression, thereby limiting pumping loss
All of these factors however, result in higher friction and pumping loss
penalties than will be measured on optimized and customized production OP engines.
"Up to 10 percent can be lost without causing problems." The pumping loss
is far less than the friction losses eliminated by the new pin design.
It can be seen that the baseline torque, lambda and EGR targets could be achieved with both technologies, except for the lambda target at the 600 rpm operating point due to the tradeoff between an increase in pumping loss
versus an increase in turbine power output.
Furthermore, the improvement of pumping loss
reaches up to 12.18%~20.75%.