The normal operating pressure for the fuel rail ranges up to 1000 bar. It is lowered for the best compromise between BSFC (brake specific fuel consumption) and NOx emissions according to the respective engine load and to keep the parasitic energy demand low.
It was determined years ago in engine tests in Winterhur that, under steady load conditions, the influence of fuel injection pressure on specific fuel consumption in low-speed engines diminishes with increasing injection pressure. Thus, higher fuel injection pressures than are presently used in large two-stroke low-speed engines have no real benefit. Should an increase become necessary in the future, for instance in combination with other measures to reduce NOx emissions, the RT-flex system is ideal to cope with it. The additional, parasitic system energy would be very limited indeed, as the increase is about proportional to the pressure increase.
Exhaust valve actuation requires a high volume flow of oil. With an appropriately stepped hydraulic piston diameter on the valve spindle both proper valve movement and low parasitic power could be achieved at the same time. Additionally, the servo oil pressure of 200 bar nominal is variably adapted to the minimum requirement over engine load to ensure a proper function and minimal power demand.