Peter,

Just saw your message- apologies for any delay. \

I suspect the 928S4/GTS fuel system has issues because it is batch fired as opposed to sequential firing thus the hydraulic shock to the system. Even with the two dampers provided the system generates lean spots at two or maybe three specific engine speeds. I doubt anyone would ever have noticed such were it not for the likes of sharktuner and the associated Sharkplotter software. The resulting plots show very clearly that there is a leaning out mid cell at several rpbut what hppens is thatm points and they can create flat spots. If one tries to enrichen the cells involved the rest of the cell content gets over fuelled.

The system is liquid filled and thus non compressible but the opening and closing of the injector causes shock waves that bounce around the system at the speed of sound superimposed over the static pressure. To see them one would need a very high speed pressure transducer- not very practical.