Thanks. I edited my post above. I missed that. After reading the thread I connected the filter with the first photo of the rail being drilled ... not enough coffee yet.
One other question on restrictions - does anyone know if the ECA acts as a significant restrictor?
Filippo
There are different 'rails' and 'lines' etc.
There is the low pressure feed line coming from the tank, its made up of three main segments. The long run from the driver side of the tank, which turns into the 'short line' by the firewall, which connects to a very short hard line which hosts the LPFP sensor and this screws onto the HPFP inlet. This inlet is a short pipe itself and inside that pipe is the HPFP filter.
The HPFP outlet connects to a 1/4" hardline that runs up to the actual fuel rail. There is a tiny hole shown in an earlier photo of that hole which is bored out, all fuel to the fuel rail goes through this restrictor.
The size of the rail compared to this restriction makes me think the rail acts as a chamber for pressurized fuel. So dips in the HPFP output are cushioned by the pressurized fuel in this rail, which restricts the pressure in the chamber from equalizing too quickly with the lower pressure side of the restrictor.
By boring this hole out too much, when you have HPFP performance issues or the natural up and down nature of the pumps pressure, the rail pressure sensor will see the fluctuation and throw codes. There should be an optimal bore size of that restrictor in relation to maximum flow, where fuel consumption is part of the equation. Just a theory.