DIFP lower than command with fueling modifications
Posted: Tue Sep 29, 2026 5:52 am
Hello. I am tuning an FK8 with xdi evo fuel pump, DW300c rear pump and 1530cc injectors running about 2bar of boost.
I have seen that DIFP falls at high rpm/boost. If I lower the boost, problem still persists but it shows up in gradually higher rpm. I suspect the rear pump, replaced with a brand new same piece (DW300c), still nothing, I checked rear pump voltage at idle and it is steady 12.6-12.7v while on the battery I read 14.3v. Could we need a pump wiring kit in FK8 for DW300c pumps?
Note: although you can't see it at this log, if you keep the dyno pull, DIFP equalizes again with DIFPCMD above 6800rpm.
Note2: I have used the XDI recommended settings in the 'MODS' list (both hardware and feed forward).
Note3: AF is relatively stable and close to target.
I have seen that DIFP falls at high rpm/boost. If I lower the boost, problem still persists but it shows up in gradually higher rpm. I suspect the rear pump, replaced with a brand new same piece (DW300c), still nothing, I checked rear pump voltage at idle and it is steady 12.6-12.7v while on the battery I read 14.3v. Could we need a pump wiring kit in FK8 for DW300c pumps?
Note: although you can't see it at this log, if you keep the dyno pull, DIFP equalizes again with DIFPCMD above 6800rpm.
Note2: I have used the XDI recommended settings in the 'MODS' list (both hardware and feed forward).
Note3: AF is relatively stable and close to target.