07-16-2015, 12:23 PM
Join Date: May 2005
Total Cats: 779
OEM NB2 fuel system pressure creep
One of the race cars in our shop is an MSM with a 100% OEM fuel system. It's had a problem going lean under sustained WOT we haven't been able to diagnose.
Running N/A as a SuperMiata
Stock NB2 engine tuned for 140whp on E85.
MS3 pro with DIY harness
Logged voltage in race conditions, steady 14.0~14.1
Idled for 30 minutes and fuel pressure crept up from 60psi to about 67psi with gas cap removed.
Replaced OEM pump with 190 High Pressure Walbro, no change.
It's got us scratching our heads. We're guessing it has something to do with either the returnless fuel system or some mystery table in the MS enabled that we don't know about.