10-07-2012, 03:27 PM
Join Date: Aug 2007
Location: SLC, UT
My Ride: has an iron lung
| While going to feed the horses I got an SES light today. Fuel trim O2 adaptation bound reached. My multiplicative values are +12% both banks and additive values are -.01% both banks. Ideally they should be the same values with opposite signs for multiplicative and additive. This tells me that I'm not getting enough fuel at part throttle. I think I might try what Hagee did and switch to an E39 fuel filter with swappable fuel pressure regulators. This would mean more full pressure everywhere, so idle trims would get to be more negative and partial throttle trims would be less positive. Somewhere in there is a happy medium.
Part of the problem might be the FPR connection as well. Right now it's on manifold vacuum per AA's R3 instructions (though my kit is R2), which intuitively seems wrong. In the stock system it was connected to the intake boot as opposed to the manifold:
Near-zero vac to FPR on intake tube (stock)
Maximum vac to FPR (-16psi) on manifold pressure (S/C)
Minimal fuel demand
Max vac to FPR on intake tube (stock)
Max pressure (up to +10.5psi) to FPR on manifold pressure (S/C)
Maximum fuel demand
My thoughts on this would lead me to believe that the optimal place then, to attach the FPR, would be the y-pipe before the S/C. At light loads it would mimic the light load vacuum of the stock system and at heavy loads the vacuum on it would increase rather than sending pressure to it. Is my reasoning here sound? This would be a more ideal solution than simply increasing pressure to the injectors if what I suspect is true and the entire fuel pressure map is backwards.
The V1 hardwire is complete, with switch and all. Props to Mike at TheBMWPartStore.com for my console, finally a frickin A/C unit mount/ashtray that fits for the nav package, and door sill trim clips. These guys are ridiculously good and so, so speedy.
The meth pump and res are still sitting in the garage. No point really completing that install until my AFRs are worked out and stable.
ETA: I tried to type through my thoughts on how our fuel pressure is regulated, so here's some car pr0n of the garage.
1984 RR Corniche
1989 RR Silver Spur
Last edited by deadwood83; 10-07-2012 at 03:29 PM.