#109778, "0 psi fuel cut, has this ever been solved?"
I keep getting fuel cut at the 0 psi transition point. I see dozens of posts like this in the archives, and only one thread where the problem was solved (but that was from magnetic interference from the electronic boost controller).
It is definitely fuel cut, as noted by the sudden super lean AFRs. It is not precipitated by a momentary rich point right before 0 psi, such as you might expect would cause the ECU to lean out. Fuel pressures are steady during this time. Injectors have been recently cleaned and balanced. It is independent of RPM. Car has zero issues beyond this, no CEL, no vacuum leaks. There is nothing mechanical happening here, I am certain it is only the ECU's response to MAP voltage behavior.
Voltage on the MAP line is monitored by a greddy e01. Voltage does not go above 4.7. I have played around with FCD settings ranging from 4.3 to 4.7. Nothing seems to work.
I don't see fuel cut under a WOT scenario where the transition from vacuum to boost is quick. I do see fuel cut if gradually transitioning through 0 psi at partial throttle, or hovering at 0 psi. This happens A LOT during normal city driving. It's annoying.
The e01 shows interesting phenomena. When MAP voltage slowly increases while increasing mani pressure to 0 psi, there is fuel cut. When hovering constant at max voltage (<4.6 or <4.7V) at 0 psi fuel pressure there is fuel cut. When slowly decreasing from max voltage to 4.5V as mani pressure decreases from 0 psi to vacuum, there is fuel cut. It leads me to believe it is not just a specific voltage that causes fuel cut, but a specific voltage over time .
#109779, "RE: 0 psi fuel cut, has this ever been solved?" In response to Reply # 0
I thought about it some, and decided to force the ECU into open loop at 0 psi by using the e01 to output 5V to the TPS when mani pressure reaches 0 psi. I think the ECU sees a rock steady max MAP voltage as unusual so it cuts fuel (maybe the programmers suspected a huge vac leak would be occurring when the TPS is showing only partial throttle and the MAP pressure is close to atmospheric). When you think about it, near atmospheric pressure should only be seen in a NT setup when WOT. Thus making the ECU sense WOT anytime the mani sees 0 psi should be closer to what it would expect.
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