Quote:
Originally Posted by pokeybritches
The reason I think the duty cycle would go beyond 100% with an inadequate fuel pump is because the ECU would continue to try to adapt and add more fuel (just like with injectors that are too small)...
1. ECU adds what it thinks is the correct amount of fuel, based on the map.
2. O2 sensor reports a lean condition.
3. ECU increases duty cycle to add more fuel.
4. O2 sensor continues to report a lean condition.
5. ECU continues to increase duty cycle to add still more fuel... eventually going over 100%.
I think you're right about something telling the ECU it needs less fuel, rather than the car not being able to supply enough. Hopefully VF will clear it up. They recommended I get a Bavarian Technic tool when I had some minor issues with my car (ended up being install error), so maybe it will be my next purchase.
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I believe that under WOT conditions the car should be running open loop and there should be no feedback from the O2 sensor (unless a non-OEM wideband sensor is being used).
If the data logging in this case is giving true information, the fact that fuel pressure doesn't move from 6 bar would indicate that fuel flow demand is being met. I would expect that if fuel demand couldn't be met, as the injector open time increases, the pressure could not be maintained due to flow limitations. A slight possibility of maintaining constant pressure but still not meet fuelling demands could be due to pipe constrictions between the pressure measurement point and the fuel injectors, but this would be remote due to fuel pressure normally being measured in the fuel rail itself.
Rated, do you have any more data logging information available (such as fuel trim, throttle position, etc)? Also, I may have missed it, but does your installation make use of wideband O2 sensors, or is it using the standard OEM ones?