DJB1 wrote:
Here's my question:
Is there adjustment to BRC settings that will correct this? I figure that it needs more fuel at light throttle and much less at mid or full throttle.
Yes, on most BRC systems including yours, the software has a couple of simple sliders to (respectively) adjust calibration at idle loads / adjust calibration at off idle loads.
Perhaps the reason the guy you took it to didn't adjust the off idle settings was because he didn't actually drive it? I won't say anything that could be seen as questioning whether he knew what he was doing, or fobbing customers off with only a bill

Trims being at -9% during closed loop on midrange loads (compared to petrol trims of +3% during same conditions) could be a pointer toward overly rich mixture during high load open loop conditions but that isn't necessarily the case. In my experience plenty BRC installers don't seem to address pressure / nozzle size issues (as per Brian's post)... not usually a problem on most vehicles but can be a problem on engines that idle with small petrol injector pulse duration such as on most Subaru engines. Your short term trims shifting between +10/15% on petrol and around -10% on LPG points to a long term situation that would see more of a difference between -9% and +3% which would point to more of an issue with LPG calibration.
But, even then, since the engine will spend the majority of it's time at low (idle like) and midrange loads, I still wouldn't expect repeated cat burn outs if fuelling seems anything like OK at idle and midrange loads anyway. This may point to a different problem such as failing LPG injectors giving some engine cylinders very different mixture to others - If the BRC system were fitted with BRC's lube system which flows lube into the engine via the LPG injectors I would suspect this to be the case.
Simon
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