Problems were due to a combination of issues.
3L BMW straight 6 which doesn't need a valve lube but a lube is fitted. The lube nozzle isn't a proper very narrow gauge lube nozzle, it is just an injector outlet spud with 3mm internal diameter, so lube droplet size would be massive and lube wouldn't atomise properly... even if the nozzle was in the correct location just after the throttle body, but the nozzle is fitted just into the upper plenum area. Actually any lube system on this engine (if it needed a lube) should be multipoint because the engine features idle-air, with any lube other than multipoint on this engine while the engine is idling the lube will just be dripping into the vacuum of the plenum and pooling. The 6cyl engine in X5's slopes down towards the back, lube was pooling towards the rear of the plenum and richening the rear bank of 3 cylinders. I turned off flow of lube, to allow the pool to clear in time, because this engine doesn't need a lube and because of all of the lube issues.
Previous issues with the LPG system, failed lambda probe and lube system had caused the petrol ECU to learn incorrectly, fuel trims were way off combined with a bank trim issue and BMW 'smooth running' values (which are like a mini fuel trim for individual cylinders) were all over the place, particularly affecting cylinder 5. The petrol ECU couldn't complete IM readiness so long term fuel trims were stuck at -8.5% on both banks but stfts were maxed out on bank1 and minned out on bank2 due to too lean LPG calibration, incorrect LPG map shape and the lube issue. System was calibrated with too much pressure (1.4bar) with multiplier of less than 1 over most of the map and idle ginj of only 3.7ms with 70c gas vapour , I re-calibrated with well suited map shape at 1.1 bar.
Following the changes I made we ended up with an engine which idled and drove perfectly, ltft's still at -8.5% on both banks and stft's of +8.5% on both banks at idle on either fuel and close to zero off-idle. The petrol ECU will now complete IM readiness and the fuel trims will all be steered close to zero, hardly changing on either fuel..
Reducer pressure isn't the most stable and was falling a little below the changeback pressure that the installer had set (or more likely hadn't bothered to adjust in the first place). Following my changes the vehicle will drive totally on gas at full throttle up to the red line, and though ginj approaches 100% duty cycle mixture remains rich at full load. The vehicle was switching back to petrol during the over-run, I sorted this by changing rpm setting from cam sensor to petrol injectors; with the petrol injector setting the LPG ECU doesn't change back to petrol due to lack of rpm pulse detection.
That's 3 vehicles with long standing problems each coming from many miles away sorted today..
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