Hi Simon it was nice to see you today.
1 Just to recap, then.. When you arrived we didn't bother test driving the car with the map you already had (your pic on p3 of this thread) as that map was never going to be a good 'un, it looked like a dog's dinner! I immediately cleared off all the rpm correction, disabled OBD connectivity, zeroed the 0.4ms offset and set about calibrating. During the hour plus we spent driving and calibrating the car (I think you were here 2 hours or so total?) all seemed very well, the flat spot etc you'd suffered previously had gone and the car seemed to behave impeccably on LPG, except for the very occasional misfire at idle - which at the time, and still now, I think ominous. We couldn't determine which cylinder very occasionally misfired at idle (by switching each cylinder back to petrol in turn), as this happened regardless of which cylinder was switched back to petrol. Also, this test confirmed all your LPG injectors were working properly and delivering the same amount of fuel, as disabling any one LPG injector did not affect fuel trims. Your fuel return system is working very well indeed with fuel petrol pressure when running on LPG very very similar to petrol pressure when running on LPG during all driving conditions.
2. We discussed temperature readings and temperature based fuelling correction - Your gas temp seemed to show around 60c regardless of how the vehicle was driven, this isn't the norm as usually gas temp should fall as throughput through the reducer increases (with increasing engine load). Your reducer is better than most in terms of both pressure and gas output (vapour temp) stability but still I would expect gas vapour temp to fluctuate more than your system showed. Sometimes the 60c gas vapour temp reading was higher than the reducer water temp reading (which is only just possible if there is substantial under bonnet heating of post reducer gas vapour). Your gas vapour temp sensor is incorporated in the Oscar pressure sensor, which you have mounted beside the (hot) reducer and not too far away from (and in line of sight of) the driver side exhaust manifold.. I considered this could produce inaccurate readings but discounted this as a problem.
3. During calibration we never really settled to a constant cruise at around motorway speeds with the heater set at various temperatures.. This I now regret! What I'm now thinking could be your problem is the reducer temperature falling with heater (climate control) set at a certain temp with the engine doing relatively low rpm (decent sized engine / auto, won't be doing many rpm at motorway speeds) and I regret not checking your reducer water plumbing (if your reducer water circuit isn't plumbed in properly, reducer temp and hence gas vapour temp may plummet with certain climate control settings as you drive at motorway speeds with relatively low and unchanging engine rpm). Relating to point 2, gas temp of 60c is relatively hot gas and is around the only gas vapour temp we saw, but now I wonder if reducer and hence vapour temp plummeted during your drive home... A vapour temp of 20c might provoke over-leaning of the mixture (most systems over compensate for temperature by default). Also as discussed, your ECU does not support adjustment of temperature related mixture adjustment (so it wasn't possible for me to decrease mixture leaning for low gas temps, which I think might have been a positive in this scenario, which I partly anticipated). Even if it did support temp compensation adjustment, if the above is the case the real fix might be to cure any heater water flow problem to the reducer... To confirm this would need to ask you what the reducer and vapour temps were on your drive home (but I know your laptop battery was flat so you won't have had it plugged in...). In future, monitoring reducer and gas vapour temps, from cold engine start-up, may give further insight into the problem.
4. I am certain that your map is now correct, I set this map based on fuel trim comparisons between LPG / petrol, it now looks almost intuitively correct for most vehicles and does look intuitively correct for your specific vehicle (Jag 3L, a bit different shaped map expected) with your MJ injectors at your reducer pressure. The RPM correction I finally entered (which I zeroed in point 1) is also intuitively correct with -7% max at 500rpm with no load at idle, decreasing to -5%, to -3% with load/rpm and proved to be correct according to fuel trims etc. In point 1 I believe I was correct to disable OBD as your trims at idle on petrol were around +10% but (as far as I remember) were close to zero off idle... Your original RPM correction would have been more positive at 500rpm than at 1500 rpm - that is not intuitive or correct..
5. I have converted many S type Jags, 3L 3etc, to LPG with no problems and with (at least at face value) lower spec ECU (some that don't support rpm adjustment), certainly with lower spec injectors (not as linear) and lower spec reducer (not as pressure or temp stable as your reducer ££'s dual stage reducer) without any issues. In point 1 we have a problem with various cylinder occasional misfires, you originally came in with drive-ability issues, in point 1 after re-calibration we cured all the off-idle drive-ability problems you'd previously experienced (though I still thought the occasional misfires ominous). As said you should really have a valve lube fitted - VSR will lead to a whole range of issues first seen when running on LPG rather than running on petrol... these engines really need a lube system. But your immediate problem may not be VSR or compression related (worth checking now but we didn't check today as the remap seemed to solve your issues), your problem now may be due to over leaning of mixture with cool gas temps (or reducer spitting out liquid gas to the vapour side if it gets too cold. It is also possible, though unlikely, the solenoid on your petrol return system closes (maybe due to duff coil) leading to adverse petrol pressure readings, though I would expect this to generate an OBD error of it's own.
I have a reputation for, and I pride myself, for fixing every LPG issue that comes my way. You have gone home, a 3 hour drive, and suffered an LPG problem... Please look into the points I listed above and if your temp readings do not drop we could maybe come to some arrangement, perhaps where I visit you, to sort your problem. If your problem is not VSR or temp adjustment related and I find I have made a mistake in mapping etc then this visit (involving 6 hours of my driving time plus ful plus time at yours etc) would be free of charge - I have done similar for customers on a few occasions in the past - No worries, a plus for my reputation if anything! I am very certain the mapping / adjustments etc I did today are correct.
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