rambling possibility driving fuel use...

..... my merc 5.5 V8 and a mate with a CL550 have both experienced the fuel consumption falling off a cliff in the last 18 months, suddenly both are drinking 20% more.... and my R1200GS, its drinking like hell these days too

then another bod on the merc forum popped up saying his was doing the same - he took to a dealer and they gave it the all clear - but when he looked at fuel trims one bank of cyl's is massively different to the other...

And whilst chemistry-physics informs us ethanol infected crap, instead of real petrol has to be in the mix of this decline in mpg, it can't be the only effect - 10% ethanol means what you burn has 6% less energy to push the piston down - but the reformulated water we get today performs much worse than that....

the reason I know a bit about how the BM fuelling behaves, is because my old R1200GS had been going mad for 6 years since an i- level update in 2018 - my 2007 GS was far faster than many - but it was bought first by an old boy and I know the garage that sold it, so it was std - whilst fast, it loved to run rough and stall a lot (the stalling was partly the silly dry car clutch), but the instrument cluster would do somersaults if you tried to ride under 3k rpm and ragging to death in hot weather would cause the power to tail off due to knock after 6k rpm.

when it was sold new it had an i-level update to Jan 2008, and during a dealer service in 2009 I said surely there is a better engine map, it runs like a joke. I was informed “its a BMW Sir, we don't do things like that”.

Role on some 6 years and I find out he was lying through his teeth - after I broke my 335D playing trying to add software to allow me to use a later iDrive knob - the guy said well its so old likely needs an i-level update anyway... Whats that I said... Dealers battled like hell to refuse, but finally did the work and the car came back with its first ever i-level update, going twice as fast, the auto gearbox was vastly better with its new software, some sat nav foibles got fixed, and it had a load of security updates.

All of which meant I found out going back (now) 20 years, BMW have always had a software refresh / update procedure which they review three times a year. And its there for ALL their vehicles (and meant to be just 10 mins of chargeable labour to the customer) - Thus now understanding the poor running on my GS may have been resolved, I started to find out info about my bike. And low an behold I discover the release notes for a mid 2008 i-level update for my GS - of which three addressed running issues applicable to my GS

poor idle stability
changes to cold running enrichment
resolve engine pinging from customer complaints

So in 2018, 10 years after BM should have put it on the bike I got this update - and it all went downhill - slow, horrible with a massive dead midrange and lost all top end grunt. I went back and they reflashed it, but with no change...

I had used a Dynojet PC3 on the old map and had it almost perfect - save that hot weather die back due to knock... But now the bike was a disaster and I couldn't get the PC3 to work no matter what I did - I took it off and it was awful, put it back it was awful - raised a PUMA case with BMW to say you are morons and have written a duff map - PUMA gets the factory tech hero’s to investigate their incompetence and if required authorise (as they can and always have been able to ) that this vehicle can go backwards to the older release, whilst (if they can be bothered) they resolve the software bug in that i-level - they refused to put back the older better map and just reflashed the bike a third time, BUT also reset the vehicle adaptions (which it turns out has always been the std process the dealerships are meant to complete if the engine map is updated - but they NEVER do it) - After this the bike was less bad but still nasty, the midrange hole was mostly gone, and it had its top end grunt back that had gone walkabout for 2 years... And magically the PC3 began to allow me to make changes that made sense - where for 2 years it had just been insanity...

And the reason is that a bike that's adapted to an old map has a load of confused personalised adjustment junk for the old map, that it tries to apply to the new map (but none of it makes sense)... Subsequently I discovered, its all made worse if you have a PC3 on the bike - as it will not adapt ever to the newer map's needs - because the O2 sensors aren't plugged in...

After (I thought) learning all the fun of the fair - I then come across a nuance where my Merc allows a reset of cold weather adaptions and of its std adaptions as two separate functions – And realise maybe my bike runs so horrifically in winter with the cold temp enhancement of the new map, because it’s never adapted correctly due to the PC3 being fitted.

But then trying with and without the PC3 over a winter and getting confused all over again - it now appears a CAT sensor got old and intermittent. And BMW designed it to go mad under this condition deliberately - If one of the GS’ two CAT sensor dies, it deliberately throws the fuelling of the other cyl in massive tail spin and adapts long and short trims to insanity – and the bike transforms in to a lumbering load of recalcitrant gibberish… (you can easily test this by swapping CATS sensors side to side and seeing the exact behaviors swap cylinders) all the while with no engine light to the user, and indeed nothing in its own diagnostic brain either !!!

So back to your K1200 drinking – a clue I believe is in the night rider instructions for the AFXieds – “these need a good signal from the O2 sensors to operate correctly…”
AKA aging CAT sensors on German vehicles allow the engine ECU to find a secret engine map - "drink fuel at all costs"

Oh and just showing the love - the 335D although massively transformed for the better by its i-level update, directly after, I started to notice slip in the transmission when giving it full grief off the line – that was not why I got rid of it – but years later I find out it wasn’t broken - it was a slight of hand BMW, introducing a feature to save the drive line from too much stress – the update brought reduced line pressure to open up clutches under full throttle launches

Wonderful – when these were being used as drag cars and all the world was pushing 900nm through the box with no issues BMW dropped the limit to 500nm from it original 575nm rating – causing the box to attempt self-destruction !!! Got to love the Germans ability to wreck the planet and steal money...