I'm back.....
I have over winter been struggling to comprehend what now seems to be very clearly different fuel maps for each individual gear…
I had given up with the PC3, as across multiple winters since the bike's been left on a later 2008 Hexhead 1200 BMW map (installed by a main dealer in 2018) the bike remains unrideable in winter – with the PC3s enrichening need for summer, now vastly over doing things on a BMW cold weather map.
It got so bad I went back to std and tried the BM way - but even then the enrichment in winter is all wrong and it chugs and tries to stall frequently. The only gain, I had at least managed to rebuild some decent base adaptions to further try the next summer with the PC3 back on the bike as I couldn't cope with BMW's terrible fuelling any more.
I now understand more about some of the drivers of the silly running. Real petrol burns correctly at an AFR of 14.7 : 1 (in ideal conditions), but the AFR of Ethanol infected petrol is substantially different with an AFR of 14.2 : 1 when running 10% death fuel.
As the pre 2013 bikes have no ability to correct for this nasty fuel they run ultra-lean and complain. The fix needed wideband CAT sensors and a different ECU to correct between real Petrol and Ethanol infected fuels. Which I believe only came on 2017 model year bikes. The later design wideband sensor can be forced to take the fuelling in a certain direction and from this calculate the actual AFR rather than just an O2 reading.
Thus it was back on with the PC3 for summer 2024 and I was making amazing inroads into the way the bike behaved using a new method to work out how badly it was running, by mapping the bike based on the trip computer info.... Using the ave consumption reset, for a given throttle setting and revs you can see if what you feel is happening, is really driving the fuelling right or wrong - allowing you to work out if rich or lean... The ride-ability and the power improved, but I was also able to remove stupid levels of enrichment in certain areas and saw significant gains in MPG too.
Clearly BMW later realised it was a mess as riding at the same speeds you can find better running and huge economy improvement in the twin cam mapping - its far less terrible... often you see 70mpg for the exact same conditions the older Hex will say 54mpg for same road speed and gear.
Then as is now usual winter came and the bike wouldn’t behave – I bought two new CAT sensors, ripped off the PC3 and went to std to retry and get a decent winter adaptive map. But its terrible – as I have said all along the change from the OEM factory Map, to the year later update, doesn’t function correctly in the winter – being vastly over fuelled.
I can find a weird gap below 12C its normally OK, above 14C its usually OK, but in between its a free for all of hell - all along any temp it can be accompanied by random fits of idle idiocy. And if you scan back through all the madness of earlier post it always runs like a dream whenever it's above 25C
But now my std journeys have changed, fuel consumption seems to be falling off a cliff… And what was mildly puzzling with the PC3 on the bike is now very clearly a BMW feature. If you ever reset the engine adaptions you are expected to run the bike through the gears, as some wrongly believe to set up the gear indicator. That is not what is happening – the gear indicator works just fine all the time –
but every gear does get a different voltage output – that appears to be fed back to the engine ECU allowing BMW to run a different fuelling map based on each individual gear.
On the face of it that seems like madness, but remember this was early days mad injection on a budget… Real systems use a MAP sensor to get far better info on fuelling need
https://sensorguides.com/map-sensor...e-to-understanding-engine-management-systems/ or the lesser system of a Hotwire Mass airflow sensor as a poor second best. But all we get is joke fuelling from bodge and guess it. So some brain surgeon at BMW must have dreamt up guess it by gear, to add some form of load compensation on a shoestring
It easy for ANY of you to check, rather than just shout me down and lie – get to normal operating temp - find a smooth flat road no wind - Ride in any gear holding constant revs, and toggle round to ave fuel on your trip meter – now press reset (long press of info button) and give it 5 seconds, and it’ll show a stable reading of x mpg. When you see circa 53mpg for whatever condition you are in, the thing runs beautifully, and with no load this can transforms to 65 mpg and it’s still very happy. But when it chugging, juddering and behaving like a pig, it will be reading 42 to 45 mpg.
Now go through the gears for same throttle setting and revs ( say 2,800 rpm @ 10% throttle) – 1st will be at 35mpg, 2nd will be 42 mpg, third will be 46mpg and suddenly by 4th it will run happily and show 53mpg …. And keep going 5th may show 65mpg – what a load of insanity !!!
Don’t believe that, - reset ave consumption and ride all day at low speed, thus maintaining only low gears and your ave MPG will plummet to 42mpg, but ride in 4th and 5th gently and it will go above 60 mpg – which is the opposite of how the world should work. As wind resistance and trying to maintain the higher gears would tend to need a fraction higher throttle setting – so that later map is plain stupid and badly written, and I guess came about trying to ensure wild throttle opening's in low gears wasn’t met with sudden increase of air flow overwhelming the std fuelling map ...like having no accelerator pump on a car, where it won't pick up.
