Shiftcam musings.......

[Hann]

I don`t know about most folk but i was originally under the impression that the Shiftcam only operated at 5,000rpm and over - dyno graphs suggest this if you`ve ever seen a printout of the power and torque curves, there is a definate bump at 5k.
Over the near-four years of ownership of my 1250 i`ve noticed the occasional single `pop/burp` from the exhaust when squirting out from a corner for example in the lower gears and wider throttle openings.
Now, this little detail got me thinking as to the origin of this pop/burp, as have others as mentioned in the thread here, and when these questions enter my ikkle bwain i can`t let them go so in the name of research and development, footerin`, and - because according to Mrs Hann i can`t leave anything alone - i thought up and made this small gadget that is hooked up to the Shiftcam circuit and will let me know just when the Shiftcam actuator is energised.

The green LED is lit when the low lift cam is being used and it will switch over to the red when the high lift cam is used.

I took it out for a test ride and the results are in - Shiftcam operates almost continually when riding and not just at 5k and above, is imperceptable in operation and often switches much earlier in the rev range than i thought and can be made to work at engine speeds as low as ~3,000rpm according to load and throttle. The pop mentioned in the other thread coincides with switching at lower engine speeds. So it`s a bit similar to what BMW say in their (vague) technical description, in fact.........!

The gadget;



I did a video but it`s a bit crap, i mounted the GoPro on the tank bag so it`s a bit shakey and the low morning light produced loads of glare but i hope you can see enough to get the gist; the first bit of the vid shows what happens when going uphill in the higher gears or overtaking when you open the throttle, the middle bit is on a light throttle in third gear but letting the engine rev out - shiftcam only switches when at 5k and the last part of the vid shows shiftcam operating when squirting out of a slow corner when it operates at about 3k.
So it seems the operation of Shiftcam is more to do with throttle opening than engine speed alone.

So there you have it, you`re all now going to tell me that you knew all about this already......

 

[JoeBiff]

Interesting.
I have a inkly feeling it’s the shiftcam operation which causes some of the lurches in the 1300 ASA system when it’s running at low revs but suddenly decides it needs to drop a gear and increase the power available when going up a hill (for example).
It’s probably something in the software that needs further development but overall the system is PDG.

 

[littleade]

As I ride like miss daisy I could do with borrowing that to see if my 1250 ever uses the high lift cams....or not

 

[Hann]

As I ride like miss daisy I could do with borrowing that to see if my 1250 ever uses the high lift cams....or not

I`ve ridden a few times now with the indicator gadget and unless you never open the throttle over about half way i can guarantee that the Shiftcam will be working.
It is constantly switching between hi and lo lift cams, basically any time you open the throttle wide enough regardless of gear or engine speed it`ll switch, you can even get it to switch when blipping the throttle off idle which is something i thought would not happen.

Another interesting facet to this is Shiftcam seems to be related to the pinking issue which some of us 1250 owners are experiencing.
Open the throttle to accelerate and you`ll hear the pinking, but as soon as the Shiftcam switches to the hi lift cam the pinking stops....
Have BMW made the 1250 so lean and `on the edge` to pass Euro 5 that it has compromised the running of the bike and Shiftcam is not - as sold to us - as a performance-enhancing feature but necessary to get the engine to pass emmisions tests at the moderate power settings they`re tested at but has still has enough umphh when the Shiftcam operates to satisfy riders desire for performance...? Dunno.

 

[tw99]

Interesting. I've noticed mine making that little pop on acceleration recently, and wondered if it was the shiftcam.

 

[GSMarky]

Wow - interesting read thank you.

I have a re-mapped ECU and a baffle less Akra' & the QS pops when short shifting out of bends with a good amount of throttle on is one of the joys of this 1250 GSA. It'll pop in a similar way on the downshifts too.

Now I hadn't even considered the link to the shift cam & for sure it is a totally seamless changeover.

Gotta give it to the very clever engineers @ BMW!!

When I almost moved to the 1300 the lack of audio from the motor was a concern..

 

[JoeBiff]

…..the first bit of the vid shows what happens when going uphill in the higher gears or overtaking when you open the throttle, the middle bit is on a light throttle in third gear but letting the engine rev out - shiftcam only switches when at 5k and the last part of the vid shows shiftcam operating when squirting out of a slow corner when it operates at about 3k.

Could you film a short vid when you slow down approaching a hairpin bend, then downshift (say from third to second) before the bend and tight uphill, and then note the increase in revs due to the down change as you enter and negotiate the hairpin.
I’d be interested to see what the shiftcam does from, say, 1500 in third, to second gear as more load comes on to the engine as the hill gradient steepens.

 

[G&T]

It’s clever, that’s all I know. Never feel a thing

Thanks for the investigation.

 

[landmarkjohn]

Awesome. Seriously. And I'm only half way through..

 

[Hartley]

My 1250 GS from new had a little pop at around 4200 , my GSA is exactly the same.
In fact, one of the things I noticed when I felt something wasn’t right on my GS after new casing was the pop was gone,occasionally I’d hear something but no consistency on when and if. Once they’d eventually sorted it ( though never an outright admission something wasn’t right ) the pop returned.

I assumed it was something related to timing of shiftcam?

 

[Pukmeister]

Interesting stuff, I was suspicious that the shift cam was operating differently to the basic explanation BMW provide, but being seamless it was impossible to tell for sure.

Your gadget would seem to confirm this.......Well done

 

[Hann]

Whilst out this morning i made another thrilling video of the Shiftcam in action (green LED lo, red LED hi lift) which is hopefully a bit clearer than the first vid i did above.
To recap, any time you open the throttle over about one third - regardless of engine speed, the shiftcam operates, even at idle when `blipping` the throttle, see vid.
You could ride all day in a moderately brisk fashion without shiftcam switching if you were just bimbling about.
Banging up through the gears with quickshifter it`s on the hi lift lobes all the time.
On the level (motorway) it`ll be on permanently only when you`ve gone over the NSL by quite a few mph..
If you extend the engine speed on a light throttle it only switches once engine speed reaches 5K - see vid.
It`s constantly switching and is imperceptable in operation.

 

[snerkler]

Interesting read. My understanding is the ECU controls the shift cam depending on throttle opening, load, gear, revs etc etc.

If I’m honest I’m not a huge fan of the ‘pop’ when it shifts, but it doesn’t bother too me much either. I’ve got the akro can and I don’t know if it’s more noticeable on that than the stock can