I know this thread started in 2016; can those who have knowledge of the current Bosch internal workings update us for the Drive Units of today?
It's my understanding that there are 2 software versions for each unit, one for IGHs and one for derailleurs.
As I understand it, the IGH version just senses torque at all crank positions, and expects to find rider input lowest when the pedals are at the 12 and 6 o'clock positions. It makes the electric torque assist track these variations, and suggests that IGH riders chage gear at these positions, because the total torque the IGH sees will be lowest at these crank positions.
The derailleur version is (as described in these posts in 2016) sensing the variations in total output torque from the drive Unit, and interpreting a torque dip as a shift to a higher gear (smaller sprocket) when the chain comes off the last teeth of the larger sprocket, and decides it should soften the reapplication of output torque to inclrease chain life.
Similarly, I believe that a torque output spike upwards will be sensed as a downshift happening, when the chain starts transmitting torque through the larger sprocket.
I am having issues right now with a Gazelle C380+ which has the Enviolo hub and the Performance Speed Gen4 DU with the 29mph assist cutoff. Whenever I am in one of the assist modes, and I stop pedalling, the electric assis persists for between a quarter and a third of a second.
This a problem when I need to downshift while climbing a hill, because the Enviolo hub is unable to shift under the load put on it while in Tour, Sport or Turbo assist modes. It is not keen to do it in Eco either, and in Off mode it is also reluctant to shift under load, and is much much more willing if you briefly stop pedalling. This is quite normal for these types of transmission; when drive is being transmitted by metal pressing against metal, and shifting ratios depends on metal slipping over metal, the efforts to make the drive be transmitted act against efforts to change ratios.
It is true that the 2021 Enviolo documentation says that rtios may be changed, even under load, but this is a complete fiction in the mind of their marketing people, especially if the bike is an ebike.
This hub is different from the Shimano or Sturmey Archer types in that those IGHs use the shifter mechanism as a sort of gear shift request, or a pre-selector system. The new desired gear is pre-selected by tensioning or compressing a spring, but the gearset doing the driving does not change until load is reduced, and then the path of the drive through the hub changes.
With the Enviolo hub, the manual shifter is connected directly to the angle of the rotating balls which transmit the drive torque, and until the axis of the balls move, the ration doesn't change. And they won't move until load is reduced, and reduced by a lot if electric assist is being used.
Now this inability to rotate the axis of the drive balls while under load may well be a facet of the pull-pull manual select system. If you try to move the control whiile under load, you will put the cable out of adjustment by overpowering it. This is explained by the manual, by the LBS and procedures are published to restore the manual selector to normal operation, although this is not simple, and ends with the caveat that if it doesn't work, take it to your LBS. This happened to me once, and it took a while to get it working again, but I did manage it.
So now I always stop pedalling whenever I shift. I actually put just enough force on the shifter that it would move if I wasn't pedalling, it would move. Then I stop pedalling and it instantly moves. Or it would instantly move if I was in Off mode because evidently Bosch believes that the Enviolo can be shifted under load, and so it's just fine in they keep the power on for a third of a second after I stop pedalling. If I was trying to climb a hill of 8% at say 85rpm of cadence, then by the time I've got a lower gear engaged, I better have guessed right how far to move the shifter, because I'll probably have slowed down much more than I wanted by not pedalling, and I may have to go and do it all again.
So I'm talking to Gazelle about this, and they are talking to their Bosch rep, who wants to see which software version I have (derailleur or IGH) and swap me to the other one. All of this can only be done at my Gazelle dealer, and that's not such a great thing for me.
And I don't think it will work, because I don't think they understand yet that the problem is with moving the shift control while this extra delay in removing assist is in progress. I think they are going to need to properly evaluate the Enviolo hub at Bosch ans stop believing the marketing crap.
So if any of you have an enviolo and some hills, I'd like to know if you are also experiencing this.
Just in the past few days however, I have stumbled upon a workaround. I already stop pedalling when I shift, but Bosch sobotages that when assist is in effect. Howver if I put a little force on the shifter as described above, then stop pedalling at the 3 and 9 o'clock pedal positions, and immediately back pedal to the 6 and 12 o'clock pedal positions, then I don't get this sabotaging delay; the electric assist goes to zero immediately.
Evidently Bosch evaluates application of assist by pedalling detection (as we know) but prioritizes "no assist when back pedalling" over "delay the assist cutoff. At least I can live with this, but it's a pretty ugly situation, and it is making the bike much less fun to ride.
