DSG shift is not instantly release offgoing clutch and ramp incoming to max, they are both applied simultaneously, ongoing is faded in, offgoing is faded out.
At fast-torque-handover (schnelle Überschneidung), DCT will.
Only in normal torque-handover both clutches simultanous fade.These are two differend "normal" modes of torque-handover.
If offgoing clutch is still dragging at that point (überschneidung), then without torque reduction it will not shift until the offgoing clutch is fully released, there is not enough pressure physically on ongoing to fight offgoing + overcome engine max tq, especially if it is high.
Not, there is NO torque-intervention during torque-handover. Torque-intervention is only in synchronisation activ.
The shift itself is allready completed, when torque-handover is done and the ongoing clutch will carry the engine torque.
I think you are now mismatch "shifting" though the differnd phases of a shift process.
When ongoing clutch will takeover the complete engine torque, clutch is still slipping.
To stop now slipping, you can overshoot the clutch or decrease engine torque by request.
But this is synchronisation, the last phase of "shifting"
Of cause there is enough pressure for ongoing clutch to fight against offgoing.
Is status is called "bracing", because is braces both shafts to eatch other.
You can feel or measure it when decreasing vehicle acceleration during torque-handover.
The goal is, not to brace the gearbox during torque-handover and have a smoose torque-handover.
Just calculate the summe of offgoing- and ongoing clutch during torque-handover and you will see how often summe of clutch capacities is higher the engine torque. In this case you are bracing the gearbox and decrease engine speed because, engine torque is lower then torque of the two clutches.
Your pump is making a certain amount of pressure, even if the solenoid valve is fully open you can never ever exceed the base pressure.
Right, but the complete base pressure is not used at the clutch for torqueflow and maxium allowed input torque. So you have still a amound of pressue to "overshoot" the clutch.
Just exactly for shoot the clutch (or overshoot) when torque decrease is not taken over by ECU and DCT will forced decrease engine speed to actual shaft speed.
This is level2 security of DCT and a MUST by FUSI.
So no, no shift will happen until the first clutch is fully released!
Defintion of "shift" is this case is incorrect. Synchronisation will not start until torque-handover is not finished. This is correct.
At this point this is not anymore normal shift progress and the DSG at least on VAG will usually go into limp mode. What you are describing is extreme edge case, it's not relevant here.
Not true:
to shoot clutch will allways happend the engine speed decrease is too low or engine is not synchron is allowed synchron time.
This is normal behaviour of DCT and will not give any DTC or limp home.
Every Engine-Powered-Upshift (Zwischengas-Rückschaltung) will end with a overshoot of clutch at DQ250/DQ381/DQ500 and others too
Also shiftmode "AMax" or "fast-torque-handover" (minimal overall shift time, used e.g. at speedlimiter or AMax detection) will just instand open offgoing clutch and parallel overshoot ongoing clutch to use inertior energy of engine to increase acceleration during shift.
Short summery of this discussion:
overshooting clutches is allways used at DCT, when engine speed will not synchronice to shaft speed and engine-torque-decrease-request is not enough or is not take over by ECU.
So:
it is possible to upshift without torque-interventions.
That meens that a manual ECU, witch does not care about gearbox interventions
will also work, but you will have a lot vibrations and bad shifting.But at the end, it will work!
Of cause, it is no goal to run a vehicle like this, but ones a gain it is possible by DCT.
Now we can go back to the problem of the topic