Not quite Peter,
On a petrol when the throttle closes and it blocks off the intake in order to dump the air to avoid stalling the turbo you vent it off to atmosphere in a 'psst noise'
Our diesels dont ever get a closed throttle plate, so we dont need a dump valve. you can bodge one up electronically, but it actually looses performance as you need to get the boost pressure back again
the wastegate on our turbo's is actually integral to the hot side of the exhaust itself, they are driven by the actuator. When boost pressure on the cold side is reached they open up and divert the hot gas away from the exhuast turbine therefore restricting the rpms the turbo can spool and therefore hitting you boost limit.
As a combination of the wastegate and hot side of the housing is too small for the volume and flow of gas, we are now seeing the pressure building up.
I have also realised that if my single simple plate method doesn't work, then i am going to also need another actuator to drive the wastegate, unless i get one with summit integrated into it.
I had put in a bit about the run back from the station to the farm, but discretion being the better part of valour and all that i decided to not post it, just suffice to say: it shifts
