yes & no,
Please bear with me so i can explain
on a petrol turbo a dump valve is used as there is a throttle butterfly to contend with, so basically when you accell hard & then snap the throttle shut to change gear there is a big boost increase that cant go anywhere as the throttle butterfly is shut & the turbo is trying to push the "boost" through the pipework into the engine but cant as the throttle butterfly is there in the way, thsi can cause the turbo to stall, shatter the compressor wheel,burst the intercooler etc & worst case scenario in cars running 2 bar+ of boost, bend the throttle butterfly,
so by fitting a dumpvalve it "dumps" the above pressure to atmosphere using the vacum created when the throttle is shut to pull open the dump valve (tish on scoobys etc) or recircs it back into the inlet manifold ( most VAG cars & vauxhalls have to be done this way as the ecu throws a wobbly wondering where the air has gone that it measerd on the way in if fitted with an atmosheric dump valve) & then life is good, next gear change please,
on a diesel turbo engine, it doesnt have a throttle butterfly ( well none of the LR diesels do (tdi/ Td5)) so there isnt any need to fit a dump valve to a diesel, it simply creates noise, also to activate a DV on a diesel it needs to have a vacum that can be switched, so requires a switch on the fuel pump to activate the solenoid for the vacum when the throttle is shut, which thens pulls a vacum on the dv to make it open,
