you have a too strong spring if:
you dont hear the dump air sound on part throttle acc. shifting gear. (it should dump both on low and high boost!)
you hear compressor stall sound when coming off the throttle, maybe only on part throttle acc. and/or low boost.
you hear more then one dump when coming off the throttle, it should be one dump only.
you have a too soft spring if:
you hear the dump on part throttle but still on the throttle.
you feel the DV dumps to quick when you dont lift the throttle so much. (N249 delete can also cure this)
i dont want to sound rude but i think alot of people forget how the DV works and why its needed.
diverter valves are used to prevent compressor surge and to minimize lag when shifting gear.
there are 2 sides on a normal diverter valve, infront of the piston is the turbo/boost side and on the rear of the piston is the control/vacuum side, there are only 2sides on a piston as it will only move 2ways, up/open down/close.
a scenario/example on how it works:
when engine idle you have atmospheric pressure on the turbo/boost side and something like -0,6bar pressure (vacuum) on the control/vacuum side.
this is 0,6bar force that tryes to push the piston open, its only the spring that controle if the piston is open or not here, lets say 0,8bar of force/pressure is needed to push it open, its a soft spring, right!?
now the engine is on full load, throttle to the floor and running 0,8bar of boost.
there is 0,8bar of boost on the turbo/boost side of the piston and 0,8bar of pressure on the control/vacuum side.
0,8 bar of pressure on both sides of the piston and this cancel each other out, so the spring dont see any force/pressure thats tryes to push it open.
how can this be, i said: 0,8bar of force/pressure is needed to push it open, its a soft spring, right!?
now what happends if the same setup is running 1,5bar of boost? its the same 1,5bar of pressure on both sides of the piston and this cancel each other out, so the spring dont see any force/pressure thats tryes to push it open.
now here is what people seems to forget: if the same setup have a diverter valve with a strong spring that can hold 1,5bar of pressure, how is it going to vent the air out of the system when the turbo pressure drops below 0,9bar of boost, remember -0,6bar of vacuum and the spring need 1,5bar to force it open = it will be closed at 0,9 bar of pressure, this is not the intention of the diverter valve.
a too strong spring is almost the same as having no diverter valve at all.
what I mean by that is, you dont need a strong spring to hold the boost when running full boost or throttle to the floor, the only time you need a strong spring is if you build up turbo pressure when on part throttle or cruising speed when you have less pressure on the control/vacuum side of the piston.
sorry for the long write up but i think people forget the downside of those strong springes.
