aftermarket dump valve

[signumturbo04]

after fitting an aftermarket dump vale and a blanking plate i bought from ebay my car seems to hold boost alot longer than it used to and also the lag when changing gear has dissapeared too is this right or have i fitted it wrong? meant to say engine is z20net and the dump valve is adjustable, currently adjusted to half way between hard and soft.

[Danwells72]

Dont know about holding the boost longer but i guess due to the different piping thats possible. WIth regard to spooling, yes you will see a decrease in the lag as when the throttle is released the butterfly valve closes holding the pressure in the pipes and in return sending it back to the turbo, with the dump valve it will release this pressure build up resulting in no back pressure.

EDIT: unless your a big fan of the pppssssttt, i would suggest a recirculating valve as oppose to an atmospheric valve

[signumturbo04]

what difference does a recirculating dump valve have over an atmospheric type?

[Jezzy]

Dont know about holding the boost longer but i guess due to the different piping thats possible. WIth regard to spooling, yes you will see a decrease in the lag as when the throttle is released the butterfly valve closes holding the pressure in the pipes and in return sending it back to the turbo, with the dump valve it will release this pressure build up resulting in no back pressure.

EDIT: unless your a big fan of the pppssssttt, i would suggest a recirculating valve as oppose to an atmospheric valve

I (respectfully) disagree with that - the Z20NET already has a turbo bypass valve - when the throttle is released, instead of the boost slowing the turbo (standard engine) or the boost being released (dump valve fitted), on the NET the boost is allowed to bypass the engine but still allow the turbo to freewheel - when the throttle is opened again the turbo is already spinning fast enough to produce more boost.