spawn

if you just notice your vacuum line to your dump/blow off valve broke?
i'm running a arp chip w/ tt valve
broke for a couple of months i think

birdsong

Blow out the turbo. But if it's still working, heh.

Ram@S4-MTM

What do they do?


A dump valve operates simply in two ways; throttle open, and throttle closed. When the throttle is open, the boost pressure coming into the valve from below the diaphragm/piston is equalled by the pressure onto the top of the diaphragm/piston that comes via the small hose from the engine manifold vacuum.


As the pressures are equal, the spring holds the diaphragm/piston onto its seat, and prevents the pressure venting away. When the throttle is closed, the pressure coming into the top of the valve is significantly reduced, (often to a vacuum), and the pressure below the diaphram lifts it away from its seat, allowing the excess pressure to vent away.


When the throttle is reopened, the pressures again equalise, the spring pushes the diaphragm onto its seat, and the boost pressure cannot vent away.


Why are they there?


Dump Valves are fitted for a number of reasons. Without a dump valve, when the throttle was closed, the build up of boost pressure would be immense, very similar to closing a quickly flowing water tap.


This excessive pressure, would put the components of the system under adverse strain. More significantly, it can put a large strain on the turbocharger itself, firstly stalling the compressor shaft, then trying to force the compressor wheel out of the turbo, against its bearings. So, the dump valve simply prevents mechanical damage to the turbo and its pipe work, prolongs turbocharger life, and prevents excessive turbo - lag that would be caused by the compressor shaft stalling.