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Turbo Dump Valves

  Clio v6

Am I right in thinking these gadgets are what case that " bottle of coke opening" Pisssssst noise?

Is there a real use for these ie should my MPV ( 20 valve Turbo ) have one? Or does it have one as standard, but not just not connected to the car amp and PA sysstem for Seafront cruises?

Again your comments please.

Yes they do, but only if atmospheric type. You can get recirculating ones (that feed the air back into the system) which are as good as silent.

Yes they have a valid function. That being to release excess pressure in the turbo after throttle release. This does 2 main things: Firstly it can reduce turbo lag by letting the turbo carry on spinning (by releasing the pressure built up in it) thus giving a better response when going back on the throttle. Secondly they can increase the longevity of the turbo as there is less stress on it. A lot of pressure can build up within turbos and a dump valve reduces the stress on the fins, and can prolong life

But yes, they are mainly used for show by most people who have one that sounds like bus air brakes! A lot of people with them have no idea of what they are used for.

Modern turbo cars will have them as standard but in the recirculating type form - usually a plastic Bosch one. You can get all sorts for it though - Bailey dump valves have a good reputation - its what I used to have on my turbo (recirculating type though!)
  BMW 320d Sport

Mikes said it all I think. My turbo conversion comes with one as standard because they are important. Lets say youve got the turbo spinning on full boost at 100,000 rpm which isnt that fast for a turbo. You let off the accelerator to change gear, the throttle plate closes, suddenly all that boost between the turbo compressor and the throttle body, cant go anywhere except back through the rapidly spinning compressor. To avoid backing up the compressor and obviously straining it by huge sudden reversals of forces on it, the dump valve opens whenever there is boost in the circuit and the throttle closes, letting out unused boost pressure and letting the compressor wheel carry on spinning as before.