ive heard they do not increase performance but many people have them.

 

They go whooooooooooooooooooooosh when you change gear....up or down.

Hope this helps.

 

does a standard scooby have them?

 

Yep, your standard scooby turbo has a recirculating dump valve as opposed to an "atmospheric" which gives you the "whooooshhhh" noise. They are designed to relieve back pressure on the turbo following gear change etc. After the turbo has compressed the air into the engine ie boost then this pressure has no where to go when the engine revs drop off during gear change. The effect without a dump valve would be to stall the turbo and in some cases this stall can shatter the main turbo shaft under high boost due to the forces exerted.

Hope this helps.

 

Thanks superflyguy
always wondered that

 

thanks for that

one more Q

does it effect petrol consumtion

one when whoooooosh past me and it stank of petrol was it waste petrol

 

The dump valve relieves the boost pressure before the fuel injectors have squirted fuel into the engine cylinders and therefore cant affect fuel consumption in that respect. The air released by a dumper shouldnt contain any fuel vapours or smell, this would be a time bomb if you consider the potential temperatures under the bonnet!!!

I read somewhere that the ecu can be "fooled" by an atmospheric dump valve as it assumes the air compressed has been used (not vented away) and therefore adds the relevant amount of fuel.....thus slightly overfuelling???? I have no noticable problem at all with this on mine though (MY97). Check your insurance before fitting them though guys....