wedge07

firstly engine is efi 1600cvh, t3 hybrid and -31 actuator and 14psi is what im running.
ill try and explain this but its hard but here goes lol
when i start her up and drive about shes mint and i get a nice loud PTSSSST from dump valve and boosts lovely.
if i turn her off say to nip in supermarket, or fill up fuel etc, when i turn her back on, she has this stupid annoying thing she does on boost, as soon as i start boosting, the turbo makes a really loud SSSSHHHH noise and itstead of the dumpvalve releasing when i change gear, the SSSHHHH noise just stops until im boosting again.(still boosts but not as powerful)
it does this upto 12psi, but if i hold the boost at 12psi for a few seconds, it suddenly boost to14psi and boosts like normal from 1-14psi and get my PPTTSSSSSTT from dumpvalve and shes mint until the next time i turn her off, then same all over again until i hold boost at 12psi etc????
if i park her up over night and go out init the next day shes fine until i turn her off again???? what the hells going on, driving me mad.
sorry for crap description, thats the only way i can explain it haha

cheers

luke19790_3

bin the shitvalve?

studabear

Sounds like the dump valve is playing up, replace or remove to confirm

wedge07

never thought dv, ill black it off n see then cheers guys

Stolton

I agree try removing the Dumpvalve they usally give up after a while..

wedge07

but if i remove dv wont my turbo backspin instead of dumping?? any gain on removing dv??

zvh

yes the possibility of massive air leaks !! a silly noise , and compressor stall on a t3 or t34 is minimal !! unless ur running a t88 turbo and 60 psi of boost there pointless end off

botters

iTrader: (2)

sticking dumpvalve, most can be rebuilt and or lubricated

Chopshop85

iTrader: (4)

Mine did the same and it was the dv. Had a bailey one, took it to them and said what was happening and they replaced it for free

Rob_DOHC

iTrader: (4)

Has it only just started doing this mate?

wedge07

a few months now rob, was fine before. took dv off n its still does it but with a loud squeeling noise and will only boost to 10psi and feels like ive lost quite a bit of power? put dv back on and it was still squeeling with back spin like i had no dv until i turned off n on and booted it past 12psi? any ideaa?

Rob_DOHC

iTrader: (4)

Perhaps a big boost leak? Do you have an AFR gauge?

Rob,

wedge07

if a big boost leak, it wouldnt boost sometimes would it? its like its only when it gets hot? yes have an afr gauge but its only off map sensor ill be getting a propper setup soon

Rob_DOHC

iTrader: (4)

Weird.... What are the afr's like when this is happening? And if you drive for a few miles does it improve?

wedge07

it sits just on rich, and is up and down on rev counter, tbh i dont pay attention to it as i dont think its right anyways. lol

dean richardson

Mine did this turned out to be the turbo had packed up . Would build up pressure but got no boost and a noise like it was blowing or sucking air in so stripped the turbo and the bearings had gone

wedge07

it boosts mint though sometimes, its only done it since i reshelled it, so im thinking maybe something ive done?

wedge07

just been out init, and it was back spinning like i had dv blanked off? give it full boost and dv dumped like it should? is dv fooked?

zvh

there just more hasstle than there worth bin the dumpvalve would be my advice m8

zvh

u could put a vaccy pump on the actuator and test the actuator too

wedge07

how do i do that mate, whats a vaccy pump?

wedge07

since i took dv off, cleaned it up and greased diaphram up (as it was jammed in) the dv is working brill now and boost problem is no longer an issue?how can a dv of caused this? a boost leak maybe????

Chopshop85

iTrader: (4)

If the DV isn't sealing complete I should think the hissing noise will be air being let out through the DV, like a small air leak.

I had a dodgy twin piston DV on mine and it would not completely close straight away. You would come on boost and it would hiss for a second or two, then the dv would close and the car would start pulling.

wedge07

yeah exactly what mine was doing apart from it would only start pulling if i held it at 12 psi. its mint now