overboost!

[imp124]

after some clutch poblems i took the ST down the road where coming back the turbo boost kicked in spools very quickly and goes way past 1 bar, where i quickly stopped.

i do not have a boost controller attatched just the pipe from the nipple on the turbo exit to the actuator under the turbo. could this be stuck closed mabe?

 

[Baz]

Check the pipe isnt block and the actuato isnt jammed also recheck all your vac lines(Y)

 

[imp124]

will check the actuator pipe, it looked ok but i will take it off and look at the actuator too, scary stuff though :\

 

[Duncan]

yeah most likely a big vacuum leak between the wastegate actuator line and the plenum. It only overboosts with the turbo right?

BTW mine was running 15psi (1bar+) fine, nothing to worry about if that is what you were aiming for....

 

[imp124]

i am looking at any leaks, split pipes etc and will update as i find them, looking for stock boost as there is no controller piped into the turbo (yes overboost on turbo by the way)

 

[imp124]

had a look cannot see anything plainly obvious, i did put exactly 1bar pressure down the actuator pipe and the actuator opens and closes as it should it appears. i had another brief drive in daylight, it appears that when the revs are high and the changeover from s/c to turbo is small the overboost does not happen but if i put it in a high gear at low revs it overboosts to about 1.4 bar to where i immediately let off the accelerator. It feels that it could be something to do with the bypass valve as i cannout hear it woosh open at low revs where i can if i floor it if you know what i mean? i have taken one pipe off the bypass valve when the car was not running (the pipe that runs across the top of the rockercover on the metal rail. and there was a lot of vacuum in this pipe still is this normal?

help would be appreciated

cheers

Steve

 

[Baz]

had a look cannot see anything plainly obvious, i did put exactly 1bar pressure down the actuator pipe and the actuator opens and closes as it should it appears. i had another brief drive in daylight, it appears that when the revs are high and the changeover from s/c to turbo is small the overboost does not happen but if i put it in a high gear at low revs it overboosts to about 1.4 bar to where i immediately let off the accelerator. It feels that it could be something to do with the bypass valve as i cannout hear it woosh open at low revs where i can if i floor it if you know what i mean? i have taken one pipe off the bypass valve when the car was not running (the pipe that runs across the top of the rockercover on the metal rail. and there was a lot of vacuum in this pipe still is this normal?

help would be appreciated

cheers

Steve

The vacuum thing is normal but it sounds like a pipe was changed to give the over boost

 

[imp124]

humm, i havnt had many pipes off when i did the box conversion and boost seemed fine before this, will look again tomorrow

Steve