[brassman.erdman]

hey guys. my lpt is sounding kinda funny..

when i accelerate from around 1900 rpms i can hear my turbo spool. its nice, except lately ive been hearing a chattering sound, almost like the compressor wheel is wobbling? or like its spooling up the wrong way?

ill try to get a video of what im talking about up soon. should i be able to hear anything but the Saab Whoosh?

also im pretty sure all of my engine mounts are gone, could that be a factor? i dont think so but you never know... or at leat i dont.

Thanks guys,
Dennis

 

[MR.SAAB]

well that chatter is actually your turbo trying to spin on the opposite direction:nono; this is due to the extra back pressure being applied. do you have a stock blow off valve? because that seems like the culprit here. maybe a manual boost controller?

 

[brassman.erdman]

everything is its 15 yr old original part. i wanted to change computers and add the APC. should i add the bosch recirc valve to my update wishlist?

 

[MR.SAAB]

well if you are good with your hands id take apart the one you have now check out the spring and stuff. thats just what i would do

 

[brassman.erdman]

http://www.youtube.com/watch?v=48fQ6n61cD4

its on application of teh throttle. it only happens when the engine is cold.

it tried it last night and with some residual heat i could not find the noise.
after school today seemed to work.

is the sound off the throttle what you are referring to MR.SAAB?

 

[MR.SAAB]

http://www.youtube.com/watch?v=cPZZvd55hxg

as long as it doesnt do it every time you let off the gas then i wouldnt worry about it. mine does that as well. both my 9-3 and 9000 do it when it is cold out

 

[brassman.erdman]

it always does that... lsiten to the application of throttle. the spool sounds choppy.

the third time sounds the best, after the turn and second speed bump

if the after sound is bad, then i have another problem:roll:

 

[Superaero]

Back pressure in the exhaust cannot make the turbo try to reverse. The pressure upstream of the turbo is always higher than downstream.

The "blow off valve" has nothing to do with back pressure as that is on the intake side and releases compressed air pressure.

It is possible for the compressor wheel to be hit by pressure waves from the throttle plate closing if the blow off valve is defective and sticking closed but these usually fail open.

 

[drbolaget]

Check that all the nuts from the manifold to the turbo (x4) and from the turbo to the exhaust downpipe (x3) are tight. If they are fine, I'd swap in a new blow off valve.