erratic boost
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Joined: Oct 2002
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erratic boost
Car:
'02 1.8T, GIAC, APR exhaust, Forge 007, APR snubmount, copper plugs
Story:
A few days ago, I started getting some pretty nasty surging through every gear, put the car up and find that the vac line had become disconnected from the 007 valve - mystery solved, right? Well, not quite; the car is no longer surging, but now I'm experiencing a general loss of power. The turbo seems to spool up fine (though not nearly as audible as it usually is), but the boost rarely comes. When it does, it all hits at around 4K - not the usual buildup from about 3.25-3.5K. I've also been smelling burnt oil at irregular intervals while driving (had the oil changed about 3k ago). I'm not throwing any CELs and there is no smoke coming out of the exhaust. The first thing to come to mind is a boost leak independent of a slow oil leak. Something must have happened as a result of the disconnected vac line, because the car was running fine in the same state weeks before (in terms of aftermarket hardware/software). Any thoughts or suggestions? I'll definitely be bringing it into the shop within the next few days, i'd just like to know if anyone has any insight.
'02 1.8T, GIAC, APR exhaust, Forge 007, APR snubmount, copper plugs
Story:
A few days ago, I started getting some pretty nasty surging through every gear, put the car up and find that the vac line had become disconnected from the 007 valve - mystery solved, right? Well, not quite; the car is no longer surging, but now I'm experiencing a general loss of power. The turbo seems to spool up fine (though not nearly as audible as it usually is), but the boost rarely comes. When it does, it all hits at around 4K - not the usual buildup from about 3.25-3.5K. I've also been smelling burnt oil at irregular intervals while driving (had the oil changed about 3k ago). I'm not throwing any CELs and there is no smoke coming out of the exhaust. The first thing to come to mind is a boost leak independent of a slow oil leak. Something must have happened as a result of the disconnected vac line, because the car was running fine in the same state weeks before (in terms of aftermarket hardware/software). Any thoughts or suggestions? I'll definitely be bringing it into the shop within the next few days, i'd just like to know if anyone has any insight.
AudiWorld Super User
Joined: Oct 2005
Posts: 6,127
Likes: 3
With the DV closed all the time, there is a chance that the compressor ....
impeller suffered some shock damage from "compressor surge", that is when compressed air, having no place to go, reverses flow in the compressor. That flow reversal will create sharp, high pressure spikes and shock to the compressor impeller. The turbo bearings can be damaged also. From what you describe regarding the boost behavior now, that is consistent with turbo damage. Inspect the compressor impeller and shaft bearings carefully.
AudiWorld Super User
Joined: Oct 2005
Posts: 6,127
Likes: 3
The turbo should be removed from the engine, then the compressor housing is removed.....
to allow inspection of the compressor impeller. You are looking for bent blades or missing pieces of broken blades. Bearing clearance is checked with a dial indicator set to measure the radial(side) play in the shaft bushings. There is a thrust bearing loaded axially also, so that should be checked. That is back and forth play along the shaft center line direction. You can get the specs by calling a Diesel Fuel Injection/Turbocharger repair shop that works with KKK/Borg Warner. or take the turbo to that shop and they can check it out and repair as necessary.
It is possible to view the compressor partially, by removing the inlet hose, but it won't permit complete visual access, particularly for the exducer(discharge) part of the impeller blades most subject to surge shock damage.
It is possible to view the compressor partially, by removing the inlet hose, but it won't permit complete visual access, particularly for the exducer(discharge) part of the impeller blades most subject to surge shock damage.
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