Well without going into all the details (mainly because I don't know all the details)
Bark is a condition that happens when the turbo gets way outside it performance curve, kinda like a compressor stall on an airplane. This can happen when the power output of the motor instantly changes. for example I have barked my turbo doing a brake stand and then instantly take my foot out of the throttle, the waste gate can't dump all that air all at once and a pressure wave builds up in the turbo and kinda farts back through the system against the incoming air.
I have also heard of certian performance boxes causing a bark, this seems to be caused by pushing the turbo too far outside the range of how much air it can pump. It starts to fight itself. These pressure waves in the turbo are very bad for the unit in the long run......this is not something you should do everyday.
I'm sure someone has a better explination of this but I thought I would give it a try anyway.
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