Quote:
Originally Posted by ninjakafi_81
That sound would be called turbo barking or as some people like to call it " back firing ". I'm actually not to sure what exactly causes it but I've noticed when the operator lets go of the accelerator pedal is when you'd hear such noise.
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As you drop RPMs of a turbocharged vehicle, the turbo slows down and consequently the maximum boost pressure it can maintain drops. If you drop rpms/slow the turbo down quickly enough, the engine is no longer using enough air to drop the pressure in the intake manifold as quickly as the max boost capacity of the turbo is dropping. When this happens, air temporarily flows backwards through the compressor side of the turbo, causing it to slow down even more or outright stall it. Engine makes a single revolution at idle, and the excessive back pressure from the exhaust hits the turbine side of the stalled turbo and rapidly makes it spin again. It’s the rapid pressure changes within the turbo that make the barking/womp womp noise. It will happen 2-5 times in a row until the intake manifold pressure is the same as ambient air pressure.
Needless to say, this is very hard on turbochargers, and is generally the result of engineering oversight and/or the vanes being stuck on a vgt turbo. Installing a waste gate, or a pressure equalizer between the intake and exhaust manifolds will prevent any one of the several factors that contribute to this problem.