Just to clear this up one LAST time, here's what Garrett say on the subject:
http://www.turbobygarrett.com/turbob...r/faqs.html#t3
Quote:
What is compressor surge?
The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side.
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself.
Common conditions that result in compressor surge on turbocharger gasoline engines are:
- A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
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So - we've established NOT running a dump valve causes surge or compressor stall (dictated by the amount of pressure built up in the intake system).
Given that...
Quote:
What is Turbo Lag?
Turbo lag is the time delay of boost response after the throttle is opened when operating above the boost threshold engine speed. Turbo lag is determined by many factors, including turbo size relative to engine size, the state of tuning of the engine, the inertia of the turbo's rotating group, turbine efficiency, intake plumbing losses, exhaust backpressure, etc.
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So - we can see a direct correlation between the compressor stalling and lag.
Is that clear enough?