Hi Christian,
Das Rallye-Zwitschern kriegen wir sowieso nicht hin => da fehlt die Hardware...
Die meisten BOVs produzieren eher ein Zischen (lautmalerisch "Whooosh")...
Was das Phaenomen "Compressor Surge" angeht: wenn das Geraeusch unter WOT = Volllast auftritt, dann ist es in der Tat sehr schaedlich fuer unser Geblaese... da muss das BOV dann neu justiert werden... aber wenn es bei LD < 0,4 auftritt (also Teillast), dann ist es kein Problem. Die Aussage habe ich von Mr GOFASTBITS persoenlich - steht aber auch in ihren FAQ:
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1:
How do you get a BOV to make the fluttering, chirping kind of noise?
This noise is actually compressor surge, and it does not come from the BOV, but from the intake of the turbo. Compressor surge is basically a situation where boosted air forces its way back through the compressor housing when the throttle is closed, causing that noise as the blades of the compressor "slip" in the air. Although many people like the sound of compressor surge, it can shorten the life of the turbo depending on its severity. The pulsing air in the inlet can cause excess thrust loads on the bearings, and also shock loads on the compressor blades.
It is best to set the valve spring pressure to avoid this noise, but for those that like it, it is possible to set the spring pressure a bit tighter to get the noise at lower RPM, whilst still allowing the valve to blow off properly at high RPM. The speed of the turbo and the forces it endures rise a lot with RPM, so low in the rev range you can get away with it without placing too much extra load on the turbo.
2.
Blow-off valve myth #2: The fluttering sound is usually believed to be the blow-off valve. In reality, it is caused by a blow-off valve, but does not come from the blow-off valve. If the spring pre-load is adjusted too tight, this will cause compressor surge, which as described above is the sound of air exiting the turbo.
Compressor surge: You can think of surge as the point at which the compressor blades begin to "slip" in the air, losing their pumping ability, much like an aircraft wing loses its lift when it stalls. In a turbo, this happens in a series of bursts, as the blades slip, then bite, slip then bite. This sets up a pulsing wave in the turbo piping and explains why the sound has that characteristic "flutter".
The interesting thing about compressor surge is that it occurs much more readily at low turbo shaft speeds. At these low shaft speeds, on road cars this is generally between 2000 and 3000 RPM, compressor surge is not much of a problem, as the loads generated by the surge are miniscule compared to what the turbo encounters at high boost. However, if surge occurs at high RPM and boost, it is possible to reduce the turbo life and/or damage the compressor.
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OT: Stichwort "sounds":
http://www.gofastbits.com/index.php?parentid=sounds&option=sounds
Gruss,
Jan
the boost is strong in my family. my car has it, my club has it...and my friends...yes,it's you - you've got it,too 
STi... 
.
Freitag, 3. Mai 2024, 11:23
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