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Yes, back into the turbo compressor inlet, it just gives the pressurised air an alternate path when the throttle is closed.
Ah, thanks! 👍
I'm sure if I'd ever actually looked at the plumbing on a modern turbo, I'd have noticed it.
Lol not sure if all that's sunk in yet, but yes i think you are correct, the closing throttle is the source of the "pressure pulse" and the BOV vent's into the compressor side of the turbo not the intake. Some air will leak out the intake depending on how long the throttle is closed for I'd imagine.
I was hesitant to use the term compressor surge, as I've heard it being used before to describe what I'm talking about, but was never sure weather it's the right term or not.
I'm no expert just use my own terms to describe things.
I never really noticed much turbo sounds in GT5, I use "bumper cam" and would have thought i would of heard them more clearly.
Thanks for your input on this, it definitely helped! I though I was going mad, I was sure I'd seen "compressor surge" somewhere...
I've just spent a wee while trying to weed out the definitions of things. It turns out that there is a tendency to use different terms to mean the same thing, and the same term for different things.
Anyway, apparently "
surge" is what happens to the compressor wheel - it's any change in its acceleration (rotation rate), which is basically happening all the time as it scoops up fresh fluid and when it chucks a "slug" of compressed fluid off the vane out the other end. If this gets to a high level, it will start to knacker bearings and fatigue the compressor wheel. Good mechanical and aerodynamic design of the compressor can minimise this kind of "surge".
On top of that, any sudden change in the speed of the discharged fluid will cause a pressure wave. Change the throttle position, or suddenly change the compressor speed etc. and it will start a pressure wave. On a turbo car, this reverberates between the throttle and the compressor, causing a change in the acceleration in the compressor wheel - it causes it to "surge" / "jerk" / "jolt" / "lurch" more. Add to that the potentially destructive nature of these acoustic waves, and you can see why its big business trying to prevent them in industrial kit, especially for liquids. I don't think they bother with this on road cars, given that air is compressible. Expansion tanks in the flow-line, anyone?
Finally, "compressor surge" is a slightly different animal. It was a big problem in jet engines for a while - although they call it "stall", as may be more appropriate there. Anyway,
Wikipedia knows what it is. So, on a turbo-charged car, shutting the throttle off means the discharge pressure builds to a point that the compressor can't maintain the pressure ratio (discharge / inlet), so reverse flow occurs
whilst the compressor is still turning - but, all that energy has to go somewhere, so it gets hot and slows down. Now I can see why venting to the inlet is preferable.
That probably clarifies nothing, but I enjoyed wasting my time on it.
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I use bumper cam, too; I'm using the stereo mix and almost never hear the turbo sound effects. I suppose they're still struggling to find the middle-ground after
GT2!