I'm curious why you think they exist and what they do?
Good question. My gut says the only reason they exist is because it would be a waste of aluminum if the casting were solid in that region.
Your suggestion that the slots exist to bleed off excess capacity during a sudden drop in engine demand (sort of a buffer) may or may not hold water.
1. Are those slots open in such a way that excess inlet capacity can be bled off? I don't think they are.
2. If the slots are closed, are they of large enough volume to act as a useful reservoir during a drop in demand at the compressor? Again, my gut says there are 2 problems with this.
2a. Their volume relative to the volume of the intake is too small to do any good as a reservoir. The intake tract itself is a far more effective reservoir for excess air, so there would be no need to cut these slots for that purpose.
2b. During normal operation those slots are already filled with air (I doubt the silencer ring is an effective seal). So during surge operation they're only going to get more air if the pressure in the intake rises (which it does). But the moment the intake pressure exceeds atmospheric pressure flow is simply going to back out the filter, as opposed to pressurizing the slots.
Obviously, we can't ignore Nick's experience that the lack of a silencer ring reduced turbo bark. But we must ask ourselves, why? Forrest, maybe you're right and the slots are acting as either bleed passages or reservoirs. Or, maybe they're even acting as some sort of stall mitigation device. I don't know.
We must remember that the slots lie well outside the compressor inlet, whose walls are smooth.
Ryan
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