| Right, so your BOVs would have the same ability to vent pressure as say, your throttle bodies, due to the location. Is this an accurate assumption? You mention this a few times, but it has been my impression that the flow capacity of a BOV is less than that of a throttle body? If they are indeed similar then I can see your reasoning (specifically for this application with such a relatively short intake tract). At some point, you reach the point of a negligible differential.
I agree with this completely, at some point the distance and associated restrictions will become significant you'll find there's a limit to how far you can separate the vent from the source. Furthemore the closer to the TB, the less gas reversion and kinetic energy to overcome once you reopen the TB.
This is a valid question/point, however I question whether the influence is as significant as you suggest. Note that the TB's are not completely blocked and air is still flowing in that direction. Furthermore, we're looking only to create a pressure drop, not necessarily evacuate all of the pressurized air. Only the air in close vicinity to the vent would experience the flow reversal. And finally the kinetic energy and momentum of air shouldn't be that significant at this location in the intake tract. The velocity and turbulence is far below that experienced within the compressor itself. If the medium was water instead of air, then I could certainly see the motivation to place the vent at the area of blockage (TB). If the turbo doesn't experience compressor surge from a high pressure gradient while it's feeding the engine, it won't experience it from a BOV venting in the same location.
Compressor surge isn't what I was trying to prevent, it's turbo "bark" or rapid reversal of the compressor. This is due to a rapid drop in drive pressure at the turbine while the compressor is at a higher pressure. This stalls or backdrives the compressor which of course is not good for the turbo. IMO the closing of the TB is a critical event, but moreso because of the associated drop in turbine drive pressure than it's function as a blockage for the intake flow. You're leaving out a few variables.
I think we both are, and I suspect it's all for naught anyway. In this specific application I suspect either location will perform equally well, or at least with negligible difference (whichever way proves most efficient). Has anyone tried swapping from one location to another? If so was the change significant? As you mentioned, with all of the associated variables I'd favor empirical results over theory. Ash's point about the heatsoak is another I didn't even know about, so that should be considered as well.
I agree, and I wasn't aware of that behavior either. Interesting stuff :)
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NA to TT, starting from the ground up... |
