| The turbo is supplying the air flow, not the throttle bodies, and there is a pressure drop between the turbo and the throttle bodies due to the length of the intake tract and the presence of the intercoolers. By placing the BOV's near the TB you're placing it in the area with the lowest pressure and farthest from the area of real interest. The pressure you really want to alleviate is the high pressure right at the compressor outlet of the turbo. By placing the BOV close to the turbo you eliminate the intercoolers and the rest of the intercooler piping (ie. restrictions) from the flow path to relieve the pressure. Right, so your BOVs would have the same ability to vent pressure as say, your throttle bodies, due to the location. In other words, the farther you place the BOV from the compressor outlet the greater the restriction and the slower the release of pressure. By doing this your are, in essence, placing a restriction in your BOV. The same restriction that the throttle bodies have for consuming air. Think of it this way, if your intake tract was 100 yards long would you still place the BOV 100 yards away from the compressor outlet? For the sake of your turbo, I would hope not. The intake tract is not 100 yards long. At some point, you reach the point of a negligible differential. The BOVs vent pressure just as easily as the TBs. Furthemore the closer to the TB, the less gas reversion and kinetic energy to overcome once you reopen the 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. The BOV should be located as close to the compressor outlet as reasonably possible. The real question is this, is the effective restriction between the compressor outlet and TB of any real significance or is it negligible? After all we don't have 100 yards worth of restriction, it's only a few feet. I don't know the answer to this :shrug: Closer to the BOV is "ideal", but in this particular application the difference between inner and outer pipes may in fact be negligible. Closer to the TB is not the "ideal" location however, that much is clear. Not really. You've now got intake gas reversion kinetic energy to overcome upon reopening of the throttle. Not to mention the fact that the BOVs can vent the system pressure just as well as the TBs can consume it. You're leaving out a few variables. Ash's point about the heatsoak is another I didn't even know about, so that should be considered as well. For a drag racer, or street driven Z, it's probably not even an issue. On the track, that could cause a measureable difference I believe.
Recursively Yours,
Kenny...
PETZ Member #5
SteamyZ. Never had did me wrong. - SL103 07/06/04 11:58:15
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