Subject	Noob question about boost/vacuum
Posted by	FuerGrissa on May 29, 2008 at 10:59 PM
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Message	I hope I don't get flamed for asking this, it's not really a mechanical question but more just to help me understand. To preface the question when you get into the throttle on a forced induction car (like our z's obviously) the boost/vacuum guage starts to read positive pressure on the intake system. This is easy to understand because the turbo's compressor is jamming in extra air to the system, however when you are out of the throttle the guage reads negative pressure, or vacuum on the system. This is what confuses me. If you are not forcing in any air to the system than at the very least, shouldn't there be 0 pressure rather than negative (vacuum pressure)? to say that the system is no longer under posotive pressure and is now under negative preassure to me implies that something is sucking air backwards out of the intake system. Can someone please enlighten me as to what is going on here?
Follow Ups	Noob question about boost/vacuum - FuerGrissa 22:59:36 05/29/08 vacuum is suction through the intake manifold. - robo (sebring1970) 23:29:27 05/29/08 It's a matter of how much air the pistons are sucking in, - zellamay 10:33:31 05/30/08 Is 0 really the balance point? - Turd Furguson 12:22:35 05/30/08 There is always vaccum in front of the turbos, but I don't - zellamay 13:57:18 05/30/08 You hit it on the head pretty well - Broke_as_**** 15:15:27 05/30/08
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