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      11-05-2008, 04:01 PM   #75
exdos
Second Lieutenant
 
Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

Posts: 206
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Quote:
Originally Posted by ace996 View Post
-well, yes, but in our case the rivers are sealed and they lead to a lake...they don't "t-off" with one another which would have a scavenging/venturi effect...I understand your point I just don't think that exact situation is happening in the box.
Take another look at Part 4 in the diagram of your air intake, the arrows certainly suggest that all the inlets from Parts 1,2 and 3 are directed towards the engine. To me that suggests that they "T-into" a single confluence, and NOT "t-off" each other, if you see the difference in my semantics. To me, "t-ing into" suggests coming together, whereas t-ing off" suggests splitting apart. Likewise the confluence of the ducts from Parts 1,2 and 3 do not meet in a "lake" (i.e. still water/air): when your engine is turning, air inside Part 4 will always be moving. When the throttle is at minimal opening and when there is positive ram pressure in the air intake system, this will be like sluice gates being rapidly shut to the flow of air towards the engine, which will result in a "damming" of the flow causing the air to overflow out of the system when the pressure at any of the three sources is exceeded.

If I owned you car, I would have had that intake in pieces by now, so that I knew for sure exactly how it functions. Can I suggest that you draw a little schematic diagram of the function of Parts 1-4 so that you can work out exactly how they all integrated into one single air-intake system in ALL scenarios.

Quote:
Originally Posted by ace996 View Post
If the pressure zone at that point is less than what is present inside the airbox(the pressure fed from the front two inlets), then air will come out of that vent.

That's not correct. If the engine is operating at less than 100% VE under WOT, then it will take air from whatever source it can get it, including the hood vent. Likewise, you will find that under WOT the pressure of the air inside the air-intake system will always be at a pressure which is below the pressure at the mouths of all three intakes, with or without ram pressure, because, after all, the engine is an air pump. May I suggest that you experiment with a domestic vacuum cleaner and a Magnehlic pressure gauge placed around and inside the tip of the hose to form a mental picture of the differences in air pressure that occur when air is being sucked into a pipe by an air pump i.e vacuum cleaner/M3 engine.


Quote:
Originally Posted by ace996 View Post
I do not think that zone/vent is allowing any positive pressure to be added to the airbox, on the contrary, I think it acts as a true vent...allowing pressure to be released out the box. Why else would rain fly out of the box or leaves poke out through the mest on the vent when driving?

On my vacuum cleaner, there is a little sliding vent on the solid connector to which the flexible pipe and the solid pipe for the end fittings attach, which can be opened to reduce the suction from the end of the pipe; I have yet to see anything blow out of this vent when opened, because the flow of air through the solid pipe from the suction tip towards the vacuum cleaner produces a "venturi effect" which always sucks air into the vacuum cleaner. I bet you NEVER see rain or leaves fly out of the hood vent under WOT.
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