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Old 12-02-2003, 11:47 PM   #7
lotusTT
Scooby Specialist
 
Member#: 23359
Join Date: Aug 2002
Chapter/Region: NESIC
Location: San Francisco
Vehicle:
2002 BMW M Coupe
Steel Gray

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I believe he's describing a problem with having the line hooked up after the throttle body. It doesn't have anything to do with gas laws. When at say 20% throttle, the turbo is making say 15psi. The throttle body is only open a small amount, so only 2psi are getting through it, kinda like a check valve. When you open the throttle 100%, the pressure inside the throttle body and "charge pipe" equalize and the turbo output drops back to 4.5psi. The only downside is that your turbo is blowing 15psi when you're only using 2psi. If you connect the line to the turbo outlet, you get less boost (pressure drop from IC isn't accounted for) and a tiny bit more lag. If you connect the line to the manifold, you get more boost (no pressure drop) and less lag (the turbo's always making as much boost as it can, the throttle body just isn't letting by) but you are putting extra wear and tear on the turbo. I'm not sure it really makes that much of a difference on life, but I guess it depends on what turbo you're using and what its efficiency range is.
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