PCV system
03-25-2003, 02:22 AM
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PCV system
In the grand scheme of things, this might seem pretty mundane, but as I reassemble the induction system of my car, I looked at the routing of the PCV system (if that's what it is), and wondered at the design. Anybody care to venture a guess as to why the line from the the left side of the throttle-housing (below the throttle body) that runs into the left intake plenum does not just result in a huge apparent vacuum leak into that plenum??
03-25-2003, 04:40 AM
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This bugged me for a long time too.
The way I understand it, the Venturi y-connector, just off the plenum, works to keep vacuum to the brake booster, climate control, and cruise even under sustained full throttle driving.
Normally, there is vacuum in the plenum. At full throttle, there is low to no vacuum, but the rush of air through the throttle body creates a Venturi effect vacuum in the y-connector.
The y-connector pulls apart (it has an o-ring inside that seals it), and the line from the TB has a reducer on the end of it.
The way I understand it, the Venturi y-connector, just off the plenum, works to keep vacuum to the brake booster, climate control, and cruise even under sustained full throttle driving.
Normally, there is vacuum in the plenum. At full throttle, there is low to no vacuum, but the rush of air through the throttle body creates a Venturi effect vacuum in the y-connector.
The y-connector pulls apart (it has an o-ring inside that seals it), and the line from the TB has a reducer on the end of it.
03-25-2003, 10:55 PM
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I don't get it...... at WOT there would be precious little pressure differential between the plenum and the pre-throttle region where that tap is. They are only a few inches apart and at WOT there is not much intermediate restriction.
The PCV routing on the right side of the engine doesn't do much for me either, but then again I don't understand the implications of that check-valve in the oil-filler casting vis-a-vis the pressure pulses in the crankcase. I wish I had an engineer to bother.
<img border="0" alt="[blabla]" title="" src="graemlins/a_smil17.gif" /> <img border="0" alt="[blabla]" title="" src="graemlins/a_smil17.gif" />
I could talk your ear off about intervertebral disc degeneration, or bio-mechanical performance enhancement, but this car stuff is sometimes VooDoo. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
The PCV routing on the right side of the engine doesn't do much for me either, but then again I don't understand the implications of that check-valve in the oil-filler casting vis-a-vis the pressure pulses in the crankcase. I wish I had an engineer to bother.
<img border="0" alt="[blabla]" title="" src="graemlins/a_smil17.gif" /> <img border="0" alt="[blabla]" title="" src="graemlins/a_smil17.gif" />
I could talk your ear off about intervertebral disc degeneration, or bio-mechanical performance enhancement, but this car stuff is sometimes VooDoo. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
03-26-2003, 12:12 PM
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brian,
Take a look at this link. you need flow, not pressure differential
<a href="http://www.hyvac.com/Products/O_pumps/Air%20Venturi/Air_Venturi_vacuum.htm" target="_blank">http://www.hyvac.com/Products/O_pumps/Air%20Venturi/Air_Venturi_vacuum.htm</a>
Take a look at this link. you need flow, not pressure differential
<a href="http://www.hyvac.com/Products/O_pumps/Air%20Venturi/Air_Venturi_vacuum.htm" target="_blank">http://www.hyvac.com/Products/O_pumps/Air%20Venturi/Air_Venturi_vacuum.htm</a>
03-26-2003, 03:17 PM
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The ignition vacuum advance works the same way.
Increased flow = more advance.
Increased flow = more advance.
03-26-2003, 03:57 PM
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"The PCV routing on the right side of the engine doesn't do much for me either, but then again I don't understand the implications of that check-valve in the oil-filler casting vis-a-vis the pressure pulses in the crankcase"
Is there a check valve in the oil filler casting? When I replaced the lower gasket on my oil filler, I did not see a check valve.
Is there a check valve in the oil filler casting? When I replaced the lower gasket on my oil filler, I did not see a check valve.
03-26-2003, 11:14 PM
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I found a check-valve embedded in the more forward of the 2 vertical spigots on the right side of that oil-filler casting. I don't know if the OB's have this same routing from the throttle-body and the forward cam-cover outlet through the oil-filler casting.