N112, vacuum leaks, and drivability... new findings (updated)
08-06-2006, 08:42 AM
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N112, vacuum leaks, and drivability... new findings (updated)
<center><img src="http://pictureposter.audiworld.com/5201/img_8745.jpg"></center><p>
a follow up to my earlier post, see link...
A check of JohnLZ7W's car for the same leak found a completely different design of the "cap" on the N112's unused nipple. This one leaks too (and John has no drivability problems). Under careful scrutiny it looks like it's supposed to leak. A controlled bleed off of sorts.
So, although sealing this to a "no leak" condition resolved a long term drivability problem with my car, it may not be appropriate for yours.
update: it's an apparent coincidence that plugging the leak changed anything on my engine... I've re-installed the "vent". Further study shows: it's there to "bleed off" the Combination Valve. The vacuum/pressure source from the intake manifold is completely isolated from the bleed path, internally by the N112. The bleed is there to dump vacuum from the Combi valve so it can close, once the (secondary air injection) warmup cycle is complete. The Combi valve would otherwise remain open, allowing backflow of exhaust through the valve and into the Secondary Air Pump.
Sorry for any confusion... Russ<ul><li><a href="https://forums.audiworld.com/tt/msgs/1530789.phtml">got lean surge?? spool up could be smoother?? G/sec kind of low??</a></li></ul>
a follow up to my earlier post, see link...
A check of JohnLZ7W's car for the same leak found a completely different design of the "cap" on the N112's unused nipple. This one leaks too (and John has no drivability problems). Under careful scrutiny it looks like it's supposed to leak. A controlled bleed off of sorts.
So, although sealing this to a "no leak" condition resolved a long term drivability problem with my car, it may not be appropriate for yours.
update: it's an apparent coincidence that plugging the leak changed anything on my engine... I've re-installed the "vent". Further study shows: it's there to "bleed off" the Combination Valve. The vacuum/pressure source from the intake manifold is completely isolated from the bleed path, internally by the N112. The bleed is there to dump vacuum from the Combi valve so it can close, once the (secondary air injection) warmup cycle is complete. The Combi valve would otherwise remain open, allowing backflow of exhaust through the valve and into the Secondary Air Pump.
Sorry for any confusion... Russ<ul><li><a href="https://forums.audiworld.com/tt/msgs/1530789.phtml">got lean surge?? spool up could be smoother?? G/sec kind of low??</a></li></ul>
08-06-2006, 10:16 AM
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Thanks for the update, btw, I was going to plug that hole but
found the same thing JohnLZ7W found so I left it the way I found it. Interesting.
<img src="http://images18.fotki.com/v330/photos/4/41970/1982850/pic029-vi.jpg">
<img src="http://images18.fotki.com/v330/photos/4/41970/1982850/pic029-vi.jpg">
08-07-2006, 10:10 AM
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Hey Steve, thanks.... I circled the N112 in black, under "zoom"
<center><img src="http://pictureposter.audiworld.com/34314/thing-vi.jpg"></center><p>the arrow pointing into the top suggests that air IS supposed to flow into the valve. Thanks for the pic... your source?
08-07-2006, 10:12 AM
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LOL...I have no idea where that came from..>
Just grabbed it once when I saw it....Did you see this post? Sounds like the N112....<ul><li><a href="https://forums.audiworld.com/tt/msgs/1533051.phtml">https://forums.audiworld.com/tt/msgs/1533051.phtml</a</li></ul>
08-07-2006, 10:16 AM
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Oh! Another thing that I'm wondering about....would you look at your car?
On both John's and mine the hose that runs from the N112 to the combination valve, terminates at the combi valve. There is no "T" or hose that continues on to the wastegate or charge control valve (I think the illustrator called it). Does your car have one of those?
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08-07-2006, 10:35 AM
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The mystery "T" and the hose from the combi valve to the waste gate
<center><img src="http://pictureposter.audiworld.com/34314/getimage.jpg"></center><p>
show up clearly in the Bentley too... maybe I'll hook one up and see what happens, assuming the nipple is there on the wastegate
show up clearly in the Bentley too... maybe I'll hook one up and see what happens, assuming the nipple is there on the wastegate