do most S4'ers here bypass the N249 solenoid and run directly off the manifold?
06-20-2005, 04:47 AM
#2
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Some have but probably not many.
I did briefly but I saw no difference between the two setups.
Note that just bypassing the N249 will throw a DTC/CEL as the vacuum reservoir is used for the evap system.
-Dave Pramanik
Note that just bypassing the N249 will throw a DTC/CEL as the vacuum reservoir is used for the evap system.
-Dave Pramanik
06-20-2005, 04:51 AM
#3
ok thanks for the info...
if i did bypass the N249, i'd tee the vac supply to it and the BPV, so the system wouldnt know the difference 
the reason im asking is that im chasing a performance gremlin. its seems every other day, i get lower boost accompanied by loud turbo whine. if the N249 is stuck or bad, im guessing that no signal is getting to the BPV to hold them shut.
the reason im asking is that im chasing a performance gremlin. its seems every other day, i get lower boost accompanied by loud turbo whine. if the N249 is stuck or bad, im guessing that no signal is getting to the BPV to hold them shut.
06-20-2005, 05:19 AM
#5
im planning on a pressure check soon...
the reason i dont think its a boost leak is that somedays i make full boost and the car pulls hard. turbo whine is much less.
i did vac test the BPV, and it actuated fine.
i did vac test the BPV, and it actuated fine.
06-20-2005, 05:22 AM
#6
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The BPV's default state is shut.
The N249's function is to hold some vaccuum in reserve so that the ECU can open the BPVs at any point (as a safety measure). By bypassing the N294, you only allow the BPVs to open when the engine is under vacuum.
I tend to think that the N249/vacuum reservoir wouldn't have sufficient vacuum to hold the BPVs open continuously, so I doubt that is your problem, but its easy enough to bypass and test out. I wouldn't even worry about teeing the vac reservoir for a quick test.
-Dave Pramanik
I tend to think that the N249/vacuum reservoir wouldn't have sufficient vacuum to hold the BPVs open continuously, so I doubt that is your problem, but its easy enough to bypass and test out. I wouldn't even worry about teeing the vac reservoir for a quick test.
-Dave Pramanik
06-20-2005, 05:49 AM
#7
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If you have a hose clamp that needs to be tightened on an IC or something...
or a pinhole somewhere, with a change in temperature those holes can seal or open or close back up. Same with a crack in the TBB.
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06-20-2005, 05:58 AM
#8
doesnt the BPV rely on boost pressure through its vac line to help keep it shut under boost?
if so, then a N249 that is not allowing boost to reach the BPV could cause the BPV to open under boost.
06-20-2005, 06:16 AM
#9
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The spring in the BPV should be sufficient to hold it closed.
It probably sees some manifold pressure as well, but the spring is stiff enough to do the job alone, I believe.
-Dave Pramanik
-Dave Pramanik
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