vented blow off valve question
02-25-04, 11:09 PM
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vented blow off valve question
hey, i have my stock bov vented to the atmosphere and was wondering if air is supposed to be blowing out at idle cause it is on mine.its not as loud as when im driving and let off the gas, but you can hear it over the engine if your standing near it. my boost gauge reads like 17 vac at idle, isnt that what its supposed to be? just making sure everything is ok.
thanks,
craig
thanks,
craig
02-25-04, 11:15 PM
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I got this off of another post, I think its what you are looking for in a nut shell.
Originally posted by xstacy7
The stock BOV stops venting at 4 in./hg during vacuum -> boost transaction, and vice versa...starts to vent during boost -> vacuum transaction at 4 in./hg. When you accelerate and the pressure goes from vacuum to boost, as long as the vacuum has to overcome 4 in./hg, there is air being vented from the blow-off valve. As 4 in./hg arrives, the valve is closed and no air escapes through the y-pipe where the bov vents from. This also means while idling the blow-off valve will be venting as you will probably** be around 15-20 in./hg depending on your port/compression/modifications, etc...
The stock BOV stops venting at 4 in./hg during vacuum -> boost transaction, and vice versa...starts to vent during boost -> vacuum transaction at 4 in./hg. When you accelerate and the pressure goes from vacuum to boost, as long as the vacuum has to overcome 4 in./hg, there is air being vented from the blow-off valve. As 4 in./hg arrives, the valve is closed and no air escapes through the y-pipe where the bov vents from. This also means while idling the blow-off valve will be venting as you will probably** be around 15-20 in./hg depending on your port/compression/modifications, etc...
02-26-04, 12:43 AM
#3
Rotary Freak
xstacy7 has a stock bov that has the spring changed so it is closed at idle .It opens at 17 inches,so no air is wasted at idle and tip in .PM him for info and ask if he can tell the differance . Two other modified valves are in use but I do not know who has them .
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