View Full Version : Blow off valve ??? What ???
My friend and i had an argument about blowoff valves and thier purpose.
So now for some reason, im doubting myself and i was wondering if ya could explain it to me.
??? :dunno: :dunno: :dunno:
boi-alien
11-20-2002, 07:25 PM
what do u think a BOV does?!
i know what it does (kinda obivious ;) ) now why???
purpose baby purpose
GTS Jeff
11-20-2002, 08:56 PM
do a search foo.
infamous
11-20-2002, 08:58 PM
Blow Off Valve: a device used to release excess pressure in the intake system between the compressor wheel and the throttle plates, to prevent compressor surge.
Compressor Surge: a condition caused by compressed intake air caught between the compressor wheel and closed throttle plates. when you get off the throttle after a burst of acceleration, the plates close but the compressor wheel may still be sending compressed air into the system. if the compressed intake charge cannot flow through the throttle plates, i t will flow back to the compressor, which could result in bearing damage.
hehe good old super street....
Originally posted by Jeff TYPE R
do a search foo.
if you dont got anthing worth posting, dont post......... I mean, i asked a question, if you dont want to answere me, thats fine and i would care less because i wouldnt know about it. This is how i chose to get my info and for some reason you seem to have a problem with that :dunno: come on dude, keep it smooth
thanks infamous :thumbsup:
Autodream
11-21-2002, 01:28 AM
Infamous is right but let me add to that, in order for a turbo to creat full boost the shaft has to turn at over 50k rpm, small turbo may spin at over 100k rpm at full boost. during shift some time excess pressure can force the turbo to come to a complete stop or even cause the wheel to spin backward, 2 things can be bad here are, 1 you can damage the turbo, 2 it take time for the turbo to reach it operating speed again. By blow excess pressure out of the system, the turbo can mamtain it's speed during gear shifting. after all this it can sound cool too.
ecstasy_civic
11-21-2002, 01:57 AM
Infamous is right but let me add to that, in order for a turbo to creat full boost the shaft has to turn at over 50k rpm, small turbo may spin at over 100k rpm at full boost. during shift some time excess pressure can force the turbo to come to a complete stop or even cause the wheel to spin backward, 2 things can be bad here are, 1 you can damage the turbo, 2 it take time for the turbo to reach it operating speed again. By blow excess pressure out of the system, the turbo can mamtain it's speed during gear shifting. after all this it can sound cool too.
i couldnt have said it better myself:thumbsup:
GTS Jeff
11-21-2002, 02:09 AM
Originally posted by hjr
if you dont got anthing worth posting, dont post......... I mean, i asked a question, if you dont want to answere me, thats fine and i would care less because i wouldnt know about it. This is how i chose to get my info and for some reason you seem to have a problem with that :dunno: come on dude, keep it smooth
thanks infamous :thumbsup: u should take your own advice. and do a search while ure at it. there was a thread on THIS EXACT QUESTION a little while ago, and it is redundant to answer twice.
infamous
11-21-2002, 08:48 AM
Originally posted by sr20det95
Infamous is right but let me add to that, in order for a turbo to creat full boost the shaft has to turn at over 50k rpm, small turbo may spin at over 100k rpm at full boost. during shift some time excess pressure can force the turbo to come to a complete stop or even cause the wheel to spin backward, 2 things can be bad here are, 1 you can damage the turbo, 2 it take time for the turbo to reach it operating speed again. By blow excess pressure out of the system, the turbo can mamtain it's speed during gear shifting. after all this it can sound cool too.
also true. thanks for helping me on that one sr20det95! :thumbsup:
Ferio_vti
11-21-2002, 03:54 PM
BOV: Something every girlfriend should be equiped with.
Pole Position
11-21-2002, 10:05 PM
Let me add my 2 cents here...
turbos are free spinning, meaning that when there is no or not enough exhaust gas (letting off the gas) going through the turbine housing, the wheels still spin, thus boost is still being created. Compressed air is trying to go to the engine, but the throttle plate is closed and the air is being forced back to the turbo. This is where the BOV comes in. It relieves that extra pressure.
This is also why people buy turbo timer as well. Since turbo spins 10 - 15 times faster than the engine, the turbo wheels are still (free) spinning after the engine is shut off. It may take up to a few minutes until it stops. Picture this... metals rubbing against metals very fast with little lubrication for a few minutes.
rage2
11-22-2002, 10:03 AM
Originally posted by Pole Position
This is also why people buy turbo timer as well. Since turbo spins 10 - 15 times faster than the engine, the turbo wheels are still (free) spinning after the engine is shut off. It may take up to a few minutes until it stops. Picture this... metals rubbing against metals very fast with little lubrication for a few minutes.
Actually turbo timer's are used to circulate oil and/or coolant into the turbo to cool down the superheated oil that was sitting inside the turbo. If you don't cool it down, the oil breaks down, and on next startup will harm the shaft.
On my car (factory turbo) there's a water pump that circulates coolant through the system to cool it down, eliminating the need for a turbo timer (My factory turbo was replaced at 150,000miles, damage only from a nut that flew into the compressor). The turbos stops spinning quite quickly at idle... I actually have video of my car with the inlet exposed somewhere which shows the turbo stopping after 2 seconds. BB turbos will run a bit longer, about 5-10 seconds depending on size of turbo.
legendboy
11-22-2002, 10:10 AM
Originally posted by rage2
On my car (factory turbo) there's a water pump that circulates coolant through the system to cool it down,
Marc was telling me about that, we are going to rig something like that up on mine too!
Pole Position
11-22-2002, 05:33 PM
Originally posted by rage2
Actually turbo timer's are used to circulate oil and/or coolant into the turbo to cool down the superheated oil that was sitting inside the turbo. If you don't cool it down, the oil breaks down, and on next startup will harm the shaft.
On my car (factory turbo) there's a water pump that circulates coolant through the system to cool it down, eliminating the need for a turbo timer (My factory turbo was replaced at 150,000miles, damage only from a nut that flew into the compressor). The turbos stops spinning quite quickly at idle... I actually have video of my car with the inlet exposed somewhere which shows the turbo stopping after 2 seconds. BB turbos will run a bit longer, about 5-10 seconds depending on size of turbo.
So what you are saying is that turbo timers are pumping/supplying oil and coolant into the turbo? You kinda lost me there, because isn't turbo timers' job is to allow the engine to idle after you take the key out? By doing that, the engine still supply the turbo oil while the wheels slow down.
Yeah a lot turbo these days have solved the "coked oil" problem, eliminating the need of turbo timers. I never heard of your turbo design, but that's cool because now I learn. I know there is the semi-floating bearing design, but don't know exactly how it works.
turboMiata
11-23-2002, 03:53 PM
Originally posted by Pole Position
isn't turbo timers' job is to allow the engine to idle after you take the key out? By doing that, the engine still supply the turbo oil while the wheels slow down.
Yup. As long as the engine is a running, the oil is a pumping.
90_Shelby
11-23-2002, 03:58 PM
I wish I had a turbo that stayed spinning after I shut the car off for a few minutes:nut: :dunno:
redline_13000
11-25-2002, 06:29 PM
damn i knew some guy with a 92 5.0 stang...i would go up to his car maybe 10 min after he parked and could still hear the turbo...
Pole Position
11-25-2002, 11:28 PM
Yeah man, that's because the turbo is stil spinning.
4wheeldrift
11-26-2002, 07:47 AM
Originally posted by Pole Position
Yeah man, that's because the turbo is stil spinning. Its to allow the bearings in the turbo time to cool down. If oil isn't circulating, the heat in the turbo won't take long to break down the oil that is sitting stagnant in the turbo. Destroyed oil is VERY bad for the bearings in your turbo. Bearing failures are far less common now than they were, but it pays to be careful.
Pole Position
11-26-2002, 07:55 AM
Originally posted by 4wheeldrift
Its to allow the bearings in the turbo time to cool down. If oil isn't circulating, the heat in the turbo won't take long to break down the oil that is sitting stagnant in the turbo. Destroyed oil is VERY bad for the bearings in your turbo. Bearing failures are far less common now than they were, but it pays to be careful.
Yes they are getting less common, but I believe it is important to cool down after a hard run. It is good for pistons as well.
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