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Discussion Starter #1
Is my blowoff valve supposed to be open at idle with vacuum attached? My car pulls 22 in/lbs of vacuum at idle.
 

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Discussion Starter #3
That's what I thought. When I had my recharge on it was the same way.I just didn't know because the turbo isn't spinning as fast as the blower at idle.my tune needs to be reworked still thought.I thought the may wasn't seeing enough air at idle because it is go out at the blowoff.
 

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Discussion Starter #5
So.you saying it should be closed at idle?
 

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On my setup if i make the BOV shut at idle the turbo will surge at lower RPM/boost scenarios, if i lug it and make a few psi and let off it will surge a bit, if i'm higher in the RPMs when i let off the gas the vacuum is much higher and will open the BOV more and vent better. Id set it to where its a little bit open at idle or so. You want any vacuum over what you pull at idle to be opening the valve.
 

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yeah it's supposed to be. It shouldn't be a big issue to solve. Just check with the manufacture for your bov and order a stiffer spring.
 

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Discussion Starter #8
Thanks everyone.Ill have to check with on3 to see if I can get a stiffer spring.
 

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Gonna respectfully disagree. When I experienced this same problem I called Tial directly and the guy on the tech lines exact words were the Tial BOV should be CLOSED at idle, period, if you give it a little gas then it opens and closes again your fine anything else and you do not have the right spring inside. An example is if your vacuum is about 11in/Hg, you have to use the black spring, which [email protected] and is for vacuum between 10-13in/Hg.

Mass Air Sensor equipped car it is critical that the bypass valve be closed at idle. If it hangs open under idle conditions it can cause a few problems like stalling when you come back to idle. poor idle quality, and poor part throttle driveability.

Those were his words not mine.
 

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Discussion Starter #11
Thanks for the info.I will call tial today and see if I can get a new spring. I though with a turbo the bov is closed til revved up then closed again.it makes since why my car runs crappy at idle.plus I still have my blower tune. It just seemed like I wasn't getting enough air across the maf.
 

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Only if the BOV is after the air meter will it cause issues, if its before the meter there is nothing to worry about.

The best place for the BOV is before the MAF, if your going to run it after the MAF you have to recycle the blowoff air back into the airstream before the turbo. ( after maf)

So if you have your BOV after the meter even if the valve is shut at idle. it will still go rich when it does vent as your venting off metered air.

Ive experimented with my BOV and even ran the car with it off at idle. It does blow air, so the likelyhood of sucking something in is pretty small IMO. I think having the valve open at idle isnt a problem. I found having too stiff of a spring causes surge as you have a harder time pulling enough vacuum to fully open the valve. If i adjust my BOV to stay shut at idle i will see a slight surge at lower RPM boost situation, higher rpm isnt a problem as off throttle vaccum is really high.

Id say the goal is going to be keep the valve as shut as you can without surge issues from insufficient bleed off.
 

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Only if the BOV is after the air meter will it cause issues, if its before the meter there is nothing to worry about.

The best place for the BOV is before the MAF, if your going to run it after the MAF you have to recycle the blowoff air back into the airstream before the turbo. ( after maf)

So if you have your BOV after the meter even if the valve is shut at idle. it will still go rich when it does vent as your venting off metered air.

Ive experimented with my BOV and even ran the car with it off at idle. It does blow air, so the likelyhood of sucking something in is pretty small IMO. I think having the valve open at idle isnt a problem. I found having too stiff of a spring causes surge as you have a harder time pulling enough vacuum to fully open the valve. If i adjust my BOV to stay shut at idle i will see a slight surge at lower RPM boost situation, higher rpm isnt a problem as off throttle vaccum is really high.

Id say the goal is going to be keep the valve as shut as you can without surge issues from insufficient bleed off.


i 2nd that!!! very well put Brett


i ran into same issue's too with it open at idle. its not going to suck anything in, or make ur car ran bad. a stiffer spring may cause surging, which you dont want id leave it be. but thats just my 2cents, brett
 

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my turbo xs on my vortech car is not open at idle. It only opens up in neautral if i rev the car. With the car in gear and under load it opens up below 1/2 throttle to bleed off excess pressure. when i give it gas it closes until i shift gears. If yous is open at idle then id say u need a diff spring in it.
 

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Also, just noticed you said you are still on your blower tune. I'm assuming you just got the car together fairly recently right? DO NOT GO WOT with the blower tune!! You will have a ridiculous amount of denotation in the lower rpm's. Especially when you take into consideration your old tune probably has an exceptional amount of timing down low to compensate for the lack of boost.

Don't want you to tear up your ride
 

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Hahaha. This is quotable material for sig right here!!!

You are not sucking in air through an open bov. If you are then your turbo isn't spinnin.
Wick is correct! Your BOV is suppose to be open when sees vacuum. Like Wick said if turbo is spinning (and it should be at any RPM) their should be a positive pressure in intake pipe. If you put your hand on the outlet of the BOV you should feel air coming out. If you do not then there is something wrong. Your setup is correct and fine. As soon as you touch the throttle the BOV should close right away. Been using Turbos and Superchargers for 13 years and my BOVs all worked this way.
 

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Only if the BOV is after the air meter will it cause issues, if its before the meter there is nothing to worry about.

The best place for the BOV is before the MAF, if your going to run it after the MAF you have to recycle the blowoff air back into the airstream before the turbo. ( after maf)

So if you have your BOV after the meter even if the valve is shut at idle. it will still go rich when it does vent as your venting off metered air.

Ive experimented with my BOV and even ran the car with it off at idle. It does blow air, so the likelyhood of sucking something in is pretty small IMO. I think having the valve open at idle isnt a problem. I found having too stiff of a spring causes surge as you have a harder time pulling enough vacuum to fully open the valve. If i adjust my BOV to stay shut at idle i will see a slight surge at lower RPM boost situation, higher rpm isnt a problem as off throttle vaccum is really high.

Id say the goal is going to be keep the valve as shut as you can without surge issues from insufficient bleed off.

FoxFan88 is dead on!! Very well explained!
 

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Wick is correct! Your BOV is suppose to be open when sees vacuum. Like Wick said if turbo is spinning (and it should be at any RPM) their should be a positive pressure in intake pipe. If you put your hand on the outlet of the BOV you should feel air coming out. If you do not then there is something wrong. Your setup is correct and fine. As soon as you touch the throttle the BOV should close right away. Been using Turbos and Superchargers for 13 years and my BOVs all worked this way.QUOTE]

You should only feel air coming out when and only when it is blowing off extra BOOST!... Not when idling! Although the compressor may be barely spinning it is NOT creating boost at idle. it will still be in vaccum at idle and when in vaccum it will pull a vaccum (have suction)! Therefore if it is slightly open when idling it will have a vaccum leak! If it is slightly open under boost then you will have a boost leak! THe blow off valve should be closed at idle and all other times unless it is relieving excess boost pressure so you dont cause compressor surge ( blowing off)! That is the only purpose of the bov... to release all the extra boost when the throttle body or plates on carb close so it dont make the turbo backspin which can cause major damage

Ever unhooked a intercooler pipe and see how the car runs?
 

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Wick is correct! Your BOV is suppose to be open when sees vacuum. Like Wick said if turbo is spinning (and it should be at any RPM) their should be a positive pressure in intake pipe. If you put your hand on the outlet of the BOV you should feel air coming out. If you do not then there is something wrong. Your setup is correct and fine. As soon as you touch the throttle the BOV should close right away. Been using Turbos and Superchargers for 13 years and my BOVs all worked this way.QUOTE]

You should only feel air coming out when and only when it is blowing off extra BOOST!... Not when idling! Although the compressor may be barely spinning it is NOT creating boost at idle. it will still be in vaccum at idle and when in vaccum it will pull a vaccum (have suction)! Therefore if it is slightly open when idling it will have a vaccum leak! If it is slightly open under boost then you will have a boost leak! THe blow off valve should be closed at idle and all other times unless it is relieving excess boost pressure so you dont cause compressor surge ( blowing off)! That is the only purpose of the bov... to release all the extra boost when the throttle body or plates on carb close so it dont make the turbo backspin which can cause major damage

Ever unhooked a intercooler pipe and see how the car runs?
Mostly right. The impeller spinning at idle will most of the time be pushing more air than the engine is taking in at idle because of the throttle blades being closed. So unless you have a turbo charger to big for the engine and not spinning hardly at all at idle than you will have a slight positive air pressure in the intake tube and only the air-intake tube. When I say slight I mean like 0 to.1 psi or 99 to 100KPH This air will go where ever it can or if no outlet it will just slow the impeller down creating a very slight exhaust restriction in the exhaust side of the turbo. The BOV will be open because it is seeing vacuum. So the air will rush out of it being the lowest pressure area. The BOV opens because when the throttle blades shut it creates a vacuum which in turn the BOV sees this because it is plumbed to the intake after the throttle-body or carb. This means the rpm of the engine is trying to pull more air in than is available creating a vacuum. (All BOVs will be open when see any vacuum unless you put a stiffer spring in the BOV to keep it closed). Do not do this for it puts stress on the engine and the turbo and create extra exhaust pressure in the headers to the turbo. BAD BAD BAD don't do it!!!! Will not hurt it really at all but why put the extra issue into the equation.
 
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