I need help for a future turbo install
05-27-2009, 05:59 PM
#26
As an example - I've seen over 15psi in the charge tube (just before the throttle plate) while manifold was at 0psi ....
In this scenario (which is a lot of the time BTW) a lot of air is going to be bypassing the throttle plate via the jet air hose. What effect this has I don't know . Possibly all it does is alter how much %throttle you need for a given load .
I can't see it being a good thing though .
Better in what sense ?
Last edited by Brettus; 05-27-2009 at 06:37 PM.
05-27-2009, 07:13 PM
#29
The JAB should ALWAYS see higher pressure than the manifold. Pretty simple concept. Already been over that a bunch of times on this forum over the last 3 years.
On the subject of BOVs - my HKS only opens when it sees relative vacuum in the intake manifold. That is the beauty of that valve.
I've since recirc'ed mine to get rid of the sogginess that happens from the MAF over-fueling that results from discharged, unmetered air.
05-27-2009, 10:10 PM
#30
Only if you are at full throttle - at anything other than full throttle you have a differential and how much differential you get is dependent on how your BOV is set up .
As an example - I've seen over 15psi in the charge tube (just before the throttle plate) while manifold was at 0psi ....
In this scenario (which is a lot of the time BTW) a lot of air is going to be bypassing the throttle plate via the jet air hose. What effect this has I don't know . Possibly all it does is alter how much %throttle you need for a given load .
I can't see it being a good thing though .
Better in what sense ?
As an example - I've seen over 15psi in the charge tube (just before the throttle plate) while manifold was at 0psi ....
In this scenario (which is a lot of the time BTW) a lot of air is going to be bypassing the throttle plate via the jet air hose. What effect this has I don't know . Possibly all it does is alter how much %throttle you need for a given load .
I can't see it being a good thing though .
Better in what sense ?
I don't see how I can have positive pressure in the charge tube and vacuum in the manifold when my BOV gets its reference from the manifold.
So the vacuum goes into manifold, which creates vacuum in the diaphragm of my BOV. But there is, lets say, 10psi in my charge pipe. 10psi beats 20" so the valve is forced open- this is how a BOV works.....
Holy crap, you have something set up wrong!
The JAB should ALWAYS see higher pressure than the manifold. Pretty simple concept. Already been over that a bunch of times on this forum over the last 3 years.
On the subject of BOVs - my HKS only opens when it sees relative vacuum in the intake manifold. That is the beauty of that valve.
I've since recirc'ed mine to get rid of the sogginess that happens from the MAF over-fueling that results from discharged, unmetered air.
The JAB should ALWAYS see higher pressure than the manifold. Pretty simple concept. Already been over that a bunch of times on this forum over the last 3 years.
On the subject of BOVs - my HKS only opens when it sees relative vacuum in the intake manifold. That is the beauty of that valve.
I've since recirc'ed mine to get rid of the sogginess that happens from the MAF over-fueling that results from discharged, unmetered air.
05-27-2009, 10:51 PM
#31
As far as the Jet air goes - if you have higher pressure in the charge tube than the manifold as I described - would you not think air is going to bypass the throttle plate and find its way in there ?
How is that different from other BOVs ?
Last edited by Brettus; 05-28-2009 at 12:15 AM.
05-27-2009, 10:57 PM
#32
I don't see how I can have positive pressure in the charge tube and vacuum in the manifold when my BOV gets its reference from the manifold.
So the vacuum goes into manifold, which creates vacuum in the diaphragm of my BOV. But there is, lets say, 10psi in my charge pipe. 10psi beats 20" so the valve is forced open- this is how a BOV works.....
The BOV i have was of the type that normally vents to atmosphere . This type of valve needs the differential to be high enough such that it won't leak at idle . Hence at partial throttle I was seeing high pressure in the charge tube because the differential was insufficient to crack the BOV .
Suggest you fit your boost gauge into the charge tube and see what happens at partial throttle under load - you just might get a shock . I've tried to get Kane to do it after an argument we had but he never found the time to do it .
Last edited by Brettus; 05-27-2009 at 11:03 PM.
05-28-2009, 03:20 AM
#36
Either I am missing something here or you didn't do your partial throttle test very well . I'll conceed that Its more likely that I'm am missing something so humour me with an explanation please .
If your BOV stays closed at idle - that means that there is insufficient vacuum to crack it open at 16-17"Hg . The charge tube press. is at zero so the differential has to be more than 16-17"Hg to crack the valve open . Correct ?
Now lets say you're under load and partial throttle IE accelerating reasonably hard in a higher gear (eg 3rd or higher) but not at full throttle .
The charge tube reaches say 10psi and the manifold is at 0psi . I know this is not scientific but the "differential" is now approx. same between the two sources as it was at idle so your bov should stay shut . In fact it will stay shut until it reaches the differential it needs to open .
If it opens as you suggested at only slightly higher pressure in the charge tube you will have very poor throttle response because you just dumped all the stored up pressure and the turbo would need to build it up again if you suddenly went WOT .
So what am i missing here ?
If your BOV stays closed at idle - that means that there is insufficient vacuum to crack it open at 16-17"Hg . The charge tube press. is at zero so the differential has to be more than 16-17"Hg to crack the valve open . Correct ?
Now lets say you're under load and partial throttle IE accelerating reasonably hard in a higher gear (eg 3rd or higher) but not at full throttle .
The charge tube reaches say 10psi and the manifold is at 0psi . I know this is not scientific but the "differential" is now approx. same between the two sources as it was at idle so your bov should stay shut . In fact it will stay shut until it reaches the differential it needs to open .
If it opens as you suggested at only slightly higher pressure in the charge tube you will have very poor throttle response because you just dumped all the stored up pressure and the turbo would need to build it up again if you suddenly went WOT .
So what am i missing here ?
Last edited by Brettus; 05-28-2009 at 03:37 AM.
05-28-2009, 03:44 AM
#37
Now lets say you're under load and partial throttle IE accelerating reasonably hard in a higher gear (eg 3rd or higher) but not at full throttle .
The charge tube reaches say 10psi and the manifold is at 0psi . I know this is not scientific but the "differential" is now approx. same between the two sources as it was at idle so your bov should stay shut . In fact it will stay shut until it reaches the differential it needs to open .
If it opens as you suggested at only slightly higher pressure in the charge tube you will have very poor throttle response because you just dumped all the stored up pressure and the turbo would need to build it up again if you suddenly went WOT .
So what am i missing here ?
The charge tube reaches say 10psi and the manifold is at 0psi . I know this is not scientific but the "differential" is now approx. same between the two sources as it was at idle so your bov should stay shut . In fact it will stay shut until it reaches the differential it needs to open .
If it opens as you suggested at only slightly higher pressure in the charge tube you will have very poor throttle response because you just dumped all the stored up pressure and the turbo would need to build it up again if you suddenly went WOT .
So what am i missing here ?
As soon as the manifold pressure nears atmospheric, the exhaust flow increases and the pressure shoots up in the charge tube and the pressure increases in the manifold.
If the turbo is held at the edge of surge and produces boost while the throttle is mostly closed, the BOV opens.
But this is really difficult to achieve with a properly sized turbo.
05-28-2009, 02:25 PM
#38
Did you mean to say improperly sized turbo or properly sized turbo ?
I tried to find a diagram of my BOV and failed but did find one of what you have - I think .
I can see this BOV is superior in design to what I have and will operate more quickly and with more finese due to the two stage operation.
Mine being a push type BOV has pressure directly onto the end of the piston from the charge tube and vacuum pulling from the other side of the piston .
Yours being a pull type has seperate chambers to push and pull the diaphram and thus open the valve .
However as far as I can tell it still operates on the same principles .That being that pressure differential between the intake and the charge tube is what activates it.
Looking at your valve I can't see why it should operate at a different pressure differential under partial throttle to what it does at idle . Can you ?
I tried to find a diagram of my BOV and failed but did find one of what you have - I think .
I can see this BOV is superior in design to what I have and will operate more quickly and with more finese due to the two stage operation.
Mine being a push type BOV has pressure directly onto the end of the piston from the charge tube and vacuum pulling from the other side of the piston .
Yours being a pull type has seperate chambers to push and pull the diaphram and thus open the valve .
However as far as I can tell it still operates on the same principles .That being that pressure differential between the intake and the charge tube is what activates it.
Looking at your valve I can't see why it should operate at a different pressure differential under partial throttle to what it does at idle . Can you ?
05-28-2009, 02:46 PM
#39
No. Properly. If the turbo is sized right, it wont be surging all the time.
It works on a differential, but that differential also references atmospheric, so the charge pipe must be above by a few PSI and the signal input must be in vacuum.
Its quite elegant and the reason why I use that particular valve on all of my systems.
Its quite elegant and the reason why I use that particular valve on all of my systems.
05-28-2009, 03:01 PM
#40
I'm not sure whether you even answered my question or not there -you are good at that .
Lets forget about your valve for a moment and concentrate on what I have which is more representative of what most people on the here will have as well .
Can you see why I get such a high pressure in my charge tube under light loads with my setup or do you just think I like to make **** up ?
Lets forget about your valve for a moment and concentrate on what I have which is more representative of what most people on the here will have as well .
Can you see why I get such a high pressure in my charge tube under light loads with my setup or do you just think I like to make **** up ?
05-28-2009, 04:00 PM
#41
This has really turned into a BOV discussion now and should be taken to another thread, LOL, instead of in the OPs thread
05-28-2009, 04:05 PM
#42
At idle your charge tube is in vacuum as well, so there is NO differential, which is why the valve doesn't open. Most BOV's also have springs to keep some light tension on the valve to help hold it shut.
This has really turned into a BOV discussion now and should be taken to another thread, LOL, instead of in the OPs thread
This has really turned into a BOV discussion now and should be taken to another thread, LOL, instead of in the OPs thread
And sorry to the OP for hijacking the thread ..... If there was some way we could take all these posts into another thread about BOVs I'm all for it ...
Last edited by Brettus; 05-28-2009 at 04:11 PM.
05-28-2009, 05:01 PM
#44
Just had a read of this . Looks like it goes to the charge tube on any installation where you run more than 7psi ......
http://www.synapseengineering.com/pdf/bov-manual.pdf
http://www.synapseengineering.com/pdf/bov-manual.pdf
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