Dump Valves, BOV's
Discussion
Hey folks. Looking for some help with Dump Valves and BOV's. I have an 05 plate STi Impreza and was thinking about fitting an aftermarket Dump Valve or BOV but a Ive heard that theyr not very good for the engine causing overfueling etc. Can anyone tell me whats the best one to fit to the car or the best kind, i.e hybrid 50/50, any info would be much appreciated.
cheers
cheers
Seriously, don't put anything other than a recirc valve on your Impreza, and the OEM one is more than capable.
This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Edited by Weso on Monday 14th July 09:58
As a rule of thumb- if it has an AMM (device that measures air volume in the intake- your Scooby has one) then either use a recirculating one- Bailey do one- or leave it stock. If it has a MAP sensor based engine management (most European stuff) then do what you want and it'll be fine.
No, there's no way of converting AMM to MAP, unless you want to change your entire engine management!
I've actually run an AMM based car with an HKS SSQV, but it takes some SERIOUS messing about wih the valve to set it up to work properly and really isn't worth the bother. The aftermarket recirc won't send your engine management into a strop and will sound 90% as good as a BOV.
No, there's no way of converting AMM to MAP, unless you want to change your entire engine management!
I've actually run an AMM based car with an HKS SSQV, but it takes some SERIOUS messing about wih the valve to set it up to work properly and really isn't worth the bother. The aftermarket recirc won't send your engine management into a strop and will sound 90% as good as a BOV.
Weso said:
Seriously, don't put anything other than a recirc valve on your Impreza, and the OEM one is more than capable.
This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Buy the correct one, and it will run fine...This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Edited by Weso on Monday 14th July 09:58
Some people take certain nonsense forums as gospel.....Sc*ahem*net..
Big problem with a lot of dump valves...either VTA or Re-circ.....is that most, despite their high price, are cheap s
te.stevieturbo said:
Weso said:
Seriously, don't put anything other than a recirc valve on your Impreza, and the OEM one is more than capable.
This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Buy the correct one, and it will run fine...This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Edited by Weso on Monday 14th July 09:58
Some people take certain nonsense forums as gospel.....Sc*ahem*net..
Big problem with a lot of dump valves...either VTA or Re-circ.....is that most, despite their high price, are cheap s
te.You pays your money you takes your chances.
But the bottom line is the Impreza runs a MAF based ECU, so it CANNOT run as well with a VTA BOV as it will with a recirc.
Weso
Weso said:
stevieturbo said:
Weso said:
Seriously, don't put anything other than a recirc valve on your Impreza, and the OEM one is more than capable.
This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Buy the correct one, and it will run fine...This has been done to death on all the Scooby forums, and the upshot is if you put a VTA on your car it will run like a bag of crap, and you could end up with major problems as a result of borewash etc.
I tried it to find out if all the talk was true by fitting one, and it was on my car for less than a week.
If you want a bit more pshhh, remove the intake resonator snorkus in the inner wing.
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Shortly someone will be along to say their car runs perfectly with a VTA and has for years, but IMHO don't do it.
Weso
Edited by Weso on Monday 14th July 09:58
Some people take certain nonsense forums as gospel.....Sc*ahem*net..
Big problem with a lot of dump valves...either VTA or Re-circ.....is that most, despite their high price, are cheap s
te.You pays your money you takes your chances.
But the bottom line is the Impreza runs a MAF based ECU, so it CANNOT run as well with a VTA BOV as it will with a recirc.
Weso
Closed throttle deceleration. When your foot is in the throttle, either valve should be closed anyway.
If it isnt, and its a VTA, the valve is a cheap POS or simply the wrong one for the application..
It is quite simple.
The other thing is, most BOVs default is effectively open to atmosphere when significant manifold vacuum exists i.e. when you are only on part-throttle. Much of the time in normal driving, IOW...
Given the amont of sh*t that can be drawn-in then, unless the BOV is filtered, this alone is really good reason to go for a recirc type... unless you just don't care about engine wear.
Given the amont of sh*t that can be drawn-in then, unless the BOV is filtered, this alone is really good reason to go for a recirc type... unless you just don't care about engine wear.
Huff said:
The other thing is, most BOVs default is effectively open to atmosphere when significant manifold vacuum exists i.e. when you are only on part-throttle. Much of the time in normal driving, IOW...
Given the amont of sh*t that can be drawn-in then, unless the BOV is filtered, this alone is really good reason to go for a recirc type... unless you just don't care about engine wear.
No this isnt an accurate assessment.Given the amont of sh*t that can be drawn-in then, unless the BOV is filtered, this alone is really good reason to go for a recirc type... unless you just don't care about engine wear.
The spring in the bov counteracts the manifold vacuum under all conditions except when the throttle is rapidly closed and boost from the still spinning turbo is backed up behind the throttle plate.
Vacuum is developed in the manifold which acts on the upper surface of the valve/diapraghm/piston, and boost pressure then overcomes the spring pressure as a result of the now high manifold vacuum.
If its opening at any other time it means that the spring pressure dosent match the boost level youre running, as vacuum alone should never open it.
Most recirculating piston types have a set screw to preload or adjust the spring and give you some control over what pressure it vents.
Air entering the system via a VTA isnt accounted for by a MAF system so effectively, if the bov is opening during "normal" unboosted driving what youre getting is an air leak. Not good.
Edited cos i cant spell vacuum....twice!
Edited by Deltaf01 on Thursday 17th July 08:48
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