Blow Offs
- Thread starter aidanair
- Start date
I have a type RS, and LOVE IT. the way it butterflies and whooshes depending on throttle. Lol its so neat.
Adjuster
Supramania Contributor
I use two Bosch bypass valves. Don't remember the numbers, but they are off a Porsche 996 Turbo IIRC, and they were 30.00 for both.
Here is the key.
They must be installed the right direction.
I see people with them installed wrong all the time, and those same people complain they leak or don't hold boost.
Here is the key. They are designed to open under any vac conditions. If you have them plumbed correctly, this allows air to take a short cut around your turbo, FMIC and all the pipes/hoses. This shortcut improves throttle response at low engine speeds where there is no boost yet.
As soon as pressure exceeds ambiant, the bypass valve closes up, and is held closed by the pressure in the IC pipes. IT CAN NOT OPEN UP UNLESS THE VALVE BREAKS. And that would take pressures beyond what your engine would hold anyway.
The Bosch bypass valve has to be installed with the hose going to your IC pipe off the side of the body, and the hose that goes straight down, to your Accordian/intake hose. (Opposite the vac line fitting.)
It fits better backwards, but it only works right when it's installed the way I just noted.
Here is an old pic of my old setup. (I use two of them to get maximum air bypass, so it improved low speed throttle response. It works.)
Here is the key.
They must be installed the right direction.
I see people with them installed wrong all the time, and those same people complain they leak or don't hold boost.
Here is the key. They are designed to open under any vac conditions. If you have them plumbed correctly, this allows air to take a short cut around your turbo, FMIC and all the pipes/hoses. This shortcut improves throttle response at low engine speeds where there is no boost yet.
As soon as pressure exceeds ambiant, the bypass valve closes up, and is held closed by the pressure in the IC pipes. IT CAN NOT OPEN UP UNLESS THE VALVE BREAKS. And that would take pressures beyond what your engine would hold anyway.
The Bosch bypass valve has to be installed with the hose going to your IC pipe off the side of the body, and the hose that goes straight down, to your Accordian/intake hose. (Opposite the vac line fitting.)
It fits better backwards, but it only works right when it's installed the way I just noted.
Here is an old pic of my old setup. (I use two of them to get maximum air bypass, so it improved low speed throttle response. It works.)
Blow off valves arent rated to a certain pressure becuase the pressure is equal on both sides when in boost. unless the physical housing cant take it it will be fine.
depends upon design
the HKS Racing Type 2 and SSQV are both pull style, the boost will hold it closed. Many other brands use a push type that boost can push open, meaning you have to dick with the adjusting screw so it doesn't leak. If that doesn't work, you have to go with a stiffer spring...
the HKS Racing Type 2 and SSQV are both pull style, the boost will hold it closed. Many other brands use a push type that boost can push open, meaning you have to dick with the adjusting screw so it doesn't leak. If that doesn't work, you have to go with a stiffer spring...
if you buy the kit it comes with a pipe that replaces the plastic pipe that goes across the turbo...
Poodles said:
True, but they still have the vac line to the other side of the piston thats attached to manifold pressure, meaning boost on both sides. the diffrence is that the pistons moves in the direction of the boost pressure rather then against it. with the vac line disconnected it could push it open but with the vac line connected it will have boost pressure on both sides, plus the weight of the spring holding it closed.
I think the adjusting screw just controls what amount of vac/boost is needed to open it up, like a preload. That way if its tight it will take say 15in/hg of vac on one side and 8 psi on the other to open up, but if set loose it will only take 10in/hg on one side and 2psi on the other to open it up.
As long as theres a vac line connected to the valve it will equilize under WOT.
Then again below WOT when theres boost in the charge pipes but the throttle plate isnt open enough to see positive manifold pressure, it COULD creep open....
whole lot of variables as to why they leak, that's one of the reasons I like pull style BOV's...
to each their own I guess, but there is a reason HKS's BOV's sell so damn well...
to each their own I guess, but there is a reason HKS's BOV's sell so damn well...
speed dodici said:
i have a greddy rs too, and i love it. here it is on a stock ct setup. i had this venting to the atmosphere with no ill effects.
http://www.supramania.com/forums/showthread.php?t=50912
now that i have a big single and its converted to map, it flutters and sounds like a race car! i love it. the only other bov i would consider getting is a tial. they are so hot right now! :love: