Wierd Question
- Thread starter laloosh
- Start date
- :
- 2007 MS3
Obvious question here. Why don't you just ask Forge? Patty is usually pretty good about getting back to people.
yeah he's got a point, patty seems to be "in the know"
I'm sure a large part of the VTA design was to make it sound different, and probably flow differently, since the requirement of shooting air through a specific diameter hose in a specific direction was no longer an issue.
I'm sure a large part of the VTA design was to make it sound different, and probably flow differently, since the requirement of shooting air through a specific diameter hose in a specific direction was no longer an issue.
subparpunk03
Member
it might have something to do with the recirc valve not fully closing at idle. I'm not sure if it does or not. I know that if you have a recirc valve that sits open until boost is made then it will pull some air in directly to the cold pipe that is not measured by the MAF and you will run extremely lean.
Again, I don't know for sure if this is the case with the forge valve, just something to think about.
Again, I don't know for sure if this is the case with the forge valve, just something to think about.
patty AT forge
Member
The recirc valve will be an enormous leak at idle if installed VTA. The VTA valve has a secondary piston that remains sealed at idle...
SilverWagon
Banned
- :
- 2008 MS3
Patty if the valve leaks at idle, what prevents it from leaking under boost? It certainly should not be leaking at all.
SPEED3TYPE2
Member
that pipeing looks clean
SilverWagon
Banned
- :
- 2008 MS3
So the valve will leaks at idle and crusing conditions, but not under boost? How?
If the pressure behind the valve (vacuum line) is less than the pressure on the other side (air stream) it should open...how much the difference needs to be is probably related to the tension of the spring, etc. lol at least this is how it makes sense to me, but I could be wrong. I'm not an expert in this stuff, but physically it makes sense.
When cruising the difference may not be great enough. I'm just going to shut up until someone can answer this better.
When cruising the difference may not be great enough. I'm just going to shut up until someone can answer this better.
lolz looked it up I think i have the general idea down:
How it works: The usual arrangement is to have the pressure side of the valve attached to the pipe between the turbo and the throttle, and a vacuum hose on the top of the valve hooked up to the inlet manifold after the throttle body. A spring holds the valve shut. When you are on the throttle, the pressure in the turbo piping and the inlet manifold is equal, meaning that the pressure on each side of the valve is the same and therefore cancels itself out, leaving the spring holding the valve shut. When you lift off the throttle, you have high pressure in the turbo piping, and a vacuum in the inlet manifold. The pressure on the bottom of the valve and the vacuum on the top combine to lift the valve open and release the pressure in the turbo piping, since it can no longer go into the engine.
Pretty sure the stock bpv is open at idle...aftermarket hybrids and VTA valves need stiffer springs im pretty sure to keep it closed to air isnt leaked. But this is all really unrelated to the valve 'leaking' when you're on the throttle.
How it works: The usual arrangement is to have the pressure side of the valve attached to the pipe between the turbo and the throttle, and a vacuum hose on the top of the valve hooked up to the inlet manifold after the throttle body. A spring holds the valve shut. When you are on the throttle, the pressure in the turbo piping and the inlet manifold is equal, meaning that the pressure on each side of the valve is the same and therefore cancels itself out, leaving the spring holding the valve shut. When you lift off the throttle, you have high pressure in the turbo piping, and a vacuum in the inlet manifold. The pressure on the bottom of the valve and the vacuum on the top combine to lift the valve open and release the pressure in the turbo piping, since it can no longer go into the engine.
Pretty sure the stock bpv is open at idle...aftermarket hybrids and VTA valves need stiffer springs im pretty sure to keep it closed to air isnt leaked. But this is all really unrelated to the valve 'leaking' when you're on the throttle.
patty AT forge
Member
Its all about pressure differentials. Most all proper recirc valves will be open at idle whichis why they are note suited for use VTA, many cheaper VTA valves are also open at idle and are only usable on MAP based cars.
There are several strategies to keep a valve closed at idle: tuned leaks, stiffer springs, dual pistons, etc.
Vacuum will lift the valve open if it is greater than the cracking pressure of the valve spring combined with positive pressure in the charge piping (if any).
" the pressure in the turbo piping and the inlet manifold is equal, meaning that the pressure on each side of the valve is the same and therefore cancels itself out,"
This statement isn't entirely true. There will always be some amount of pressure drop and latency, this is where the performance benefit of our valve comes into place.
There are several strategies to keep a valve closed at idle: tuned leaks, stiffer springs, dual pistons, etc.
Vacuum will lift the valve open if it is greater than the cracking pressure of the valve spring combined with positive pressure in the charge piping (if any).
" the pressure in the turbo piping and the inlet manifold is equal, meaning that the pressure on each side of the valve is the same and therefore cancels itself out,"
This statement isn't entirely true. There will always be some amount of pressure drop and latency, this is where the performance benefit of our valve comes into place.
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