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Here is some information about the GFB diverter, some might find it useful.
The questions are answered by the valve manufacturer.
> I was wondering if it is possible to install the GFB hybrid diverter
> valve on my car. I know you do not market the product for Saab
> automobiles but I hope you could be so keen and help me out.
It's a matter of packaging. It really depends on the space available in your engine bay. Some Saabs (like the new 9-3), have the stock valve right in front of the radiator and up high. Some don't.
>
> Here are a few question for which I could not find answars for in the
> product FAQ.
>
> 1.Is the atmospheric valve outlet open when ever the recirculating
> outlet is? The Cut-away picture gives the impression it is.
The valve is a piston design. The recirculating port and the venting port are offset by 4mm, with the recirc port being lower on the valve body. This makes the valve a staged design.
> 2.Does the
> atmospheric outlet have a filter to prevet dust from entering
> mainfold. Dust may enter the mainfold at idle when valve is open and
> mainfold pressure is below atmospheric pressure.
No filter is included. The valve should be adjusted so the piston is in the closed position at idle, with no air being drawn in at all. There is a spring pressure adjustment used to setup the valve properly during initial installation.
> What is ment be "allowing some air"? I'am having difficulties to
> believe that pressurised air from the mainfold would actually be
> plumbed back because pressurised air will burst toward the area with
> smallast resistance and that would be the atmospehere in this case?
Bosch Motronic engine management doesn't take kindly to blow-off valves that dump 100% of the metered air into the atmosphere. This can cause a rich fuel condition. Eventually, the ECU will throw a fault code for "Long Term Fuel Trim Rich". With the GFB Hybrid, this isn't the case. The valve primarily functions as a diverter valve during most part throttle driving. This is due to the recirculating port being lower than the vent port. When a high vacuum condition occurs (when shifting under boost), the piston in the GFB valve will travel upward enough to first divert air back into the turbo air intake and then the vent air to atmosphere. So, the path of
least resistance is the recirculating port. Hope that makes sense. By keeping some of the diverted air in the system, the fuel trim will remain stable (avoiding a rich condition).
> Do you have any test result what really happens in the engine when
> some air is vented to atmosphere when shifting under boost. My worries
> are that the engine will run rich momentarily, do to the lower amount
> of air in the systems compared to what ECU knows of, or does the ECU
> have a way to cope with this. If this is the case wont it destroy the
> catlic converter in the long run.
I think you should stay with a diverter valve if you have such great concerns. We offer the GFB Plumback valve which is simply a Hybrid valve without the venting port. It's $139.99, and recirculates 100% of the air. It can be adjusted to hover open at idle.
posted by 192.89.9...
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